Chapter 44: Cervical Spine Fractures and Dislocations

Andrew J. Schoenfeld, Christopher M. Bono

Chapter Outline

Introduction to Cervical Spine Fractures and Dislocations

Injuries to the cervical spine frequently occur following trauma and are becoming increasingly more common. They are estimated to occur in 2% to 3% of all patients who sustain blunt trauma,145 and population adjusted rates for these injuries were found to increase by 74% from 1997 to 2006.17 The total cost of health care associated with the acute management of cervical spine trauma in the United States exceeded 1 billion dollars in 2006 and undoubtedly will continue to increase in the immediate future.17 In the United States, most of the costs associated with cervical spine trauma are borne by federal health care programs, and the majority of care (73%) is currently provided by academic institutions. 
Although advances in perioperative care, surgical instrumentation, and understanding of the pathophysiology of trauma have engendered new treatment paradigms for these injuries within the last two decades, cervical spine fractures, dislocations, and spinal cord injury are by no means recent phenomena. The Ancient Egyptians appreciated such injuries and the Edwin Smith Papyrus, published about 2500 bc, stated that “If thou examinest a man [and] find him unconscious of his two arms … his two legs … (and) urine drops … without his knowing it … it is a dislocation of a vertebra of his neck …”.156 Hippocrates and Galen both described the chronic sequelae of spinal cord injuries, and the Byzantine Paul of Aegina was the first to postulate surgical decompression for the treatment of spinal fractures.156 The Renaissance surgeon, Fabricius Hildanus, developed the concept of open reduction for cervical fractures and dislocations in the seventeenth century,156 and one of the first such procedures performed in the United States was conducted by Dr. William W. Keene following the Battle of Gettysburg (1863).208 
More recent advances relate to an increased appreciation of the potential importance of early surgical decompression following spinal cord injury, biomechanical optimization of fixation constructs in osteoporotic or hyperostotic bone, and the impact of age and medical comorbidities on outcomes following injuries to the cervical spine. The effective treatment of cervical spine trauma is predicated on a comprehensive appreciation of factors as diverse as injury detection, description, classification, and an evidence-based approach to decision making and management. This chapter endeavors to address all the commonly recognized injuries of the cervical spine. In the upper cervical region [occiput (C0) to the axis (C2)], injuries include occipitocervical dislocations, occipital condyle fractures, atlas (C1) fractures (e.g., Jefferson-type burst fractures), atlantoaxial instability or rotatory dislocations, and C2 fractures (e.g., odontoid or bilateral pars interarticularis fractures). Subaxial injuries of the cervical spine (C3–C7) frequently include burst fractures, facet dislocations, so-called “teardrop” (flexion–compression) fractures, isolated facet, and simple spinous process fractures. 

Epidemiology of Cervical Injuries for Cervical Spine Fractures and Dislocations

Until recently, difficulties defining a population at risk or ensuring a catchment area in which all cases of cervical spine trauma could be definitively identified limited the capacity to describe the epidemiology of these injuries. What estimations were available were biased because of the location or study setting of the analyses. The incidence of cervical spine injury in the National Emergency X-radiography Utilization Study (NEXUS) was reported to be 2.4%.104,214 Limiting inclusion to those presenting at American trauma centers may increase the incidence of cervical spine trauma to the 2% to 4% rate commonly cited.145 
In a recent investigation, the incidence of cervical spine fractures within the American military was 0.29 per 1,000 per year over a decade (2000 to 2009).214 In a similar study, the same group found the incidence of spinal cord injury to be 429 per million.213 Within civilian populations, the incidence of spinal cord injuries may be lower, reportedly in the range of 40 per million.119,145,213 Male sex, white race, younger age, and socioeconomic status have been identified as independent risk factors for cervical spine trauma in several studies, although analysis of the whole population indicates that cervical fractures have a bimodal distribution affecting both younger and older patients (Table 3-13).111,213 
The upper cervical region is thought to be the most frequent site of fracture.118,120 However, associated spinal cord injury is less common as compared with subaxial injuries, presumably due to increased spinal canal diameter. Within the subaxial region, approximately 40% of all injuries are localized to C6 or C7. This area is also commonly involved in extension-type injuries encountered in the setting of hyperostosis [ankylosing spondylitis (AS) or diffuse idiopathic skeletal hyperostosis (DISH)].212,256 
Overall, acute mortality following cervical spine trauma has remained in the range of 2.5% since the 1990s, although the death rate may exceed 10% for those with spinal cord involvement.17 However, some studies have identified cervical fractures as a key event in the elderly, similar to hip fractures, in terms of their influence on morbidity and mortality.118,190,211 For example, in a large series of patients aged 65 years and older, Harris et al.118 cited a 3-month mortality rate of 19% following cervical fracture, irrespective of treatment. This statistic approached 30% 1-year postinjury, and those aged 85 years and older were found to have a mortality risk three times higher than the expected population-based death rate for their age cohort.118 

General Principles of Management of Cervical Spine Fractures and Dislocations

Mechanism of Injury for Cervical Spine Fractures and Dislocations

Cervical spine fractures and dislocations are known to occur in a bimodal distribution. In young, active patients, the mechanism of injury is most commonly high-energy trauma, such as a motor-vehicle accident or fall from height, although penetrating injuries are of increasing concern.32,86 Among a series of more than 1,000 patients with cervical spine injury, motor-vehicle/motorcycle accident was the cause in more than half of all cases.60 Falls were responsible for 23% of injuries and assault/violence occurred in 3%. 
In the elderly, low-velocity falls are the most frequent cause of cervical spine fracture. However, especially in those elderly patients with hyperostotic conditions of the spine, the resulting damage may be as severe as that encountered in high-energy injuries, although the mechanism may be apparently more benign. A high level of suspicion must be maintained by the treating practitioner. 

Prehospital Care for Cervical Spine Fractures and Dislocations

The initial management of patients with suspected spinal trauma begins at the point of injury. As many patients with cervical spine injury also have other, potentially serious, injuries, it is possible to miss cervical fractures or dislocations. The risk of neurologic sequelae increases by a factor of 10 if a cervical injury is missed,10 illustrating the importance of vigilance and a methodological approach to prehospital assessment and evaluation of the cervical spine in any patient at risk. To facilitate this process, the advanced trauma life support (ATLS) protocols of the American College of Surgeons provide guidelines that seek to mitigate the potential for delayed or missed diagnoses of cervical injuries. It is important to note, however, that the ATLS guidelines were never intended to ensure complete detection or description of all possible cervical spine injuries. 
ATLS protocols maintain that the cervical spine should be immobilized during the initial vital assessments, including evaluation of a patient’s airway, breathing, and circulatory status. Initially, manual immobilization should be undertaken until a hard cervical collar can be applied. If a hard collar is not available, the head can be secured to a stretcher using sandbags and tape. Most cervical collars intended for use in the trauma setting will have an anterior window that enables access to tracheostomy or emergent cricothyroidotomy sites. Although clinical differences remain to be documented, the NecLoc cervical orthosis has been found to allow less motion than many other devices, including the Aspen, Miami-J, and Philadelphia collars.15 
Maintenance of hemodynamic parameters and preservation of the airway are vital to any injured patient. It is important to understand that aggressive attempts at tracheal intubation or central line placement may increase the risk of further displacement and neurologic decline in patients with unstable cervical injuries. When attempting tracheal intubation, manual in-line stabilization of the cervical spine should be performed. In the event that an unstable cervical injury is suspected and deemed to preclude safe tracheal intubation, bag-mask ventilation can be continued until the patient reaches a hospital setting221 or emergent cricothyroidotomy may be performed.24 
Motorcycle helmets, as well as those used in sporting activities, should be maintained in position during the initial evaluation and en route care.227 Ideally, the helmet should be left in place until radiographic evaluation of the cervical spine is performed. This is facilitated by the fact that most modern motorcycle and football or hockey helmets allow for independent removal of the facemask or visor to facilitate access to the face and mouth while the helmet itself remains in place. 

Hospital Care for Cervical Spine Fractures and Dislocations

Resuscitation

Upon arrival in the trauma bay of an emergency room, an injured patient should be assessed using the ATLS guidelines and any lifesaving interventions should be performed. During initial evaluation, the patient’s cervical spine must remain immobilized in a cervical collar with manual in-line stabilization performed during transfers and at any time the collar is removed.70 Spinal precautions and logroll maneuvers should also be utilized. However, it is important to note that these do not always prevent spinal injury. Research has demonstrated an association between neurologic deterioration after spinal injury and excessive manipulation.122 Cadaveric studies have shown that motion occurs in unstable cervical spine injuries during logroll maneuvers.72 
In the patient with spinal cord compromise, it is imperative to maintain hemodynamic stability and perfusion of the cord. The systolic pressure should be kept above 100 mm Hg and the mean arterial pressure above 85 mm Hg.120,246 An individual with spinal cord injury may present to the emergency room in neurogenic shock. If this occurs, unlike in hemorrhagic shock, the patient will be hypotensive as well as bradycardic. Neurogenic shock results from a disruption of sympathetic pathways and not from a loss of intravascular volume. Therefore, if the patient is treated with fluid replacement, life-threatening pulmonary edema could occur. The hypotension of neurogenic shock should be treated by maintaining the patient in the Trendelenburg position and by the administration of vasopressors together with careful use of intravenous fluids.120 
Until recently, it was considered standard of care to initiate high-dose methylprednisolone therapy as described in the North American Spinal Cord Injury Studies when a spinal cord–injured patient presented, within 8 hours, as a result of blunt trauma.119,145 However, as the North American Spinal Cord Injury Studies trials have undergone increased scrutiny, concerns have been raised regarding the fact that methylprednisolone did not, in fact, show a significant benefit over placebo in the study’s primary outcome measure.145 A number of societies have issued statements that describe steroids in this scenario as a treatment option but they should not be considered standard of care.119 Inmany instances, such as in the elderly, the risks of high-dose steroid administration may be higher than the likelihood of substantial clinical benefit.119,129 In a recent prospective study involving 79 patients with spinal cord injury, Ito et al.129 found that the rate of neurologic improvement was higher in those treated without steroids (63%) than in those in whom the North American Spinal Cord Injury Studies protocol was followed (45%). Those individuals who received steroids were found to be at a significantly increased risk of infection. Importantly, all patients in this study were treated with surgical decompression and stabilization at the earliest clinical opportunity. 

History and Physical Examination of Cervical Spine Fractures and Dislocations

Following emergent stabilization and a primary survey, the patient with a suspected cervical spine injury should be evaluated with a detailed history and physical examination. If the patient is alert and able to participate, he or she should be questioned regarding previous injuries, whether there is a significant spinal surgical history, the events surrounding the present injury, the location of pain, and any perceived sensory or motor deficits. If the patient is obtunded or has sustained other serious injuries such as a long-bone fracture or an abdominal injury, he or she may be unable to completely answer questions or identify other sites of injury. In such cases, witnesses or first responders should also be interviewed. 
The mechanism of injury (e.g., fall from height, low-velocity fall with hyperextension of the cervical spine), direction of impact, and associated injuries (e.g., facial fractures, blunt head trauma, calcaneal fractures) or symptoms can assist in raising the level of suspicion concerning spinal trauma. One study found that the presence of a pelvic fracture increased the risk of cervical spine injury by a factor of 9.60 Respiratory impairment may suggest a high cervical injury or a fracture of the third cervical vertebrae.190 
Once an injury is identified in one spinal zone, all other regions must be examined both clinically and radiographically. The oft-quoted statistic of noncontiguous spinal fractures in 10% to 15% of trauma patients was recently confirmed in a retrospective 10-year review of cases treated at Yale-New Haven Hospital.169 If penetrating injury has occurred to the spine, an effort should be made to discern whether this resulted from a sharp object or gunshot. If it is a gunshot injury, it should be ascertained whether it was caused by high-velocity or low-velocity munition. 
A standardized, systematic spinal evaluation should then be performed. Ideally, the examination should begin in the cervical region and proceed distally. Alternatively, if a spinal zone is already known to be injured, this region should be examined last. The orientation of the head should be examined, as fixed rotation may indicate a unilateral facet dislocation. Areas of ecchymosis or open injury should be noted. Finally, the spinous processes and paraspinal musculature should be palpated and areas of pain, crepitation, or deformity recorded. 
A thorough neurologic examination follows palpation of the spine. If the patient is obtunded, this evaluation may be limited to observation of spontaneous motor function, withdrawal from noxious stimuli, determination of rectal tone, and assessment of the bulbocavernosus reflex. In an alert patient, the examination can be more complete and consists of cranial nerve examination as well as motor, sensory, and reflex examination in all dermatomal and myotomal distributions (Table 44-1). Cranial nerve impairment, particularly in the lower cranial nerves, can occur in occipital condylar fractures and other upper cervical spine injuries.58 
Table 44-1
Myotomes (Motor) and Dermatomes (Sensory) Should Be Serially Tested by a Single Examiner in Uniform Fashion
Motor Sensory Reflex
C5 Deltoid Lateral shoulder/lateral arm Biceps
C6 Biceps/wrist extension Lateral forearm/thumb and index finger Brachioradialis
C7 Triceps/wrist flexion Middle finger Triceps
C8 Hand intrinsics/finger flexors Ring and little finger/medial forearm
T1 Hand intrinsics/finger abduction Medial arm/axilla
S5 Rectal tone Perianal Bulbocavernosus
X
Sensation is assessed on a 3-point scale (normal, decreased, or absent) and motor function is graded from 0 to 5 (Table 44-2). Sensory and motor deficits are conventionally combined to give a grade and motor score (Table 44-3). The presence of a complete (no sensory or motor function below the level of injury) or incomplete (some sensory or motor preservation below the level of injury) spinal cord injury and spinal shock (absence of bulbocavernosus reflex) is determined following these evaluations. It should be appreciated that a complete clinical assessment, even in an awake cooperative patient, has a 79% to 93% sensitivity for injuries.10 Nonetheless, it would appear that most unstable spinal injuries will be suspected following a thorough clinical examination in an alert patient.10 
Table 44-2
Muscle Group Strength Should Be Graded From 0 (Absent) to 5 (Normal)
Motor Grade Examination Criteria
5 Able to resist full force resistance
4 Examiner able to overcome strength
3 Can overcome gravity, no resistance
2 Can move without gravity
1 Visible contraction
0 No contraction
X
Table 44-3
Classification of Spinal Cord Injuries According to Level of Impairment
Grade Motor Scorea Sensory Deficita
A 0/5 Complete
B 0/5 Incomplete
C <3/5 Incomplete
D >3/5 Incomplete
E 5/5 None
X

Imaging and Other Diagnostic Studies for Cervical Spine Fractures and Dislocations

Initial Imaging Protocol

In previous years, there was considerable debate regarding the use of plain radiographs or computed tomographic (CT) scans as screening tools. The advent of helical, multidetector CT equipment in most level I trauma centers, enabling rapid collection of reformatted CT scans for the head, neck, chest abdomen, and pelvis at the same time, has largely obviated the use of radiographs for screening. The use of CT scans as a screening modality for cervical spine trauma is now considered more cost-effective121 as well as more sensitive when compared with plain radiographs.165 In the trauma setting, radiographs often fail to capture the occipitocervical and cervicothoracic junctions.121 Occipital condylar fractures,16 occipitocervical dislocations, and upper cervical injuries25 are often underappreciated on radiographs. 
Radiographs may be used for screening patients who present to the emergency room with isolated cervical injuries from low-energy mechanisms or those who are treated at nontrauma centers. A lateral radiograph can be used in polytrauma patients presenting in extremis. In this setting, a lateral radiograph can provide sufficient information on the status of the osseoarticular structures of the cervical spine to facilitate a decision regarding emergent transport to the operating room.10,120 
The necessity for plain film imaging may be informed by the NEXUS low-risk criteria or the Canadian C-spine rules.10,224,225 NEXUS criteria would recommend against screening plain film images in an awake, alert patient without evidence of intoxication or other injury, no history of cervical spine tenderness or any tenderness on examination, and no neurologic signs or symptoms.10,225 The Canadian C-spine rule follows an algorithm that includes determination of age, mechanism of injury, neurologic signs, patient presentation, physical examination, and range of motion of the cervical spine.224,225 In a comparison between the NEXUS criteria and the Canadian C-spine rules, Stiell et al.225 reported that the Canadian C-spine rules were more sensitive and specific for injury. A prospective investigation regarding implementation of the Canadian C-spine rules at 12 trauma centers documented their safety and effectiveness, maintaining that no fractures were missed and no adverse outcomes reported.224 Moreover, prospective implementation of the rules resulted in a 13% reduction in cervical spine imaging, diminishing unnecessary radiation exposure, and increasing cost-effectiveness.224 
In the last decade, as magnetic resonance imaging (MRI) has become more readily available, controversy has arisen regarding the optimal means of determining the absence of cervical spine injury, particularly in the obtunded patient. Proponents of CT evaluation alone maintain that its high sensitivity and ability to clearly evaluate the osseous structures eliminates the need for further evaluation if the study is negative.10,62,121 Others, however, claim that MRI is the most sensitive modality to evaluate the cervical spine and will detect discoligamentous injuries that would otherwise be missed by CT scanning alone.172,210,220 For example, in a meta-analysis performed by Schoenfeld et al.210 regarding the use of MRI and CT versus CT alone for the evaluation of occult cervical spine injuries, MRI was found to identify abnormalities altering treatment in 6% of cases. The pooled sensitivity of MRI for detecting clinically significant cervical injury was 100%, with a 94% pooled specificity. In light of such findings, some authors have advocated a “rule of three” with respect to evaluation of the cervical spine, requiring that two out of three components (reliable physical examination in a cooperative patient, negative computed tomography, and/or negative MRI) be present to definitively declare a patient free of injury.220 

Injury Detection

Imaging studies must be systematically examined to minimize the risk of missing injuries. Ideally, radiographic evaluations of the cervical spine should be reviewed by a number of different practitioners independently to maximize the detection of occult injury.220 The assessment of cervical spine images should begin at the occipitocervical junction and proceed distally. For determination of occipitocervical dislocation, the Power’s ratio (Fig. 44-1) or “Harris’ rule of 12” (Fig. 44-2) can be used.37 The “Harris rule” involves the measurement of the Basion-Axis Interval and the Basion-Dens Interval, both of which should measure less than 12 mm if the occipitocervical articulation is intact.37,198 The “Harris rule” was initially described using plain radiograph imaging; however, a reevaluation relying on CT studies recommended that the threshold for the Basion-Dens Interval be revised to 8.5 mm.198 A consensus statement from the Spine Trauma Study Group recommended the use of the “Harris rule” over the Power’s ratio because of clinical utility.37 The occipital condyles should be well located within the superior articular processes of C1. Asymmetric widening or rotation suggests dislocation. Fractures of the occipital condyles are difficult to identify on plain radiographs, and CT evaluation, particularly sagittal and coronal reformats, is more useful for detection. 
Figure 44-1
 
The Power ratio is calculated by dividing the distance between the basion and the posterior C1 arch by the distance between the opisthion and the anterior C1 arch. A ratio greater than 1 is suggestive of an atlantooccipital dislocation.
The Power ratio is calculated by dividing the distance between the basion and the posterior C1 arch by the distance between the opisthion and the anterior C1 arch. A ratio greater than 1 is suggestive of an atlantooccipital dislocation.
View Original | Slide (.ppt)
Figure 44-1
The Power ratio is calculated by dividing the distance between the basion and the posterior C1 arch by the distance between the opisthion and the anterior C1 arch. A ratio greater than 1 is suggestive of an atlantooccipital dislocation.
The Power ratio is calculated by dividing the distance between the basion and the posterior C1 arch by the distance between the opisthion and the anterior C1 arch. A ratio greater than 1 is suggestive of an atlantooccipital dislocation.
View Original | Slide (.ppt)
X
Figure 44-2
 
Harris measurements, also known as the “rule of 12,” include the BAI (Basion-Axis Interval) and the BDI (Basion-Dens Interval). The BAI is the measured distance between the basion and a perpendicular line drawn in relation to the posterior vertebral body tangent line of C2. The BDI is the measured distance between the basion and the tip of dens. Both distances should normally be less than 12 mm.
Harris measurements, also known as the “rule of 12,” include the BAI (Basion-Axis Interval) and the BDI (Basion-Dens Interval). The BAI is the measured distance between the basion and a perpendicular line drawn in relation to the posterior vertebral body tangent line of C2. The BDI is the measured distance between the basion and the tip of dens. Both distances should normally be less than 12 mm.
View Original | Slide (.ppt)
Figure 44-2
Harris measurements, also known as the “rule of 12,” include the BAI (Basion-Axis Interval) and the BDI (Basion-Dens Interval). The BAI is the measured distance between the basion and a perpendicular line drawn in relation to the posterior vertebral body tangent line of C2. The BDI is the measured distance between the basion and the tip of dens. Both distances should normally be less than 12 mm.
Harris measurements, also known as the “rule of 12,” include the BAI (Basion-Axis Interval) and the BDI (Basion-Dens Interval). The BAI is the measured distance between the basion and a perpendicular line drawn in relation to the posterior vertebral body tangent line of C2. The BDI is the measured distance between the basion and the tip of dens. Both distances should normally be less than 12 mm.
View Original | Slide (.ppt)
X
In the atlantoaxial region, the atlanto-dens interval (ADI) and posterior atlanto-dens interval (PADI) must be assessed (Fig. 44-3). The normal ADI is less than 3 mm in adult patients and widening indicates disruption of the transverse ligament. This is often critical in predicting stability and the need for surgical intervention in C1 burst (Jefferson-type) fractures. The PADI is representative of the anteroposterior (AP) diameter of the spinal canal at C1. A PADI measuring less than 13 mm is suggestive of significant spinal canal compromise. Plain radiographs may assist in the diagnosis of odontoid process fractures or pars interarticularis fractures of C2. Odontoid fractures may be more subtle, however, and CT scanning can be helpful in identifying minimally displaced fractures. Attention should be paid to the cortical border of the odontoid and any areas of disruption noted. Bono et al.33 reported that intrarater reliability was high for diagnosing both odontoid and pars interarticularis fractures of C2. Among all measurements, the PADI was the most reproducible. For C2 pars fractures, the endplate method of angulation was more reproducible than the posterior vertebral body tangent.33 Importantly, some individuals manifest a “scar” in the area of the C1–C2 disc anlage that is obliterated during embryologic development to form the odontoid process. This normal variant should not be mistaken for a minimally displaced fracture. 
Figure 44-3
 
The atlanto-dens interval is measured from the posterior surface of the anterior CI ring to the anterior surface of the odontoid process (dens). The posterior atlanto-dens interval is measured from the posterior surface of the odontoid process to the anterior portion of the posterior CI ring.
The atlanto-dens interval is measured from the posterior surface of the anterior CI ring to the anterior surface of the odontoid process (dens). The posterior atlanto-dens interval is measured from the posterior surface of the odontoid process to the anterior portion of the posterior CI ring.
View Original | Slide (.ppt)
Figure 44-3
The atlanto-dens interval is measured from the posterior surface of the anterior CI ring to the anterior surface of the odontoid process (dens). The posterior atlanto-dens interval is measured from the posterior surface of the odontoid process to the anterior portion of the posterior CI ring.
The atlanto-dens interval is measured from the posterior surface of the anterior CI ring to the anterior surface of the odontoid process (dens). The posterior atlanto-dens interval is measured from the posterior surface of the odontoid process to the anterior portion of the posterior CI ring.
View Original | Slide (.ppt)
X
In the subaxial cervical spine, plain radiographs or CT scans can be used to screen for injuries. It may be difficult to visualize the cervicothoracic junction on plain radiographs, and injury cannot be definitively ruled out until this region is visualized. Weighted, or manual, traction on a patient’s arms may enhance plain radiographic evaluation of the cervicothoracic junction but such maneuvers cannot be employed in every trauma patient, particularly those with upper extremity injuries, shoulder dislocation, or scapulothoracic dissociation. A swimmer’s view can enhance the clarity of radiographs involving the cervicothoracic junction by eliminating overlapping shadows of the deltoid and glenohumeral joint. However, these views may also be impractical in the trauma setting and point toward the increased utility of CT scans, particularly with the added advantage of sagittal and coronal reformatting. 
A plain radiograph series of the subaxial cervical region must include an AP view, a lateral image that visualizes the cervicothoracic junction and possibly oblique images. The AP image should be scrutinized to determine malalignment of the spinous processes and interspinous process distances. If the patient is looking straight ahead, all spinous processes should be aligned. Rotation of the spinous processes may be a subtle finding, suggesting unilateral facet dislocation, facet fracture, or displaced pedicle fracture.14 Widening of the interspinous process distances indicates posterior ligamentous disruption. 
A systematic review of the lateral cervical spine radiograph begins with an assessment of the anatomic lines of the cervical spine: the anterior vertebral body line, the posterior vertebral body line, the spinolaminar line, and the interspinous line (Fig. 44-4). The spinolaminar line has been cited as being the most useful, given the fact that it is generally unaffected by the presence of degenerative changes and osteophytes. Disruption of the spinolaminar line may indicate facet fracture, subluxation, or dislocation, whereas an interrupted interspinous line suggests ligamentous injury. On a true lateral image, the facet joints will appear as stacked parallelograms. Any alteration of this configuration should be noted and further assessment performed to investigate the possibility of facet dislocation or subluxation. 
Figure 44-4
Radiographic lines, landmarks and measurements using a lateral cervical spine radiograph.
 
The spinolaminar line (A), posterior vertebral body line (B) and the anterior vertebral body line (C) are normally unbroken. On a perfect lateral view the facet joints should appear as stacked parallelograms (D). The prevertebral soft tissue shadow is measured at the level of C2 (E) and C6 (F) vertebral bodies. Greater than 6 mm of soft tissue shadow at C2 and 22 mm at C6 are strongly suggestive of an underlying spinal injury.
The spinolaminar line (A), posterior vertebral body line (B) and the anterior vertebral body line (C) are normally unbroken. On a perfect lateral view the facet joints should appear as stacked parallelograms (D). The prevertebral soft tissue shadow is measured at the level of C2 (E) and C6 (F) vertebral bodies. Greater than 6 mm of soft tissue shadow at C2 and 22 mm at C6 are strongly suggestive of an underlying spinal injury.
View Original | Slide (.ppt)
Figure 44-4
Radiographic lines, landmarks and measurements using a lateral cervical spine radiograph.
The spinolaminar line (A), posterior vertebral body line (B) and the anterior vertebral body line (C) are normally unbroken. On a perfect lateral view the facet joints should appear as stacked parallelograms (D). The prevertebral soft tissue shadow is measured at the level of C2 (E) and C6 (F) vertebral bodies. Greater than 6 mm of soft tissue shadow at C2 and 22 mm at C6 are strongly suggestive of an underlying spinal injury.
The spinolaminar line (A), posterior vertebral body line (B) and the anterior vertebral body line (C) are normally unbroken. On a perfect lateral view the facet joints should appear as stacked parallelograms (D). The prevertebral soft tissue shadow is measured at the level of C2 (E) and C6 (F) vertebral bodies. Greater than 6 mm of soft tissue shadow at C2 and 22 mm at C6 are strongly suggestive of an underlying spinal injury.
View Original | Slide (.ppt)
X
More occult injuries may be suspected because of increased prevertebral swelling in the soft tissues on a lateral radiograph (Fig. 44-4). If the soft-tissue shadow thickness anterior to the vertebral bodies measures more than 6 mm at the level of C2 or greater than 22 mm at the level of C6, then prevertebral swelling is present.163,231 It should be emphasized, however, that the sensitivity of this radiographic parameter has been found to be only 65%.126 
While flexion–extension radiographs were utilized extensively in the past, they have a very limited role in the contemporary evaluation of acute cervical spine trauma. A high incidence of false negatives has been noted in awake and alert patients, and obtunded individuals may be at risk of neurologic injury.10 Anderson et al.10 recommended against their use in obtunded patients and advocated that they be used only in the subacute setting. 

Imaging of Cervical Spine Fractures and Dislocations

Radiographs

In the subacute trauma setting, a complete radiographic series of the cervical spine should include a minimum of AP, lateral, and open-mouth odontoid views, with oblique images obtained as necessary. Injuries identified on initial screening studies can be investigated further by radiographs, and some parameters are useful in predicting stability and informing treatment. An example is the evaluation of C1 Jefferson burst fractures, where stability, as indicated by the integrity of the transverse ligament, is determined by displacement of the lateral masses of C1 on an open-mouth odontoid view. If the combined lateral overhang of the C1 lateral masses relative to those of C2 exceeds 6.9 mm (rule of Spence), a disrupted transverse ligament is inferred.37,93,222 As the 6.9-mm value was derived from direct anatomic measurements, it has been suggested that one magnification taking into account a measurement of 8.1 mm may be more appropriate.37 
At the C2 level, displacement and angulation of odontoid fractures are thought to influence the risk of nonunion and direct the need for surgical intervention. The Spine Trauma Study Group recommends that displacement of odontoid fractures be measured between two tangents drawn along the anterior cortex of the odontoid and C2 vertebral body, respectively (Fig. 44-5A).37 Angulation is determined by the angle created by the intersection of extrapolated lines drawn along the posterior cortex of the odontoid and the C2 vertebral body (Fig. 44-5B).37 For pars interarticularis fractures, the so-called hangman’s fracture, angulation may be assessed by the endplate method or posterior tangent technique. The endplate method uses the angle created by lines extrapolated from the inferior endplates of C2 and C3 (Fig. 44-6), whereas the posterior tangent technique utilizes lines extrapolated from the C2 and C3 posterior vertebral bodies (Fig. 44-7).37 Researchers from the Spine Trauma Study Group found that the endplate method of determining angulation was most reproducible.33 
Figure 44-5
 
A: Recommended measurement technique of odontoid displacement. B: Recommended measurement technique of odontoid angulation.
A: Recommended measurement technique of odontoid displacement. B: Recommended measurement technique of odontoid angulation.
View Original | Slide (.ppt)
A: Recommended measurement technique of odontoid displacement. B: Recommended measurement technique of odontoid angulation.
View Original | Slide (.ppt)
Figure 44-5
A: Recommended measurement technique of odontoid displacement. B: Recommended measurement technique of odontoid angulation.
A: Recommended measurement technique of odontoid displacement. B: Recommended measurement technique of odontoid angulation.
View Original | Slide (.ppt)
A: Recommended measurement technique of odontoid displacement. B: Recommended measurement technique of odontoid angulation.
View Original | Slide (.ppt)
X
Rockwood-ch044-image006.png
View Original | Slide (.ppt)
Figure 44-6
Endplate method of measuring C2–C3 angulation.
Rockwood-ch044-image006.png
View Original | Slide (.ppt)
X
Figure 44-7
Posterior vertebral body tangent line method for C2–C3 angulation measurement.
Rockwood-ch044-image007.png
View Original | Slide (.ppt)
X
For subaxial cervical evaluation, the lateral image is the most frequently utilized radiographic study. Comminution of fracture fragments should be appreciated if present and primary fracture lines outlined. Segmental kyphosis can be determined using an endplate (Cobb) technique or posterior vertebral body tangent similar to that described for hangman’s fractures (Figs. 44-8 and 44-9).35,36 In this setting as well, the endplate method has been found to be superior to vertebral body tangents.35 Kyphosis exceeding 11 degrees using the endplate method may indicate compromise of the posterior ligamentous complex (PLC) and instability.257 Subaxial cervical translation is assessed by determining the distance between extrapolated lines extending from the posterior vertebral bodies (Fig. 44-10).36 This measurement was found to be the most reproducible in the subaxial cervical spine on both plain film and CT scan.35 White and Panjabi257 advised that translation greater than 3.5 mm was suggestive of mechanical instability. Although less frequently encountered, lateral translation may be measured on the AP image by drawing vertical lines along the lateral masses at adjacent levels. 
Figure 44-8
The Cobb method of measuring cervical kyphosis.
 
A line is drawn along the superior endplate of the superior adjacent uninjured vertebrae; a second line is drawn along the inferior endplate of the inferior adjacent uninjured vertebrae. The angle subtended between the two is then measured.
A line is drawn along the superior endplate of the superior adjacent uninjured vertebrae; a second line is drawn along the inferior endplate of the inferior adjacent uninjured vertebrae. The angle subtended between the two is then measured.
View Original | Slide (.ppt)
Figure 44-8
The Cobb method of measuring cervical kyphosis.
A line is drawn along the superior endplate of the superior adjacent uninjured vertebrae; a second line is drawn along the inferior endplate of the inferior adjacent uninjured vertebrae. The angle subtended between the two is then measured.
A line is drawn along the superior endplate of the superior adjacent uninjured vertebrae; a second line is drawn along the inferior endplate of the inferior adjacent uninjured vertebrae. The angle subtended between the two is then measured.
View Original | Slide (.ppt)
X
Figure 44-9
The posterior vertebral body tangent method of measuring cervical kyphosis.
 
A line is drawn along the posterior aspect of the adjacent vertebral bodies. The angle subtended between the two is then measured.
A line is drawn along the posterior aspect of the adjacent vertebral bodies. The angle subtended between the two is then measured.
View Original | Slide (.ppt)
Figure 44-9
The posterior vertebral body tangent method of measuring cervical kyphosis.
A line is drawn along the posterior aspect of the adjacent vertebral bodies. The angle subtended between the two is then measured.
A line is drawn along the posterior aspect of the adjacent vertebral bodies. The angle subtended between the two is then measured.
View Original | Slide (.ppt)
X
Figure 44-10
Sagittal translation is measured at the level of the inferior aspect of the superior vertebral body.
Rockwood-ch044-image010.png
View Original | Slide (.ppt)
X
Determination of vertebral body height loss is performed by measuring the percentage difference between anterior and posterior vertebral body heights at the injured level (Fig. 44-11) compared with an average measurement obtained from adjacent levels above and below.36 Plain radiographic analysis of vertebral body height loss has been shown to be moderately reliable.35 
Figure 44-11
Vertebral body height loss can be expressed as a percentage.
 
This is best assessed by measuring both anterior and posterior height of the injured and adjacent uninjured vertebral bodies.
This is best assessed by measuring both anterior and posterior height of the injured and adjacent uninjured vertebral bodies.
View Original | Slide (.ppt)
Figure 44-11
Vertebral body height loss can be expressed as a percentage.
This is best assessed by measuring both anterior and posterior height of the injured and adjacent uninjured vertebral bodies.
This is best assessed by measuring both anterior and posterior height of the injured and adjacent uninjured vertebral bodies.
View Original | Slide (.ppt)
X

Computed Tomography

CT scans are more sensitive than plain radiographs in identifying fractures and subtle osseoarticular abnormalities.10,120,145,165 Helical multidetector CT technology produces images with good anatomic detail and is now the screening modality of choice for cervical trauma at most level I centers.10,62,67,121 
It is highly advantageous to link axial and sagittal images such that two studies can be reviewed together with the spinal levels in approximation. If this is not possible, the vertebral bodies and pedicle of each cervical level should be labeled so that the location of fractures or articular injuries can be accurately defined. Vertebral bodies should be inspected to determine the presence of fracture lines, especially on the axial image that has a higher sensitivity for detecting sagittal split fractures than on the plain radiographs. If a fracture is present, the degree of comminution and retropulsion into the spinal canal will also be apparent. Facet, lamina, and pedicle fractures are notoriously difficult to identify on plain radiographs but may be more easily appreciated on axial CT studies. Spinous process fractures will also be easily visualized. 
Vertebral body translation and frank dislocation are also demonstrable on axial CT scans (Fig. 44-12). If a substantial amount of translation is present, as in bilateral facet dislocations, a “double-lumen” sign may be present on a single axial image.40 More subtle findings may be discerned by examining the facet joints at each cervical level. In a normal cervical spine, the inferior articular process from the level above lies dorsal to the superior articular process of the level below. The absence of opposed articular surfaces may result in an “empty facet sign.” In facet dislocations, the inferior articular process of the level above will be visualized anterior to the superior articular process of the caudal vertebrae. 
Figure 44-12
 
Frank dislocation is usually obvious on axial computed tomographic images, as in this case of a C6–C7 fracture dislocation. More subtle amounts of translation, however, can be easily missed using axial computed tomographic images alone.
Frank dislocation is usually obvious on axial computed tomographic images, as in this case of a C6–C7 fracture dislocation. More subtle amounts of translation, however, can be easily missed using axial computed tomographic images alone.
View Original | Slide (.ppt)
Figure 44-12
Frank dislocation is usually obvious on axial computed tomographic images, as in this case of a C6–C7 fracture dislocation. More subtle amounts of translation, however, can be easily missed using axial computed tomographic images alone.
Frank dislocation is usually obvious on axial computed tomographic images, as in this case of a C6–C7 fracture dislocation. More subtle amounts of translation, however, can be easily missed using axial computed tomographic images alone.
View Original | Slide (.ppt)
X
Coronal and sagittal reconstructions facilitate the more complete visualization of the three-dimensional nature of spinal injuries. Both coronal and sagittal reconstructions can be used to evaluate widening across the occipitoatlantal joint and fractures of the occipital condyles. Paramedian sagittal cuts through the facet joints may help appreciate dislocations, subluxations, and estimations of fracture fragment size (Fig. 44-13). Retropulsion of fracture fragments into the canal, and resultant compromise, can best be estimated on a midsagittal CT scan. 
Figure 44-13
Sagittal computed tomographic reconstructions are useful for assessing the facet joints.
 
In this case, a C5–C6 unilateral facet dislocation can be appreciated. A small articular process fracture fragment can also be noted (arrow).
In this case, a C5–C6 unilateral facet dislocation can be appreciated. A small articular process fracture fragment can also be noted (arrow).
View Original | Slide (.ppt)
Figure 44-13
Sagittal computed tomographic reconstructions are useful for assessing the facet joints.
In this case, a C5–C6 unilateral facet dislocation can be appreciated. A small articular process fracture fragment can also be noted (arrow).
In this case, a C5–C6 unilateral facet dislocation can be appreciated. A small articular process fracture fragment can also be noted (arrow).
View Original | Slide (.ppt)
X

Magnetic Resonance Imaging

The precise role of MRI in the evaluation of patients with cervical spine trauma, as well as the timing of studies, remains to be conclusively defined.10,62,166,210,220 At present, MRI is known to be superior to computed tomography in terms of visualizing cervical soft-tissue structures, including the spinal cord, cervical nerve roots, intervertebral discs, and posterior ligamentous complex (PLC).172 MRI is also useful in detecting subtle compressive injuries, undisplaced fractures of the vertebral bodies (via the presence of osseous edema), epidural hematomas, and vertebral artery injury. Despite advances in the different types of imaging studies (e.g., T1-weighted, T2-weighted, Short-Tau Inversion Recovery), the osseous anatomy is still more clearly depicted on computed tomography, and MRI cannot be utilized as a stand-alone imaging modality for the detection of all injuries in spine trauma.10 It should be recognized, however, that MRI has been criticized by some as being overly sensitive, with a high incidence of clinically insignificant injury detection that does not alter treatment (e.g., nonspecific fluid signal in the posterior soft tissues without evidence of other spinal injury).10,210,220 
In the authors’ practice, if there are no contraindications, an MRI scan is obtained in cases of cervical spine trauma when any of the following criteria are met: (1) the patient presents with a neurologic deficit, (2) the integrity of the PLC is unclear and injury to this structure would have a direct influence on treatment, such as determining the need for surgery, and (3) the patient presents with a facet dislocation where there is concern regarding disc herniation into the spinal canal that may prevent safe reduction and cause difficulty in deciding on the correct approach for surgical intervention. 
T2-weighted images provide the best initial MRI review of cervical trauma. These studies have a so-called “myelography effect,” in that the cerebrospinal fluid (CSF) is bright and the discoligamentous structures are relatively dark or isointense. T2-weighted images may demonstrate increased signal within the disc, facet capsules, or posterior interspinous process region, indicative of edema or frank disruption. The anatomical outlines of the anterior longitudinal ligament (ALL), posterior longitudinal ligament (PLL) or tectorial membrane (as the PLL is renamed at the occipitocervical junction), and ligamentum flavum can all be appreciated on T2-weighted MRI (Fig. 44-14). On axial images at the level of C1, the integrity of the transverse and alar ligaments may also be assessed (Fig. 44-15). In some individuals, the ALL is not contiguous throughout the cervical spine.203 Therefore, discontinuity in the absence of increased T2 uptake may not necessarily be consistent with acute injury. Short-Tau Inversion Recovery sequences can be used as adjunct studies, with an enhanced capacity to detect soft-tissue and osseous edema. Image detail and anatomy are less well appreciated, however. 
Figure 44-14
Magnetic resonance imaging can be used to assess several important soft-tissue structures in the cervical spine.
 
In this sagittal T2-weighted image of a patient with a C6 vertebral body fracture, the small arrows are pointing to the posterior longitudinal ligament, which is disrupted along the posteroinferior aspect of the fractured level (lower small arrow). The large black arrow indicates the ligamentum flavum at an uninjured level. The large white arrow indicates an area of the ligamentum flavum that has been disrupted.
In this sagittal T2-weighted image of a patient with a C6 vertebral body fracture, the small arrows are pointing to the posterior longitudinal ligament, which is disrupted along the posteroinferior aspect of the fractured level (lower small arrow). The large black arrow indicates the ligamentum flavum at an uninjured level. The large white arrow indicates an area of the ligamentum flavum that has been disrupted.
View Original | Slide (.ppt)
Figure 44-14
Magnetic resonance imaging can be used to assess several important soft-tissue structures in the cervical spine.
In this sagittal T2-weighted image of a patient with a C6 vertebral body fracture, the small arrows are pointing to the posterior longitudinal ligament, which is disrupted along the posteroinferior aspect of the fractured level (lower small arrow). The large black arrow indicates the ligamentum flavum at an uninjured level. The large white arrow indicates an area of the ligamentum flavum that has been disrupted.
In this sagittal T2-weighted image of a patient with a C6 vertebral body fracture, the small arrows are pointing to the posterior longitudinal ligament, which is disrupted along the posteroinferior aspect of the fractured level (lower small arrow). The large black arrow indicates the ligamentum flavum at an uninjured level. The large white arrow indicates an area of the ligamentum flavum that has been disrupted.
View Original | Slide (.ppt)
X
Figure 44-15
 
Axial T2-weighted magnetic resonance image through the C1 ring, showing an intact transverse ligament (arrowheads) spanning the C1 lateral masses over the posterior surface of the odontoid process (O).
Axial T2-weighted magnetic resonance image through the C1 ring, showing an intact transverse ligament (arrowheads) spanning the C1 lateral masses over the posterior surface of the odontoid process (O).
View Original | Slide (.ppt)
Figure 44-15
Axial T2-weighted magnetic resonance image through the C1 ring, showing an intact transverse ligament (arrowheads) spanning the C1 lateral masses over the posterior surface of the odontoid process (O).
Axial T2-weighted magnetic resonance image through the C1 ring, showing an intact transverse ligament (arrowheads) spanning the C1 lateral masses over the posterior surface of the odontoid process (O).
View Original | Slide (.ppt)
X
Magnetic resonance arteriography can be employed in the assessment of vertebral artery injury and patency. Such studies may be indicated in the setting of severe facet dislocations or fractures that extend into the transverse foramen. There are no firm recommendations or algorithms that highlight when magnetic resonance arteriography is required, and practice differs substantially between centers.202 As unilateral occlusions are often asymptomatic, and recanalization may occur with time, anticoagulant therapy is not always recommended. However, knowledge of the presence of a compromised vertebral artery may be useful if posterior instrumentation is planned as the use of lateral mass screws may put the only patent artery at risk. 

Outcome Scores and Instruments for Cervical Spine Fractures and Dislocations

Currently, no outcome instrument or score exists that is specific for spinal trauma in general and cervical spine injuries in particular.209 In the absence of a singular standardized outcome measure for spinal trauma, Schoenfeld and Bono209 recommended that researchers utilize a combination of scores, including a generic health survey (e.g., SF-36), a measure of spine-specific function (e.g., Roland-Morris Disability Questionnaire, Neck Disability Index), a pain scale, and a radiographic indicator of successful fusion or fracture healing.209 Studies investigating Health-Related Quality of Life should employ specific surveys such as the SF-6D or EQ-5D.209 
A challenge exists, however, in that none of the current instruments were developed for, or validated in, populations presenting with spinal injuries. Furthermore, the goals and value of intervention differ substantially between elective spine surgery and surgical treatment of trauma, and the current studies may not be able to account for this.209 Nonetheless, the American Academy of Orthopaedic Surgeons/North American Spine Society (AAOS/NASS) questionnaire79 and Neck Disability Index261 have both been successfully applied, although not validated, in populations with cervical spine trauma. The Roland–Morris questionnaire may be more applicable to the thoracic or lumbar regions,209 whereas surveys specific to fracture pattern (e.g., European Vertebral Osteoporosis Study (EVOS) or Quality of Life Questionnaire of the European Foundation for Osteoporosis (QUALEFFO) for compression fractures) likely cannot be adapted to the cervical spine at all. 

Pathoanatomy and Applied Anatomy of the Cervical Spine

The upper cervical spine consists of the atlas (C1), axis (C2), and the skull base (C0) including the occiput. The anatomy at each level is unique and differs from the subaxial cervical region. The subaxial cervical spine includes the C3 to C7 vertebral segments, which maintain a relatively uniform anatomical configuration analogous to the thoracic and lumbar spine. 

Upper Cervical Spine (Occiput to C2)

Occipitocervical Region

The occipital bone is the diploic posteroinferior aspect of the cranium that cradles the cerebellum and the brain stem. At its anterior and inferior aspect, it forms the posterior part of the foramen magnum, which emits the spinal cord into the spinal canal. The occiput has several bony structures that are useful surgical landmarks. At its topographical center, the external occipital protuberance (inion) is a dense uprising that marks the thickest portion of the bone (Fig. 44-16). The superior nuchal line is a ridge that extends medial and lateral from the inion. The inferior nuchal line is a similar condensation running parallel and below its superior counterpart. Although not a useful surgical landmark, the lambdoidal suture denotes the borders of the occipital bone at its fused junctions with the temporal and parietal bones. The occiput curves sharply anterior from the superior nuchal line to the foramen magnum. This feature makes accurate contouring of implants to match the skeletal geometry challenging. The occiput interfaces with the cervical spine through bilateral articular condyles on either side of the foramen magnum. 
Figure 44-16
 
Sagittal computed tomographic reconstruction through the occiput of a patient with an odontoid fracture demonstrating that the inion (external occipital protuberance) is located at the thickest portion of the bone (double-arrowed line).
Sagittal computed tomographic reconstruction through the occiput of a patient with an odontoid fracture demonstrating that the inion (external occipital protuberance) is located at the thickest portion of the bone (double-arrowed line).
View Original | Slide (.ppt)
Figure 44-16
Sagittal computed tomographic reconstruction through the occiput of a patient with an odontoid fracture demonstrating that the inion (external occipital protuberance) is located at the thickest portion of the bone (double-arrowed line).
Sagittal computed tomographic reconstruction through the occiput of a patient with an odontoid fracture demonstrating that the inion (external occipital protuberance) is located at the thickest portion of the bone (double-arrowed line).
View Original | Slide (.ppt)
X
The occipitocervical region is stabilized by numerous ligaments. A durable capsule stabilizes the articulation of the occipital condyles to the atlas. A broadsheet of fibrous tissue extends from the posterior border of the foramen magnum to the superior surface of the C1 ring. This is the tectorial membrane, which is analogous to the PLL in the lower cervical spine. A loose and flexible sheet of fibrous tissue spans between the lower occiput and the posterior C1 ring. This is called the posterior atlantooccipital membrane and is analogous to the ligamentum flavum at other levels. Entering this membrane approximately 1.5 cm from the posterior midline is the vertebral artery (Fig. 44-17). The artery emerges lateral and posterior to the membrane from the transverse foramen of the atlas. This vessel can be injured with extensive exposure of the posterior C1 ring. The ligamentum nucha is a thick condensation of supraspinous fibrous bands. This structure overlays the spinous processes of the cervical vertebrae and extends from the inion to C7. 
Figure 44-17
 
During exposure of the posterior C1 arch, dissection should not extend beyond 1.5 cm in the posterior midline, or 1 cm along the superior border, in order to avoid injury to the vertebral artery.
During exposure of the posterior C1 arch, dissection should not extend beyond 1.5 cm in the posterior midline, or 1 cm along the superior border, in order to avoid injury to the vertebral artery.
View Original | Slide (.ppt)
Figure 44-17
During exposure of the posterior C1 arch, dissection should not extend beyond 1.5 cm in the posterior midline, or 1 cm along the superior border, in order to avoid injury to the vertebral artery.
During exposure of the posterior C1 arch, dissection should not extend beyond 1.5 cm in the posterior midline, or 1 cm along the superior border, in order to avoid injury to the vertebral artery.
View Original | Slide (.ppt)
X
There are few muscles that directly span the occiput and the atlas. The superior obliquus capitis muscle runs from the lateral aspect of the superior nuchal line to the transverse process of C1. Medially, the rectus capitis posterior minor attaches to the superior nuchal line and the C1 spinous process. The rectus capitis posterior major muscle extends from the superior nuchal line to the spinous process of C2. Spanning from the mastoid process of the skull, the longissimus capitis blends with the deep muscles of the upper thoracic paraspinal region. 

Atlantoaxial Region

The upper cervical vertebrae are unique compared with the subaxial spine (Fig. 44-18). The atlas has large broad-based articular processes to interface with the occipital condyles superiorly and the axis inferiorly. An articular surface on the posterior aspect of the anterior arch faces the odontoid process of the axis. The posterior ring of C1 is quite thin with no discrete spinous process. The axis articulates with C1 at three points: two broad bilateral superior articular surfaces and the odontoid process. Its morphology allows approximately 47 degrees of rotation (50% of axial rotation of the entire cervical spine), while limiting flexion/extension to 10 degrees. Virtually no lateral bending is permitted at the atlantoaxial articulation. The axis marks the transition between the upper and lower cervical spine. In light of this transition, the inferior articular processes of C2 are offset posteriorly. Because of this offset, the pars interarticularis sustains high shear forces with axial loading, predisposing it to the classic hangman’s fracture pattern. Again, a foramen in the transverse processes transmits the ascending vertebral artery. The cervical nerve roots exit through foramina formed by adjacent superior and inferior pedicle walls. The ligamentum flavum proper is first apparent at this level, extending from the inferior ring of C1 to the superior ring of C2. The flavum attaches more ventral (deep) on the C1 ring and more dorsal on the C2 ring. This is an important consideration when elevating this membrane from a posterior approach to expose the cervical laminae for decompression. 
Figure 44-18
Diagram of the subaxial cervical spine viewed from the front.
 
The bilateral uprisings, known as the uncinate processes, create a cup-in-saucer formation of the intervertebral disc space.
The bilateral uprisings, known as the uncinate processes, create a cup-in-saucer formation of the intervertebral disc space.
View Original | Slide (.ppt)
Figure 44-18
Diagram of the subaxial cervical spine viewed from the front.
The bilateral uprisings, known as the uncinate processes, create a cup-in-saucer formation of the intervertebral disc space.
The bilateral uprisings, known as the uncinate processes, create a cup-in-saucer formation of the intervertebral disc space.
View Original | Slide (.ppt)
X
Several muscles connect the atlas and the axis. As in other spinal regions, small bilateral interspinalis muscles span between spinous processes. The inferior obliquus capitis extends from the transverse process of C1 laterally to the spinous process of C2 medially. It is at the inferior border of this muscle that the greater occipital nerve exits posteriorly, traveling cranial and medial to lie superficial to the rectus capitis posterior minor and obliquus capitis superior muscles. Finally, it exits the trapezius near the midline over the inion and can be injured with lateral dissection at this level. Nerve injury can lead to anesthesia of the posterior scalp, which may be bothersome to some patients. 

Lower Cervical Spine (C3–C7)

Anterior Elements

The vertebral body is an oblong structure, with a coronal diameter that is larger than its sagittal diameter. Distinct from the normally flat endplates of the thoracic and lumbar vertebrae, cervical endplates have a cup-in-saucer configuration. Viewed from the front (Fig. 44-18), bilateral projections called the “uncinate processes of Luschka” extend from the lateral aspects of the superior endplates. The uncinate processes articulate with rounded inferolateral borders of the suprajacent vertebral body. This articulation, called the “uncovertebral joint,” is a useful surgical anatomical landmark that signals proximity to the lateral extent of the vertebral body. Mechanically, it is believed to limit posterior translation of the cephalad vertebra.257 
The intervertebral disc is interposed between the endplates of adjacent vertebral bodies. The annulus fibrosis is intimately related to the ALL and the PLL. The longus colli muscles lie directly over and insert onto the anterolateral aspects of each cervical vertebrae. The sympathetic plexus lies on top of the lateral longus colli, placing it at risk with overly aggressive dissection or retraction, which can result in Horner’s syndrome. A series of fascial layers invest the anterior cervical structures and separate them from the viscera. The prevertebral fascia separates the cervical spine from the overlying esophagus. The pretracheal fascia communicates with the carotid sheath, whereas the deep cervical fascia is an extension of the layer enveloping the sternocleidomastoid muscle. 
Transverse processes project from the lateral aspects of the vertebral body. In contrast to their flat, solid analogues in the thoracic and lumbar spine, cervical transverse processes have a more complex anatomic shape. This is the result of their distinct embryologic development. The anterior portion (Fig. 44-19) of the transverse process is actually the remnant of a rudimentary costal process. While the costal processes form ribs in the thoracic spine, in the cervical region each costal process fuses with the true transverse process anlage to form the foramen transversarium that transmits the vertebral artery. At C6, there is a large accessory process in the area of the transverse foramen. This prominence, alternately called the “carotid process” or “Chassaignac’s tubercle,” can be palpated directly and is a useful landmark for identifying the C6 level for anterior surgical approaches. The vertebral artery ascends to the head through the C6 to C1 foramen transversaria. It enters the C7 transverse foramen in only 5% of the population.137 Fractures that enter or displace the transverse processes suggest possible traumatic injury, or occlusion, of the vertebral artery. 
Figure 44-19
The transverse process is made of two components.
 
The anterior portion is actually the remnant of a costal process (i.e., rudimentary rib). The posterior portion is the true developmental transverse process. Together, they form the transverse foramen, the conduit for the vertebral artery.
The anterior portion is actually the remnant of a costal process (i.e., rudimentary rib). The posterior portion is the true developmental transverse process. Together, they form the transverse foramen, the conduit for the vertebral artery.
View Original | Slide (.ppt)
Figure 44-19
The transverse process is made of two components.
The anterior portion is actually the remnant of a costal process (i.e., rudimentary rib). The posterior portion is the true developmental transverse process. Together, they form the transverse foramen, the conduit for the vertebral artery.
The anterior portion is actually the remnant of a costal process (i.e., rudimentary rib). The posterior portion is the true developmental transverse process. Together, they form the transverse foramen, the conduit for the vertebral artery.
View Original | Slide (.ppt)
X
In addition to housing the vertebral artery, the posterior aspect of the transverse process guides the cervical spinal nerves as they exit the spinal canal. The spinal nerves lie posterior to the vertebral artery. If the spine is viewed from the side, the spinal nerve appears to be cradled by the half-pipe configuration of the transverse process (Fig. 44-20), as it projects in an anteroinferior direction. 
Figure 44-20
Diagram of a side view of the cervical spine.
 
The transverse process forms a half-pipe configuration that cradles the exiting spinal nerve, while the overall alignment is normally lordotic.
The transverse process forms a half-pipe configuration that cradles the exiting spinal nerve, while the overall alignment is normally lordotic.
View Original | Slide (.ppt)
Figure 44-20
Diagram of a side view of the cervical spine.
The transverse process forms a half-pipe configuration that cradles the exiting spinal nerve, while the overall alignment is normally lordotic.
The transverse process forms a half-pipe configuration that cradles the exiting spinal nerve, while the overall alignment is normally lordotic.
View Original | Slide (.ppt)
X

Posterior Elements

The cervical pedicles project from the vertebral body in an orientation that runs posterolateral to anteromedial. The pedicles form the posteromedial border of the transverse foramina and the anterolateral aspect of the spinal canal. The internal morphology of the cervical pedicles, including the medial and lateral cortical thickness, can vary substantially on the basis of vertebral level and gender.80,184 Such characteristics render transpedicular screw insertion technically difficult, with a high potential for neurovascular injury. 
The facet joints, also called the “zygapophyseal articulations,” are highly mobile diarthrodial joints formed by the interaction of superior and inferior articular processes from adjacent vertebrae. These processes emanate from the posterior aspect of the pedicles and transverse processes (Fig. 44-20). The articular surfaces are angled approximately 45 degrees in relation to the transverse axis of each segment. There is minimal, if any coronal angulation. The pillar of bone between the superior and inferior articular processes is commonly referred to as the lateral mass. It is a useful site for posterior screw or wire stabilization of the cervical spine. 
The laminae arise from the posteromedial border of the lateral masses. The laminae project posteriorly, and toward the midline, to form bifid spinous processes between C2 and C6. An elastic yellow ligament, the ligamentum flavum, spans each interlaminar space and is noncontiguous in nature. Along with the ligamentum flavum, the strong interspinous and supraspinous ligaments (ligamentum nuchae) form the PLC. Disruption of these structures can result in mechanical instability. 

Spinal Canal and Canal Compromise

The spinal cord lies within the spinal canal. The borders of the canal at the levels of C2 to C7 are as follows: 
  1.  
    Anterior: vertebral body, intervertebral disc, PLL
  2.  
    Posterior: laminae, ligamentum flavum
  3.  
    Lateral: pedicles (anterolateral), medial aspect of the facet joints (posterolateral)
The spinal canal can be compromised after traumatic injury in several ways. Fracture fragments, most commonly retropulsed from the vertebral body, may impinge upon the canal and spinal cord. In the cervical region, the amount of canal compromise directly correlates to the risk of neurologic injury. Kang et al.138 reported that the mean space available for the cord in a series of patients with complete injury was approximately 10.5 mm. In contrast, the space available for the cord in patients with spinal injuries but no neurologic deficit was close to 17 mm. Those with incomplete spinal cord injury had a mean space available for the cord of 13 mm.138 
One of the most common etiologies of canal compromise following cervical trauma is translational malalignment, as occurs with facet joint dislocations (Fig. 44-21). In such situations, the osseous structures and neural arch may be intact. Nonetheless, their relative position results in canal compromise. The degree of canal compromise in this setting may be underestimated by axial CT scans, and additional information should be sought from sagittal and coronal reconstructions. Disc herniations and epidural hematoma can also occupy space within the canal, resulting in spinal cord compression. 
Figure 44-21
 
Spinal canal compromise in the cervical spine most commonly occurs from translational deformity, as depicted in the sagittal computed tomographic reconstruction of a patient with a unilateral facet dislocation. The normal anteroposterior dimension of the canal is noted above (A) and below (C) the injury. At the level of the translational deformity, the spinal canal is smaller (B).
Spinal canal compromise in the cervical spine most commonly occurs from translational deformity, as depicted in the sagittal computed tomographic reconstruction of a patient with a unilateral facet dislocation. The normal anteroposterior dimension of the canal is noted above (A) and below (C) the injury. At the level of the translational deformity, the spinal canal is smaller (B).
View Original | Slide (.ppt)
Figure 44-21
Spinal canal compromise in the cervical spine most commonly occurs from translational deformity, as depicted in the sagittal computed tomographic reconstruction of a patient with a unilateral facet dislocation. The normal anteroposterior dimension of the canal is noted above (A) and below (C) the injury. At the level of the translational deformity, the spinal canal is smaller (B).
Spinal canal compromise in the cervical spine most commonly occurs from translational deformity, as depicted in the sagittal computed tomographic reconstruction of a patient with a unilateral facet dislocation. The normal anteroposterior dimension of the canal is noted above (A) and below (C) the injury. At the level of the translational deformity, the spinal canal is smaller (B).
View Original | Slide (.ppt)
X
At the C1 level, the anterior border of the spinal canal is demarcated by the posterior aspect of the odontoid process, whereas the posterior border is the ventral surface of the posterior C1 ring. This is the only level in the spine where the borders of the spinal canal are defined by elements from two different vertebrae. 

Cervical Spinal Cord Anatomy

Injury to the cervical spinal cord can occur as a result of ischemia, compression, distraction, penetration, or a combination of these mechanisms. Knowledge of spinal cord and nerve root anatomy is useful in establishing the level and type of spinal cord injury. 
The externally visible portion of the spinal cord is composed of white matter covered by pia mater. The white color is derived from myelin, that sheaths the axons, being transmitted between the brain and the peripheral tissues. There are several afferent and efferent tracts that are embedded within the substance of the white matter (Fig. 44-22). The lateral spinothalamic tract is an afferent (ascending) tract located within the anterolateral aspect of the cord that transmits pain and temperature sensation. It is somatopically arranged, with the axons of more cephalad levels localized within the anteromedial aspect and those of the caudal levels localized to the posterolateral region. Nerve fibers transmitting pain and temperature decussate at the same level where they exit the spinal cord. Therefore, injury to the lateral spinothalamic tract results in pain and temperature loss on the contralateral side of the body. 
Figure 44-22
Cross section through the spinal cord.
 
There are distinct somatotopic patterns of innervation, which help explain the clinical presentation of various types of incomplete spinal cord injury.
There are distinct somatotopic patterns of innervation, which help explain the clinical presentation of various types of incomplete spinal cord injury.
View Original | Slide (.ppt)
Figure 44-22
Cross section through the spinal cord.
There are distinct somatotopic patterns of innervation, which help explain the clinical presentation of various types of incomplete spinal cord injury.
There are distinct somatotopic patterns of innervation, which help explain the clinical presentation of various types of incomplete spinal cord injury.
View Original | Slide (.ppt)
X
The lateral and ventral corticospinal tracts transmit efferent (descending/motor) fibers. They are also somatopically arranged, with more cephalad levels located in the interior, anteromedial substance of the cord. Motor nerve fibers decussate above the level of the foramen magnum so that injuries to these tracts within the cord result in ipsilateral loss of function. 
The dorsal columns comprise the fasciculus gracilis and fasciculus cuneatus (Fig. 44-22). These tracts transmit proprioception, vibratory sense, pressure, and tactile discrimination to the brain. The dorsal columns are also arranged somatopically. However, nerve fibers to the more cephalad levels are located within the lateral regions of the tract. These nerve fibers also decussate above the foramen magnum, before the spinal cord is formed. Similar to the corticospinal tracts, injury to the gracile and cuneate fasciculi result in ipsilateral deficits. 
Spinal cord gray matter consists of collections of nerve cell bodies. In a cross section of the spinal cord, the central gray matter maintains an H-shaped appearance that is divided into dorsal and anterior horns (Fig. 44-22). The dorsal horns contain sensory nerve cell bodies that transmit pain, temperature, and touch. The anterior horns contain motor nerve cell bodies. Gray matter is topographically arranged such that more cephalad innervations are derived from its central aspects. This arrangement is the physiologic explanation for the more prominent upper extremity involvement in patients with central cord syndrome. 
The blood supply of the cervical spinal cord is dependent on an anterior spinal artery, located in the midline, and two posterior spinal arteries. These structures are supplied by segmental arteries that arise from the vertebral arteries and enter the canal through the intervertebral foramina. The most consistent segmental vessel is located at the level of C5–C6. Apically, the basilar artery also anastomoses with the anterior spinal artery and can potentially supply collateral circulation to the level of C4. Although often depicted as such, the anterior and posterior spinal arteries may not be contiguous structures that run the entire length of the spinal cord. Rather, depending on individual variation, the anterior and posterior spinal arterial structures may be short longitudinal segments that are highly dependent on their segmental feeder vessels. This can explain why if the vascular supply is compromised by trauma, devastating neurologic injury may result even in the absence of severe canal compromise or significant osseoarticular injury. 

Treatment Options for Cervical Spine Fractures and Dislocations

The treatment of the patient with a cervical spine injury is directed by several important goals. The primary goal is maintenance, or restoration, of neurologic function. This may require decompression of the spinal cord and neural structures or reduction and realignment of facet dislocations or displaced fractures. The preservation of neurologic function is also predicated on the mechanical stability of the spine. The spine may be rendered unstable by the initial trauma mechanism or by surgical procedures, such as laminectomy or discectomy, required to decompress the neurologic elements. In most instances, stability is restored via surgical intervention and instrumentation of the spine, although closed means, such as halo-fixation have been employed effectively in the past.31,123,141 
Secondary goals of treatment include fracture healing, diminution of pain, mitigation of disability, and restoration of function. Even after complete spinal cord injury, surgical intervention and spinal fusion may be necessary to allow a patient to sit upright in a wheelchair, maintain forward gaze, and ameliorate long-term issues such as chronic pain or Charcot arthropathy of the spine. In patients with stable cervical fractures, in the absence of neurologic impairment, bracing and external orthoses have been employed successfully to potentiate healing. 

Nonoperative Management of Cervical Spine Fractures and Dislocations

Cervical Orthoses

Many cervical spine fractures can be managed nonoperatively. If the fracture is stable, treatment usually consists of immobilization in a cervical orthosis. Cervical orthotics tend to decrease rather than eliminate motion because of the fact that endpoint control is difficult in the cervical spine and substantial external pressures may put vital structures such as the trachea, esophagus, and carotid arteries at risk.3 In many instances, an external orthosis may serve only as a reminder to the patients to limit attempts at motion or to restrict their activity level. Most cervical orthotics use three-point pressure to restrict motion, generally making contact with the mandible and the occiput proximally, the clavicle and the sternal notch anteroinferiorly, and the T3 spinous process and scapular spines posteriorly. 
Soft cervical collars are solely employed for muscle sprains or strains and are utilized for comfort only. They provide no immobilization and have no role in the treatment of patients with acute injuries to the cervical spine. A variety of rigid cervical collars are currently available and provide differing degrees of immobilization depending on their design and material composition. Some of the more commonly encountered cervical collars in a clinical setting are the Miami-J, Philadelphia, and Aspen devices. The foam composition of the Philadelphia collar facilitates personal hygiene, whereas the Miami-J contains removable pads that, although washable, must be changed frequently. A number of biomechanical studies have suggested the superiority of one type of collar over another, although these findings have not been found to translate into clinical differences. Askins and Eismont15 maintained that the NecLoc device restricted flexion–extension, axial rotation, and lateral bending moments to a greater degree than the Miami-J, Philadelphia, Aspen, or Stiffneck orthoses. These authors also advised that the Miami-J was superior to the remaining devices. In a cadaver study, Richter et al.196 found that the Miami-J was capable of immobilizing the upper cervical spine as effectively as a cervicothoracic orthosis (CTO). Schneider et al.207 proposed that, in the treatment of a stable cervical fracture, any cervical orthosis could be used. In light of its superior comfort, and demonstrated biomechanical advantage over several other devices, many clinicians prefer to use the Miami-J collar in their clinical practice.3 
Several complications can occur with prolonged use of cervical orthoses. These include pressure ulcers in the areas of contact, particularly the occiput, angle of the mandible, and sternum. The incidence of skin complications has been reported to be as high as 38% in patients with severe closed head injuries treated with prolonged cervical immobilization.56 Use of cervical immobilization can also make swallowing difficult, increase the risk of aspiration, and increase intracranial pressure in patients with head injuries. Because of these associated risks, a premium has been placed on the expeditious exclusion of cervical spine injuries such that unnecessary protracted immobilization can be eliminated. 

Cervicothoracic Orthoses for Cervical Spine Fractures and Dislocations

CTOs consist of a cervical immobilization apparatus with a thoracic extension that immobilizes the cervicothoracic junction and distally to T5.3 CTOs are more effective in immobilizing the cervical spine than stand-alone cervical orthoses in all planes because they achieve better control of the head.3,136,207 Commonly available CTOs include the sterno-occipito-mandibular immobilizer, the Yale brace, Minerva brace, Lerman noninvasive halo (NIH), and pinless NIH.3,205 In a biomechanical study, Sharpe et al.219 demonstrated that 79% to 87% of sagittal motion, 75% to 77% of axial rotation, and 51% to 61% of lateral bending were restricted by the Minerva device. Agabegi et al.3 also endorsed the Minerva as a viable alternative to conventional halo fixation in compliant patients who would not take off, or tamper with, the device. Advantages over traditional halo-thoracic vests include the elimination of pin fixation with a consequent reduction in infection rates and reduced pressure ulcer formation.3,205 Pressure ulcers, however, can still occur with CTOs, and they also have been reported to exert high resting pressures on the chin and the occiput. 
Recently, Sawers et al.205 reviewed their clinical experience with 19 patients treated using an enhanced pinless halo, called the NIH. Advantages of the NIH include the ability to be donned in a supine position because of the absence of a posterior vest, an improved occipital pad that reduces pressure over the posterior skull, and a 40% reduction in cost when compared with a conventional device.205 In their series, Sawers et al.205 reported that all patients healed their fractures, with no additional loss of neurologic function and only one case of fracture subluxation. Furthermore, only one case of pressure ulceration was documented. 

Halothoracic Vest for Cervical Spine Fractures and Dislocations

Halo vest immobilization was used extensively in the past as a definitive means of treatment of many cervical spine injuries.3,35,41,245 However, with the advent of modern spine instrumentation and an increasing number of publications documenting increased complications and failure rates,161,230 the popularity of the halo vest immobilization has diminished recently. Halo fixation is now more frequently employed as a means of facilitating reduction and providing temporary stabilization prior to surgical intervention. The fact that a halo ring can be connected to most Mayfield head rest adapters enhances its versatility, particularly in polytrauma patients who must undergo numerous diagnostic and non–spine-related surgical procedures prior to definitive spine surgery.124 As the halo-thoracic vest maintains the ability to control the end points of the cervical spine, the head, and thoracic regions, these devices remain the most effective nonoperative means of resisting rotational and translational moments.3,168 As a result, they are a viable option for patients with unstable cervical spine injuries who have contraindications to surgery.35,85 It should be recognized, however, that halo fixation has been found to poorly control unstable cervical facet dislocations and is associated with a high failure rate.259 It may also be less useful in perched or locked facets and in the treatment of injuries whose presentation is delayed.45 The halo device does not completely eliminate motion in the subaxial cervical region.3 Intersegmental motion can still occur, especially with attempted flexion and extension of the neck. This results in translation of the subaxial vertebrae relative to each other, a phenomenon that has been referred to as “snaking.”3,205 The device has also been associated with increased mortality rates among the elderly161,230,256 and advanced patient age may be a contraindication.128,161,230 

Application and Technique

Application of the halo vest should be performed with the patient lying flat in a hospital bed or operating room table. The patient remains supine for the entire procedure. The posterior part of the thoracic vest can be placed first by logrolling the patient from side to side and maintaining in-line cervical traction at all times. The anterior part of the vest is then applied and secured using the shoulder straps and side buckles. An appropriately fitted vest should extend down to the level of the xiphoid process, keeping the abdomen free, and be secure enough to maintain its position while still allowing access to the underlying skin. Proper halo vest application has been demonstrated to be the most important factor in maintaining reduction.168 
Next, a small roll of towels is placed behind the occiput. Proposed pin sites should be plotted by provisionally stabilizing the ring to the patient’s head using removable suction devices. These sites should be marked with a pen. The hair should be shaved from the posterior pin sites prior to sterile preparation. The proposed pin sites are then prepped in sterile fashion. The optimal position of the anterior pins is 1 cm above the lateral third of the orbital rim to avoid injury to the supraorbital nerve, whereas the posterior pins should be placed 1 cm above the helix of the ear.35 The pins and ring should not make contact with the ear, as even gentle pressure can lead to skin necrosis over time. Opposing pins should be tightened at the same time to avoid displacement of the ring (e.g., the anterior right pin and the posterior left pin are tightened simultaneously). Optimal pin fixation is achieved when the pins are placed perpendicular to the bone.35 Tightening should be gradual, alternating between the two pairs of opposing pins until the final torque of 8 in.-lb is achieved. The lock nuts are then tightened to prevent pin loosening. Pins should be retightened 24 to 48 hours after halo application. If a pin becomes loose with time, it can be retightened once to 8 in.-lb, as long as resistance is met. If there is no resistance, a new pin should be placed at a different site and the loose pin removed. Even with meticulous pin site care, loosening or infection can occur at pin sites in 6% to 60% of cases.35,205,250 Once the ring has been applied, the longitudinal struts are attached and secured. Cervical radiographs, or fluoroscopic images, are then used to determine cervical alignment, and reduction and careful adjustments can be made to optimize the final position. 

Outcomes

Prior to the advent of modern posterior cervical instrumentation, the halo-thoracic device was used extensively either as the preferred treatment or as an adjunct to provisional stabilization in cervical spine injuries. Within the last 20 years, its popularity has waned, although halo-fixation still remains a viable treatment option, with a well-published record of success in the literature.35,41,45,128,245 For example, Bucholz and Cheung45 documented successful outcomes in 85% of 124 patients treated with halo-thoracic vest for unstable cervical injuries. Similar findings were reported in a more recent study conducted by Bransford et al.41 In this analysis of 342 patients, 85% of those treated with stand-alone halo immobilization were found to have a successful outcome. Healing rates in the range of 50% to 90% have been reported for type II odontoid fractures treated with a halo, and they approach 95% when a halo is used in type III fractures.128 
Several complications have been associated with use of halo-fixation. Pin site loosening and infection are the most common and are reported to occur in 6% to 60% of cases.35,41,128,205,245,250 Van Middendorp and colleagues245 related the incidence of pin site infections to pin penetration through the outer table of the skull. Patients may also experience swallowing difficulty,128 which can be associated with the head and neck being overextended, even in young individuals. Returning the neck to a neutral or slightly flexed position can relieve this in some instances, although the type of injury may prevent this. Pressure sores can develop in 4% to 20% of patients205 and are frequently associated with improper vest fit or loss of sensation due to spinal cord injury. Loss of reduction or alignment can also occur with halo vest immobilization. Van Middendorp et al.245 associated the risk of fracture displacement in a halo with facet joint involvement or dislocation. 
Some of the more serious complications, such as cardiopulmonary events and death, are most likely to occur in the elderly,161,230 leading some to advise against the use of the halo-thoracic vest in this population.128,161 Majercik et al.161 maintained that the mortality in patients older than 65 years was four times that of younger individuals. Similar findings were also documented by Tashjian et al.230 who had a 42% death rate and a complication rate approaching 70% in elderly patients treated with halo-thoracic vests. In contrast, those individuals managed without halo-fixation were reported to have morbidity and mortality rates of 36% and 20%, respectively. It is important to note, however, that other investigations have not encountered increased mortality rates among elderly individuals immobilized with halo-fixation.41,211,245 

Skull-Based Traction and Closed Reduction for Cervical Spine Fractures and Dislocations

Cervical traction is a versatile technique that may be employed in a variety of circumstances. Traction can be used to temporarily immobilize unstable cervical injuries in the at the place of injury or in the emergency room.35,120 This may be advantageous when transferring patients between institutions or for individuals awaiting surgical intervention. 
More often, traction is employed as a means to realign or reduce cervical spine fractures or dislocations. Using this method, the progressive application of weight to the upper cervical region, through the skull, results in distraction forces at the site of injury, realigning fracture fragments through ligamentotaxis, or distracting jumped facets if there is a dislocation. Traction is contraindicated in situations in which occipitocervical dislocation is present, or if there is a high index of suspicion for this injury. In addition, traction is contraindicated if there is a Type IIA traumatic spondylolisthesis. As ligamentous disruption at the occipitocervical joint may not be recognized at first, initial application of weight should be limited to 5 to 10 lb and a lateral radiograph used to assess for distraction at the occipitocervical or atlantoaxial joints. 
Two of the more common devices used to apply traction to the cervical spine are Gardner–Wells (G–W) tongs and the halo ring. In general, G–W tongs are applied more quickly and easily than a halo ring. However, G–W tongs are temporary devices that cannot be used as an adjunct to, or substitute for, spinal stabilization. Traction is applied with a halo device if the planned definitive treatment includes halo-thoracic immobilization, or there is a requirement for an MRI compatible traction ring that can support large reduction forces.151 
Traction can be used to realign and reduce a variety of subaxial spinal injuries. Realignment of an injury can provide some, if not complete, spinal canal decompression. An example of this is the reduction of bilateral facet dislocations. Fracture fragment retropulsion, such as that encountered in burst-type injuries, is often associated with vertebral body height loss and comminution. Following the application of cervical traction, ligamentotaxis can potentially reduce these fragments and produce a degree of indirect canal decompression. However, the success of indirect decompression relies on contiguity of the ligamentous structures and injury severity. Traumatic segmental kyphotic angulation may also be improved by the application of traction. 
Several reports document the safety of using weights of up to 140 lb in reducing facet dislocations in the alert and cooperative patient.64 However, the surgeon must be cognizant of the potential for overdistraction at the level of injury as this may potentiate neurologic compromise.133,206 The biomechanical strength of the traction device is of particular significance if reduction using heavier weights is used.151 Steel G–W tongs are stronger than titanium-alloy or carbon-fiber tongs, although the latter two are MRI-compatible.28 Most contemporary halo rings are also MRI-compatible and may be capable of tolerating higher weights151 because of additional points of fixation. Because pullout strength is diminished with repeated usage, it has been suggested that steel cranial tongs should be recalibrated after frequent usage. The manufacturers recommend that carbon-fiber tongs should be used only once. 

Application Technique

G–W tongs are applied to the skull through two, slightly cranially angulated, fixation pins. Prior to application of any cranial-based traction, plain radiographs or a cranial CT scan should be carefully inspected to rule out skull fractures. The optimal site of insertion is approximately 1 cm, or a finger’s breadth, above the helix of the ear. Neutral pin position is aligned with the external auditory meatus, which best facilitates longitudinal traction. By placing the pins slightly anterior or posterior to this point, extension or flexion moments can be delivered to help reduce kyphotic or hyperlordotic deformities (Fig. 44-23). The skin over the proposed pin site should be marked and sterilized with povidone–iodine or Betadine solution. It is not necessary to shave the site, as it is routinely performed when inserting halo pins. The skin and the underlying periosteum are then anesthetized with a local infiltration of Lidocaine. 
Figure 44-23
Application of Gardner–Wells tongs can be useful in reducing fractures and dislocations.
 
Neutral position is just proximal to the external auditory meatus, about 1 cm above the ear. By placing the pin slightly anterior, an extension moment can be applied. Similarly, by placing the pin slightly posterior, a flexion moment can be applied.
Neutral position is just proximal to the external auditory meatus, about 1 cm above the ear. By placing the pin slightly anterior, an extension moment can be applied. Similarly, by placing the pin slightly posterior, a flexion moment can be applied.
View Original | Slide (.ppt)
Figure 44-23
Application of Gardner–Wells tongs can be useful in reducing fractures and dislocations.
Neutral position is just proximal to the external auditory meatus, about 1 cm above the ear. By placing the pin slightly anterior, an extension moment can be applied. Similarly, by placing the pin slightly posterior, a flexion moment can be applied.
Neutral position is just proximal to the external auditory meatus, about 1 cm above the ear. By placing the pin slightly anterior, an extension moment can be applied. Similarly, by placing the pin slightly posterior, a flexion moment can be applied.
View Original | Slide (.ppt)
X
The tongs are then held in position and the pins are advanced through the skin until they engage the outer cortex of the cranium. Most tongs have an indicator on one pin end that signals when appropriate force has been applied. It is important not to overtighten the pins, as they can penetrate the inner table of the skull, which may result in intracranial injury. However pins that are insufficiently secured can loosen and pullout from the skull, leading to soft-tissue injury, scalp laceration, or temporal artery injury.178 Brain abscess has also been described as a rare complication associated with the use of G–W tongs.162 

Reduction Technique for Odontoid Fractures

G–W tongs are applied as described previously. However, application of a halo ring may be more appropriate in this setting if halo vest immobilization is envisioned as the definitive treatment. With most acute fractures, longitudinal, in-line traction, with a weight of 5 to 30 lb, is usually effective at correcting an angulation deformity. Translational displacement may be more difficult to correct. Rushton et al.201 described the use of “bivector” traction, in which a second traction line is used to deliver an anterior moment, to achieve reduction of posteriorly displaced odontoid fractures. Alternatively, bolsters or towel rolls can be placed behind the head to help reduce posterior translation. Conversely, the thorax can be elevated using bolsters or rolls to facilitate reduction of anteriorly translated odontoid fractures. An initial weight of 5 to 10 lb is applied. This is followed by a lateral radiograph to rule out occult occipitocervical instability or overdistraction across the fracture site, both of which should prompt slow and careful release of traction. Weight is added in 5- to 10-lb increments, with sufficient time allowed between applications to enable stress relaxation of the soft-tissue structures. During this time a lateral radiograph can be obtained and the neurologic status checked. A thorough neurologic examination should be performed between each incremental increase in weight. A change in a patient’s neurologic status warrants immediate attention, including a decrease in the amount of traction weight and further imaging studies. 

Reduction Technique for Bilateral Facet Dislocation

Prior to the application of G–W tongs or a halo ring, a towel roll can be placed between the patient’s scapulae to raise the head slightly off the bed. Because facet reduction requires some flexion in addition to distraction, the pins should be placed about 1 cm posteriorly. The location of the skull equator should be noted. If pins are located above, or cranial to, the equator, they can slide along the slope of the cranium and dislodge. By positioning the pulley anterior to the patient, the traction vector can be used to apply a flexion moment to the cervical spine (Fig. 44-23). Rolled towels can also aid in producing neck flexion, which can help unlock the articular processes. It is important that this traction setup permits subsequent adjustments, as the force vector should be changed to a neutral or slightly extended position once the facets have been reduced. Likewise, the rolled towels are removed after reduction to allow neck extension, which will help hold the reduced facet joints in position. 
As described previously, an initial weight of 5 to 10 lb should be applied, followed by a lateral radiograph to rule out overdistraction through the injured site or a more proximal location, both of which necessitate slow and careful release of traction. Serial neurologic examinations should be performed by the same surgeon in between incremental increases in traction weight, until and even after reduction is achieved. Traction weight is added in 10-lb increments every 10 to 15 minutes, followed by a lateral cervical radiograph, until reduction occurs. While some have advocated that traction weights be limited to 55 or 60 lb, weights as high as 140 lb have been safely used to achieve cervical reductions.64 It is recommended that attempts at reduction using heavy weights be abandoned if the weight applied exceeds two-thirds of patient body weight, distraction across the site of injury exceeds 10 mm, or there is a progression of neurologic deficit. After reduction is radiographically confirmed, the weight is incrementally reduced to 10 to 15 lb and the traction vector adjusted to produce slight neck extension. If magnetic resonance image is to be obtained following reduction, and steel G–W tongs were employed in the reduction, the patient is placed in a rigid cervical collar and the tongs are removed. 

Reduction Technique for Unilateral Facet Dislocations

Unilateral facet dislocations generally result from lower-energy mechanisms than bilateral dislocations. Because of this, they are often stable in the dislocated position and can require comparatively greater amounts of weight to achieve reduction. While some authors have treated these injuries nonoperatively, provided the patient is neurologically intact, most recommend reduction and stabilization.22 
Tongs are applied in the same fashion as for bilateral dislocations, with a flexion moment to facilitate unlocking the dislocated joint. In some cases, a closed reduction maneuver can be performed to achieve an earlier reduction with a lighter weight. The practitioner should grasp the cervical tongs like a steering wheel, with his or her hand placed just above the pins sites (in the 4 and 8 o’clock positions). Axial compression is applied to the nondislocated side, whereas longitudinal distraction is applied to the dislocated side. The dislocated facet should now be unlocked (Fig. 44-24). Final reduction entails reversing the rotational deformity by rotating the head toward the dislocated side. A subtle click or clunk can be heard or felt. Manual traction is then slowly released and a lateral radiograph obtained to confirm the reduction. Once reduced, traction should be decreased to 10 or 15 lb and the neck slightly extended. Neurologic status must be serially assessed throughout the process and especially during an attempt at manipulated reduction.158 
Figure 44-24
Reduction maneuver for a unilateral right-sided facet dislocation.
 
With the tongs in place and weight applied, distractive force is applied to the dislocated side, while compressive force is applied to the nondislocated side. The head is then rotated toward the dislocated side. A satisfying “clunk” signifies that the dislocation has been reduced.
With the tongs in place and weight applied, distractive force is applied to the dislocated side, while compressive force is applied to the nondislocated side. The head is then rotated toward the dislocated side. A satisfying “clunk” signifies that the dislocation has been reduced.
View Original | Slide (.ppt)
Figure 44-24
Reduction maneuver for a unilateral right-sided facet dislocation.
With the tongs in place and weight applied, distractive force is applied to the dislocated side, while compressive force is applied to the nondislocated side. The head is then rotated toward the dislocated side. A satisfying “clunk” signifies that the dislocation has been reduced.
With the tongs in place and weight applied, distractive force is applied to the dislocated side, while compressive force is applied to the nondislocated side. The head is then rotated toward the dislocated side. A satisfying “clunk” signifies that the dislocation has been reduced.
View Original | Slide (.ppt)
X

The Role of Prereduction MRI

The role of prereduction MRI in facet dislocations remains ill-defined. The potential exists for neurologic decline with facet reduction, whether this is performed open or closed.83,158 The cause of neurologic deterioration is believed to be herniation of an intervertebral disc which is pulled into the spinal canal during reduction and then impinges on the spinal cord. Because of this, some authors suggest that an MRI scan be obtained prior to reduction to rule out a disc herniation.83 However, in some centers, the need to obtain an MRI scan prior to reduction will substantially increase the time that the facet joint will be dislocated. If herniated disc material is present, the surgeon may also have to decide whether to undertake an anterior cervical decompression prior to joint reduction. In a series of awake and alert patients, Vaccaro et al.239 performed reductions of facet dislocations, even if disc herniation was present. No instances of neurologic deterioration were reported. 
In the unconscious, head-injured, intoxicated patient, who cannot be adequately examined, with an unknown or unmonitorable neurologic state, a prereduction MRI is advisable. However, in the awake, and alert, patient who can be examined, a prereduction MRI may not be necessary. Two clinical studies have demonstrated that closed reduction of facet dislocation can be performed safely, provided serial neurologic examination can be performed reliably.108,239 In a study undertaken by Vaccaro et al.,239 five of nine patients who underwent a successful closed reduction, without neurologic compromise, had a new herniated disc on postreduction MRI that was not present before reduction. Some patients also had increased signal within the spinal cord postreduction, but no cases of neurologic deterioration were documented. 
Grant et al.108 retrospectively reviewed the results of early closed reduction in a large series of patients with cervical dislocations. Of the 80 individuals who underwent a postreduction MRI, 22% demonstrated a frank disc herniation, although this did not alter the extent, or progression, of any neurologic deficit. In the patient who is awake and alert and experiencing spinal cord compromise or a progressive neurologic deficit, the risks of delaying reduction for the purposes of obtaining an MRI scan are likely to be outweighed by the potential benefit of emergent reduction. In a patient who has dislocated facets but is neurologically intact, it may be reasonable to obtain an MRI scan first, in light of the inherent risk to the spinal cord if a disc herniation is present. Ultimately, the relative advantages and disadvantages of early reduction and anatomical alignment, as compared with the increased complexity of performing anterior decompression and reduction on a dislocated spine, must be weighed on a case-by-case basis. Thus far, no definitive approach has been defined in the literature, and this issue is likely to remain controversial for the foreseeable future. 

Surgical Management of Cervical Spine Fractures and Dislocations

Surgical Timing

The optimal time for surgical intervention, particularly in patients with neurologic deficits, is still undefined in the literature. Although numerous basic science and clinical reports have been published on this topic, no definitive recommendations have been published because of difficulties regarding the definition of early, as opposed to late, surgery as well as limitations in the research methodology of available studies. An example of this is seen in one of the few prospective studies to evaluate outcomes between “early” and “late” surgery where the definition of early surgery was intervention within 72 hours of injury.238 Advocates of early spine surgery, which is generally accepted as within 24 hours of injury,87 maintain that there is an increased chance of neurologic recovery, decreased length of hospital stay, decreased ventilator times, and enhanced patient mobility.50,90,186 There may, however, also be an increased mortality and complications associated with early surgery, particularly in the cervical spine.50 
Basic science studies have almost uniformly supported the benefit of early decompression following spinal cord injury. In one of the most clinically representative spinal cord injury models reported, Dimar and colleagues71 documented a nearly linear relationship between the degree of neurologic recovery and the duration of cord compression in rats. A more recent study by Rabinowitz et al.,191 performed in dogs, revealed that decompressive surgery performed within 6 hours of injury resulted in the best neurologic recovery. This study also showed that surgical decompression, with or without steroid administration, was more effective at facilitating recovery than the use of steroids alone. It should be recognized, however, that outcomes in basic science studies may be influenced by an idealized environment rarely encountered in the clinical setting. An illustrative example of this is the work of Levi et al.,152 which reported that surgical intervention following spinal trauma was possible within 8 hours in only 10% of patients. 
The results of clinical studies have not demonstrated the positive results documented in animal trials. Most older works failed to show benefit from early surgical decompression,90,238,244 although this may have been due to issues with regard to the definition of early surgery.50,89,90 While some authors suggest that surgery be delayed to allow for optimal medical and surgical stabilization and the resolution of spinal cord edema, others have demonstrated that interventions performed within 24 hours of injury are safe and effective.90,157,253 
One prospective series demonstrated no difference in patients with acute spinal cord injury operated within 72 hours of injury and those receiving treatment after 5 days or more.238 However, in a review of 91 patients, Papadopoulos et al.186 reported a 59% rate of neurologic improvement for those receiving “immediate” decompression. Similarly, in a meta-analysis, La Rosa and colleagues146 documented a 90% improvement among patients with incomplete spinal cord injuries who received surgery within 24 hours. In this same study, the rates of neurologic recovery for patients with complete spinal cord injury were 42% if surgery was performed within 24 hours and 8% and 58%, respectively, if surgery was delayed for complete and incomplete injuries. These authors declared, however, that because of heterogeneity, only those findings related to incomplete spinal cord injury were reliable.146 
In two separate systematic reviews, Fehling and his coworkers’ group89,90 recommended surgical decompression within 24 hours of spinal cord injury whenever possible. Based on a survey of an international group of spine surgeons, these authors also reported that most surgeons recommend decompression of the acutely injured spinal cord within 24 hours, and even earlier intervention is proposed in the event of incomplete injury.90 In a separate systematic analysis, Carreon and Dimar50 found that early surgical intervention was associated with shorter hospital stay and length of time in the intensive care unit, fewer ventilator days, decreased risk of pulmonary complications, and lower hospital costs. However, in this study, early surgical intervention for cervical injuries was associated with an increased complication rate (58% for early surgery as compared with 47.5% in late surgery) and risk of mortality (4.5% for early surgery vs. 3.3% for late).50 It is likely that the debate regarding timing of surgical intervention will persist until level I evidence from a scientifically rigorous, multicenter, prospective trial becomes available. It has been suggested that one such study, the Surgical Treatment of Acute Spinal Cord Injury Study, is being capable of providing such definitive evidence.87,90 However, no published peer-reviewed data are presently available. 

Surgical Techniques for Cervical Spine Fractures and Dislocations

Anterior Approaches to the Cervical Spine

Transoral Approach
Although rarely needed, direct exposure of the anterior atlantoaxial region can be achieved through a transoral approach. Successful fusion and instrumentation procedures have been reported, but the transoral approach is probably best reserved for excisional procedures, such as the excision of a displaced odontoid nonunion, because there is a higher risk of infection if bone graft or implants are inserted. Endotracheal intubation is preferred, as the tube is easily positioned out of the operating field. A specially designed, rectangular-shaped self-retaining retractor is used to access the oropharyngeal mucosa. Four fascial layers are crossed to access the spine: the pharyngeal mucosa, the pharyngeal constrictor muscles, the buccopharyngeal fascia, and the prevertebral fascia. A scalpel is used to incise through the ALL down to vertebral bone. The entire soft-tissue layer is then stripped subperiosteally using a periosteal elevator. Electrocautery should be avoided as it damages the tissue edges and can make closure difficult. After a transoral approach, extubation must be delayed until laryngeal and pharyngeal edema sufficiently resolve. Failure to do so can lead to acute respiratory compromise, necessitating emergent reintubation through swollen tissues. 

High Anterior Retropharyngeal Approach

The prevascular retropharyngeal approach can be used to access the skull base down to C3. While rarely necessary, it can allow anterior access to the C1 ring, odontoid process, and the C2–C3 disc space while avoiding the inherent contamination problems associated with the transoral exposure. Procedures that can be performed via this approach include anterior cervical discectomy and fusion of C2–C3, odontoidectomy, and osteosynthesis of the anterior C1 ring. It is readily extended distally into an expansile anterior cervical approach. 
A submandibular skin incision is used. After the platysma is divided in line with the incision, the following structures should be identified. The submandibular gland is visualized at the posterior angle of the jaw, underneath the mandible, whereas the parotid gland lies on top of the bone. Lying deep to the parotid gland is the marginal mandibular branch of the facial nerve. This is a purely motor branch, which innervates the lower lip for puckering and depression. The retromandibular vein generally crosses the central aspect of the parotid gland. The common facial vein crosses the anterior aspect of the masseter muscle along the inferior angle of the jaw. These two veins should be dissected free and ligated near their junctions with the internal jugular vein, allowing the soft-tissue flaps to be retracted. Keeping the dissection deep to, and inferior to, these ligated veins helps protect the facial nerve branch from injury. Next, the medial border of the sternocleidomastoid is developed and the submandibular gland is resected carefully to protect the facial nerve at all times. The salivary duct, which is located deep to the gland, must be identified and ligated to prevent cutaneous fistula formation. The stylohyoid and digastric muscles are dissected free, transected near their hyoid insertions, tagged, and reflected superiorly along with the hypoglossal nerve, which runs deep to them. At this time, the plane of dissection progresses between the carotid sheath and the esophagus and larynx medially, just as in the lower cervical approach, except that numerous anteriorly projecting branches from the carotid and internal jugular vessels must be ligated. Potential complications include facial nerve palsy, this being the most common complication, iatrogenic esophageal perforation, vascular injury, or damage to the other exposed nerves such as the superior laryngeal, recurrent laryngeal, hypoglossal, and glossopharyngeal nerves. 

Anterior Approach to the Subaxial Cervical Spine

The standard Smith–Robinson approach can be utilized to access most of the cervical spine anteriorly (Fig. 44-25). Depending on the size of the patients and their stature, as well as the length of their neck, a standard anterior approach to the cervical spine can safely access the subaxial region from the C2–C3 disc space proximally to the level of T1. The approach exploits the plane between the sternocleidomastoid laterally, and the strap muscles of the neck, the sternohyoid and the thyrohyoid, medially. The surgical incision is based on the desired level of exposure and palpation of structural landmarks such as the hyoid bone at the level of C3, the thyroid cartilage at the level of C4–C5, and the cricoid cartilage or carotid tubercle at C6. If one or two cervical levels are to be exposed, a transverse incision along a skin crease can be employed and results in a more cosmetic scar. If three or more levels are to be exposed, a longitudinal incision parallel to the anterior border of the sternocleidomastoid is used. Following the skin incision, the platysma is divided in line with its muscle fibers. The deep cervical fascia, which invests the sternocleidomastoid, is then incised along the anterior border of that muscle. Palpation is used to identify the carotid sheath and, with blunt retractors protecting the soft-tissue structures medially and laterally, the pretracheal fascia is separated medial to the carotid sheath. The prevertebral fascia may be swept away using blunt dissection with peanut sponges on a Kidner instrument. The longitudinal fibers of the ALL are then visualized spanning the vertebral bodies and intervertebral discs. Disruption of the ALL or hemorrhage in the vicinity of a vertebral body, or disc space, may indicate the traumatized level. A left-sided approach is the authors’ preference due to the theoretically reduced risk of injury to the recurrent laryngeal nerve because of its more predictable course on this side. However, in a study of 418 patients undergoing anterior cervical approaches, Kilburg et al.140 found no significant difference in the incidence of recurrent laryngeal nerve injury based on the side of exposure. 
Figure 44-25
Anterior approach to the subaxial cervical spine.
 
The superficial interval is between the sternocleidomastoid muscle (lateral) and strap muscles (medial). Deep dissection is between the carotid sheath (lateral, which contains the carotid artery, internal jugular, and recurrent laryngeal nerve) and the trachea/esophagus. The alar and prevertebral fascia (deepest) are swept away to access the anterior longitudinal ligament, vertebral bodies, and disc spaces.
The superficial interval is between the sternocleidomastoid muscle (lateral) and strap muscles (medial). Deep dissection is between the carotid sheath (lateral, which contains the carotid artery, internal jugular, and recurrent laryngeal nerve) and the trachea/esophagus. The alar and prevertebral fascia (deepest) are swept away to access the anterior longitudinal ligament, vertebral bodies, and disc spaces.
View Original | Slide (.ppt)
Figure 44-25
Anterior approach to the subaxial cervical spine.
The superficial interval is between the sternocleidomastoid muscle (lateral) and strap muscles (medial). Deep dissection is between the carotid sheath (lateral, which contains the carotid artery, internal jugular, and recurrent laryngeal nerve) and the trachea/esophagus. The alar and prevertebral fascia (deepest) are swept away to access the anterior longitudinal ligament, vertebral bodies, and disc spaces.
The superficial interval is between the sternocleidomastoid muscle (lateral) and strap muscles (medial). Deep dissection is between the carotid sheath (lateral, which contains the carotid artery, internal jugular, and recurrent laryngeal nerve) and the trachea/esophagus. The alar and prevertebral fascia (deepest) are swept away to access the anterior longitudinal ligament, vertebral bodies, and disc spaces.
View Original | Slide (.ppt)
X

Anterior Decompression

Anterior decompression of the cervical spine can be achieved via discectomy or vertebral body corpectomy. The decision regarding the type of decompression should be determined prior to surgery in most instances and is based on the extent of vertebral body fracture, the presence of comminution, and the location of compressive pathology within the spinal canal. Vertebral body fractures that involve sizable portions of the endplate, or that are substantially comminuted, cannot be utilized as viable docking points for strut grafts or fixation points for screws. 
A discectomy can be performed if a herniated disc is the only structure compressing the neural elements. In certain instances, the herniation may be extruded or displaced behind the adjacent vertebral body in a cephalad or caudal position. This situation may necessitate partial, or complete, corpectomy to safely access the disc fragment and ensure its complete removal. 
In the event that the vertebral body is fractured, loose fragments may be excised piecemeal with a rongeur. If reconstruction is planned using an expandable cage or titanium mesh, the bone should be retained for graft. Alternatively, a high-speed burr can be used to remove the damaged vertebral body. Preoperative CT scans must be consulted prior to corpectomy to rule out the presence of an anomalous vertebral artery.69 Before beginning the corpectomy, the uncovertebral joints should be identified. These herald the lateral margins of the vertebral body, with the unprotected vertebral artery approximately 5 mm lateral to these processes at the level of the disc space. The corpectomy trough should be plotted to be 15 to 16 mm in width and should not extend beyond the uncovertebral joints. If a burr is used to perform the corpectomy, all cancellous bones should be removed from within the site until the posterior cortical margins are visualized. These can then be elevated with a Woodson elevator and excised using Kerrison rongeurs. If the PLL is intact following the trauma, it is likely that it does not need to be removed unless compressive epidural hematoma is located beneath it. If the PLL was already disrupted during the initial injury, it is frequently removed attached to pieces of vertebral body bone and the spinal cord will be visible within the canal. 

Anterior Reduction of Dislocated Facets

If a herniated cervical disc was identified by MRI to be associated with a facet dislocation, an anterior discectomy may need to be performed prior to an attempt at reduction. There are several techniques that can be used to reduce the dislocation once a discectomy has been performed. A lamina spreader may be placed between the vertebral endplates to distract the injured segments, unlock the dislocated joints, and facilitate reduction (Fig. 44-26). If this technique is used, care must be taken to avoid overdistraction, as this can result in spinal cord injury. Another method relies on Caspar pins that are placed into the vertebral bodies. The pins are then used to manipulate the vertebral segments, and the cephalad vertebra is levered over the caudal body without substantial distraction. Once reduction has been achieved, intraoperative fluoroscopic image or lateral plain film is used for confirmation. Irreducible dislocations may require additional posterior surgery to allow reduction. 
Figure 44-26
Open reduction of dislocated facets using an anterior approach.
 
A laminar spreader can be used to distract and unlock the injured articular processes.
A laminar spreader can be used to distract and unlock the injured articular processes.
View Original | Slide (.ppt)
Figure 44-26
Open reduction of dislocated facets using an anterior approach.
A laminar spreader can be used to distract and unlock the injured articular processes.
A laminar spreader can be used to distract and unlock the injured articular processes.
View Original | Slide (.ppt)
X

Reconstruction

Following a complete decompression, the superior and inferior endplates of the adjacent vertebral bodies are denuded of cartilage and lightly burred until punctate bleeding is present. If overhanging osteophytes are located at the vertebral margins, these should be rongeured such that a flat surface is available to accept plate placement. The corpectomy or discectomy site is measured to determine the appropriate size of the interbody graft or strut. A variety of implants, as well as autograft and allograft struts, are available to reconstruct the anterior cervical spine. Implants include titanium mesh cages, expandable cages, and polyethylene-ether-ketone cages. Structural autograft is obtained from the iliac crest. 
The graft should be fashioned to match the length, width, and height of the postdecompression defect. Additional manual traction on the mandible may be performed by a member of the anesthesia team as the graft is gently impacted into place between the vertebral bodies. In the case of expandable cages, no distraction is necessary, and the cage should be expanded until there is an intimate fit between the graft and the host bone. Because of the fact that many traumatic injuries result in cervical instability that permits overdistraction, axial compression on the head following graft placement can help achieve graft–host bone approximation. 
The advantage of using interbody implants, such as titanium mesh or expandable cages, lies in the fact that corpectomy bone can be recycled and packed inside. This diminishes the morbidity associated with iliac crest bone graft harvest. A more theoretical advantage is enhanced bone incorporation and fusion because the cage is packed with cancellous rather than cortical bone.75 Inert implants are also not subject to resorption, although cages with minimal endplate contact area may be at risk of subsidence in osteopenic bone, or if the endplates are violated. There are now implants available with larger endplate footprints intended to prevent subsidence. 

Anterior Instrumentation

Anterior stabilization is performed after the graft is inserted. Anterior plating is used to stabilize discectomy and corpectomy defects. The positioning of the screws and cortical purchase are critically important in ensuring stabilization and to encourage fusion. Initially, the plate is centered over the anterior vertebral bodies and is held in place with provisional pins. Pilot holes can be drilled, or self-tapping, self-drilling screws may be inserted if they are available. Pilot holes should be angled away from the endplate, and 10 to 15 degrees toward the midline, to avoid inadvertent penetration of the vertebral artery. Screw length should be calculated from preoperative imaging studies and confirmed by direct measurement if necessary. If locking screws are used, measurement is necessary only to ensure that the screws are not so long as to penetrate the spinal canal. In a single-level discectomy or corpectomy, four screws are inserted, two cranially and two caudally. 
Historically, bicortical screws were used for anterior plate fixation following cervical trauma. However, with recent advances in plates and screws, including locked-plate fixation, bicortical instrumentation is no longer performed by most surgeons. Fixed angle screws that lock into the plate maintain equivalent, if not superior pullout strength to bicortical plate and screw devices.112 Locking screws also minimize the risk of anterior screw migration. First-generation locking plates allowed only fixed angle insertion of screws, which made insertion difficult in some instances. Newer designs now allow variable angle screw placement that allows immediate rigid fixation or a degree of slight settling. 
Dynamic plates, that allow vertical settling in the postoperative period, should not be used as internal fixation devices following cervical spine trauma. Thin, low-profile plates may be suboptimal as well, given that they have reduced biomechanical strength as compared with thicker plates. 
While they are rare in trauma, cervical corpectomies that extend beyond two levels should not be reconstructed with stand-alone anterior fixation because of a high risk of failure.204,240 In these instances, additional posterior fixation is necessary even if posterior decompression is not performed. Similarly, multilevel corpectomies that end at T1 should be supplemented with posterior instrumentation that spans the cervicothoracic junction.6 

Published Results

There are relatively few studies specifically examining results following anterior decompression and instrumentation for cervical trauma. Garvey et al.101 reported satisfactory outcomes in 14 patients treated with anterior Caspar plate fixation and fusion for subaxial cervical fractures and dislocations. No cases of fixation failure had been observed at an average follow-up of 30 months. Similar results were reported in the series of Randle et al.,193 which documented 6-month outcomes for traumatic injuries treated with anterior plate fixation. Goffin et al.103 published 5- to 9-year results in 25 patients treated with anterior fusion and plating for cervical fractures and dislocations. Fusion was demonstrated in all cases by 1 year, with hardware failure occurring in only one instance. Similar to findings in the nontrauma literature, 60% of patients in this series demonstrated evidence of adjacent segment degeneration, although this did not correlate with clinical complaints.103 
More recently, Kwon et al.144 reviewed their results in patients treated with anterior plate fixation in a randomized prospective trial of unilateral facet injuries. This study found that anterior plate fixation, as compared with posterior instrumentation, resulted in less postoperative pain, a decreased risk of wound infection, increased fusion rates, and better maintenance of sagittal alignment. Brodke et al.43 also compared outcomes between anterior and posterior surgery, with unstable cervical burst fractures being the focus of their work. While fusion rates were similar, neurologic recovery was higher with anterior decompression and fusion (70% in the anterior group vs. 57% in those who underwent posterior surgery). In a series of 19 patients treated with anterior cervical discectomy and fusion for unstable posterior injuries, Woodworth and colleagues261 reported an 88% fusion rate with neck disability scores, indicating mild or no disability for all patients at final follow-up. Most importantly, no cases of neurologic deterioration following treatment were reported. 

Posterior Approaches to the Cervical Spine

Posterior Approach to the Cervical Spine

The posterior approach to the cervical spine is a midline, extensile approach that can be extended from the occipitocervical junction to the lumbosacral articulation. The dissection can be relatively bloodless if maintained within the avascular plane of the ligamentum nuchae, which separates the right and left paraspinal musculature. Intramuscular hemorrhage and posterior interspinous and supraspinous process ligament damage are often apparent at the level of injury. It is important to maintain the integrity of any uninjured ligaments, until the correct surgical level is identified, to avoid unnecessary destabilization of adjacent segments. Subperiosteal dissection is started on either side of the bifid spinous process, continued down to the spinolaminar junction, and extended laterally over the laminae. Further dissection onto the lateral masses and facet joints should occur only at the levels to be fused. 
Particular care must be taken with exposure of the upper cervical spine. Classically, it is recommended that lateral dissection along the posterior C1 ring be restricted to within 1.5 cm from the posterior midline to avoid injury to the vertebral artery (Fig. 44-17). The artery is located along the superior aspect of the C1 ring approximately 1 cm from the midline. More lateral exposure of the ring can be safely performed along the inferior aspect of C1. Exposure of this region is often necessary to facilitate the insertion of lateral mass screws into C1.116 Surgeons should note the presence of a ponticulus posticus, or osseous enclosure of the vertebral artery at C1, which may be present in as many as 16% of patients.263 The presence of a ponticulus posticus may be appreciated on axial or sagittal CT scans. While the osseous enclosure around the vertebral artery can offer some protection during exposure, it should not be erroneously interpreted as a starting point for C1 screw insertion. 
Similarly, exposure of the superior aspect of the C2 ring should proceed with caution to avoid inadvertent entry into the spinal canal, which is not protected by the ligamentum flavum at this level. Bipolar cautery is recommended for exposure of the C2 pedicle to allow cauterization of the leash of veins in this location and limit bleeding. The C2 nerve root can be visualized, as it lies along the posterior surface of the C1–C2 joint. It usually needs to be retracted superiorly or inferiorly to expose the posterior aspect of the C1 lateral mass. Alternatively, it can be ligated, although this will result in anesthesia in a portion of the posterior scalp. 

Decompression

In most cases of acute traumatic cervical injury, posterior decompression via laminectomy is not necessary. Canal compromise is most often caused by dislocation, translation, or retropulsed vertebral body fragments. In rare cases of anteriorly displaced posterior arch fragments, a laminectomy is indicated to directly remove the offending compressive elements. This is not true, however, in cases of acute spinal cord injury associated with multilevel spondylotic stenosis, or ossification of the PLL, in which a posterior decompressive procedure can be considered the procedure of choice if cervical lordosis has been maintained. 
If a posterior cervical decompression is to be performed, the appropriate levels are identified during exposure and dissection is carried out over the spinous process, laminae, and facet joints. The decompression should start centrally involving the spinous processes and laminae to the junction with the lateral masses. If loose fracture fragments are already present, they can be removed with a rongeur or delivered using a small curette and excised with pituitary forceps. Alternatively, the spinous processes may be resected with a rongeur and the laminae burred down to a thin cortical layer. The decompression is completed by removing the cortical bone and ligamentum flavum with Kerrison rongeurs. Another approach is to resect the osseous junction between the lamina and the lateral mass over the entire area that is to be decompressed and then to remove the piece, en bloc, with the assistance of bone clamps. In general, this technique is more applicable to degenerative conditions and is less useful in spinal trauma. 

Reduction Maneuvers for the Upper Cervical Spine

If acceptable alignment is not obtained by closed methods prior to surgery, direct intraoperative reduction maneuvers can be performed. Reduction of an anteriorly displaced C1 ring, resulting from C1–C2 ligamentous instability, an odontoid fracture, or a hangman’s fracture can be achieved by pulling an intact C1 ring posteriorly under fluoroscopic guidance. While a towel clip may be used, a sublaminar wire or cable inserted underneath the C1 ring is equally effective and provides potentially better control (Fig. 44-27). Posterior displacement can be more difficult to reduce. To do this, an anterior force should be carefully delivered to the C1 ring, if intact. For bayoneted odontoid fragments, a Penfield elevator can be inserted posterolaterally around the spinal cord, into the fracture site, to enable the proximal fragment to be levered over the distal fragment (Fig. 44-28). As a last recourse, reduction can be performed using screws inserted into the occiput, C1, or C2. 
Figure 44-27
 
After posterior exposure has been performed, anterior displacement of the C1 ring can be reduced by delivering a posterior force via towel clips. Note that the atlanto-dens interval has been reduced in the lower figure.
After posterior exposure has been performed, anterior displacement of the C1 ring can be reduced by delivering a posterior force via towel clips. Note that the atlanto-dens interval has been reduced in the lower figure.
View Original | Slide (.ppt)
Figure 44-27
After posterior exposure has been performed, anterior displacement of the C1 ring can be reduced by delivering a posterior force via towel clips. Note that the atlanto-dens interval has been reduced in the lower figure.
After posterior exposure has been performed, anterior displacement of the C1 ring can be reduced by delivering a posterior force via towel clips. Note that the atlanto-dens interval has been reduced in the lower figure.
View Original | Slide (.ppt)
X
Figure 44-28
 
In challenging cases that do not reduce by conventional closed or open methods, a Penfield elevator can be carefully inserted posterolaterally into the odontoid fracture site (A). It should be advanced just beyond the anterior aspect of the proximal fragment under lateral fluoroscopy (B). The instrument is then levered superiorly to unlock the fracture fragments and restored alignment (C).
In challenging cases that do not reduce by conventional closed or open methods, a Penfield elevator can be carefully inserted posterolaterally into the odontoid fracture site (A). It should be advanced just beyond the anterior aspect of the proximal fragment under lateral fluoroscopy (B). The instrument is then levered superiorly to unlock the fracture fragments and restored alignment (C).
View Original | Slide (.ppt)
Figure 44-28
In challenging cases that do not reduce by conventional closed or open methods, a Penfield elevator can be carefully inserted posterolaterally into the odontoid fracture site (A). It should be advanced just beyond the anterior aspect of the proximal fragment under lateral fluoroscopy (B). The instrument is then levered superiorly to unlock the fracture fragments and restored alignment (C).
In challenging cases that do not reduce by conventional closed or open methods, a Penfield elevator can be carefully inserted posterolaterally into the odontoid fracture site (A). It should be advanced just beyond the anterior aspect of the proximal fragment under lateral fluoroscopy (B). The instrument is then levered superiorly to unlock the fracture fragments and restored alignment (C).
View Original | Slide (.ppt)
X

Reduction Maneuvers for the Subaxial Cervical Spine

Usually, the primary goal of posterior surgery in subaxial cervical trauma is reduction and/or stabilization. Open reduction of dislocated facet joints can be performed through a posterior approach. Cervical traction can facilitate intraoperative maneuvers by providing distraction across the dislocated segments. If the spinous processes are intact, they can be grasped with towel clips near their base to flex and distract the injured joint. If the spinous processes are fractured, a Penfield 4 elevator, or other small flat instrument, may be placed over the top of the superior articular process of the lower vertebral level. Then, angling it caudally, the inferior tip of the inferior articular process from the upper level can be levered up and posteriorly, back into position (Fig. 44-29). If these maneuvers fail, then the tip of the superior articular process of the lower vertebra can be resected using a burr or small Kerrison rongeur (Fig. 44-30). 
Figure 44-29
Open reduction of dislocated facets using a posterior approach.
 
A Penfield 4 elevator (or other small, smooth, elevator) is inserted over the superior articular process. It is walked inferiorly to hook the inferior (dislocated) articular process. The elevator is then levered caudally to reduce the joint.
A Penfield 4 elevator (or other small, smooth, elevator) is inserted over the superior articular process. It is walked inferiorly to hook the inferior (dislocated) articular process. The elevator is then levered caudally to reduce the joint.
View Original | Slide (.ppt)
Figure 44-29
Open reduction of dislocated facets using a posterior approach.
A Penfield 4 elevator (or other small, smooth, elevator) is inserted over the superior articular process. It is walked inferiorly to hook the inferior (dislocated) articular process. The elevator is then levered caudally to reduce the joint.
A Penfield 4 elevator (or other small, smooth, elevator) is inserted over the superior articular process. It is walked inferiorly to hook the inferior (dislocated) articular process. The elevator is then levered caudally to reduce the joint.
View Original | Slide (.ppt)
X
Figure 44-30
 
A Kerrison rongeur can be used to resect the superior aspect of the articular process if open reduction maneuvers are not successful.
A Kerrison rongeur can be used to resect the superior aspect of the articular process if open reduction maneuvers are not successful.
View Original | Slide (.ppt)
Figure 44-30
A Kerrison rongeur can be used to resect the superior aspect of the articular process if open reduction maneuvers are not successful.
A Kerrison rongeur can be used to resect the superior aspect of the articular process if open reduction maneuvers are not successful.
View Original | Slide (.ppt)
X

Posterior Instrumentation and Fusion of the Cervical Spine

Published Results

There are few published reports of the results of internal fixation or instrumented fusion for traumatic injuries of the upper cervical spine. The limited available data is discussed below in more detail, categorized by injury type. Most available series detail the use of historical techniques using wire fixation, such as Gallie and Brooks fusion. The results of modern instrumentation techniques in upper cervical trauma have not been well reported. 

Authors’ Preferred Method of Treatment for Cervical Spine Fractures and Dislocations

 
 
Posterior Stabilization and Fusion of the Upper Cervical Spine
 

In general, segmental screw and rod instrumentation systems are preferred. The occiput is instrumented using a midline plate fixed just inferior to the external occipital protuberance. Contoured rods, or manufactured rods with a hinge, are used to span the occipitocervical junction. These can connect to C2 pedicle screws, spanning the C1 ring, and C1 lateral mass screws may be employed if additional fixation is required. Fixation at the atlantoaxial articulation is performed using C1 lateral mass screws connected to the C2 isthmus, or pedicle screws, using a variable angle screw–rod system. Fusion is achieved using autogenous bicortical iliac crest bone graft secured with braided cables.

 
Posterior Stabilization and Fusion of the Lower Cervical Spine
 

The earliest forms of posterior cervical stabilization entailed the use of wire-based constructs, which are still employed today. The simplest form of wire stabilization is interspinous process wiring. Using a drill bit or a 2- or 3-mm burr, a hole is created on either side of the superior third of the spinolaminar junction of the upper vertebra. Next, the hole is completed from side-to-side by puncturing the bone with a towel clip or sharp bone clamp. One or more wires or ideally a braided cable is passed through the hole and then transferred beneath the spinous process of the lower vertebra. The wire or cable is then tensioned. Alternatively, the wire can be passed through a hole in the inferior third of the spinolaminar junction of the lower vertebra.197 A triple-wiring technique has also been described, which incorporates fixation of corticocancellous struts on either side of the spinous processes. The advantage of wiring techniques is that they are a relatively inexpensive method of posterior stabilization with nearly equivalent restoration of stability as some lateral mass plating systems.168 The disadvantages are that such a technique cannot be used if a laminectomy has been performed, or in the presence of posterior element fractures. Adjuvant external immobilization, such as a halo-thoracic vest, may also be necessary, for periods up to 6 months, to achieve an optimal result if stand-alone wire constructs are used.

 

Facet wiring has been advocated as an alternative to interspinous wiring in that it can be performed in the presence of a laminectomy or posterior element fractures. Stability in this technique, however, is still reliant on the structural properties of bone graft. In addition, the inferior wire construct is passed across a joint that is not fused or included in the fixation construct. Stability may be enhanced by wiring the facets to a longitudinal rod or Luque rectangle.65

 

Lateral mass screw fixation has gained increased popularity within the last 10 to 15 years. These screws can be inserted using several different techniques (Fig. 44-31). The Roy-Camille technique orients the lateral mass screws perpendicularly to the long axis of the spine, making fixed-angle screw fixation to a rod easier at the expense of shorter screw lengths, reduced pullout strength, and greater risk of injury to the vertebral artery. The Magerl method of screw insertion maintains the advantages of greater screw length and enhanced biomechanical properties. With the screw tip directed toward the level of the disc space, the exiting nerve root may be at greater risk, whereas there is reduced risk of vertebral artery injury. The An technique, in which screws are inserted with a trajectory of 30 degrees lateral and 15 degrees cephalad, parallels the orientation of the facets and probably carries the lowest risk of neurovascular compromise.7,139

 
Figure 44-31
Magerl (left) and Roy-Camille (right) techniques of inserting lateral mass screws.
Rockwood-ch044-image031.png
View Original | Slide (.ppt)
X
 

Variable-angle titanium screws that interface with longitudinal connector rods (Fig. 44-32) have largely supplanted cervical plate fixation because of the fact that variable angle screws can accommodate minor differences in medial–lateral and proximal–distal variations in screw position. Polyaxial lateral mass screw–rod systems also permit optimal screw placement, this being determined by the anatomy of the patient and the nature of cervical injury, rather than being restricted to the positions of the holes within the cervical plate.

 
Figure 44-32
 
Side view (A) and posterior view (B) of a diagram depicting a variable angle posterior screw–rod construct for stabilization of lower cervical spine injuries.
Side view (A) and posterior view (B) of a diagram depicting a variable angle posterior screw–rod construct for stabilization of lower cervical spine injuries.
View Original | Slide (.ppt)
Figure 44-32
Side view (A) and posterior view (B) of a diagram depicting a variable angle posterior screw–rod construct for stabilization of lower cervical spine injuries.
Side view (A) and posterior view (B) of a diagram depicting a variable angle posterior screw–rod construct for stabilization of lower cervical spine injuries.
View Original | Slide (.ppt)
X
 
Published Results
 

In a series of 162 patients with flexion injuries treated using posterior interspinous process wiring techniques, Lee et al.149 reported a100% fusion rate. However, residual kyphosis was present in 34% of patients and translational or hyperlordotic deformity was evident in 13% of cases. These findings indicate that although a high fusion rate can be achieved with wiring techniques, maintenance of sagittal alignment can be a challenge.

 

Roy-Camille et al.199 used posterolateral mass screws and plates to treat 197 patients with lower cervical spine injuries. Final radiographic follow-up demonstrated that initial reduction and alignment was maintained in 85% of cases. Nazarian and Louis176 used posterior screws and lateral mass plates in 23 cases of cervical fracture and reported excellent maintenance of alignment and high fusion rates. As part of a prospective, randomized controlled trial for unilateral facet injuries, Kwon and colleagues144 reported no difference in patient-based outcome measures between anterior and posterior fixation.

Authors’ Preferred Method of Treatment for Cervical Spine Fractures and Dislocations

 
 
Stabilization of the Lower Cervical Spine
 

The authors prefer to use variable-angle screw–rod constructs to stabilize the cervical spine after traumatic injuries. The ability to place screws in the optimal position, followed by fixation to an appropriately contoured rod, is considered a major advantage. In addition, individual screws and levels can be compressed and distracted to achieve maximal correction and reduction.

 

The starting point for the lateral mass screw is 1 mm medial and inferior to the hillock of the lateral mass in the coronal plane and midway between the surfaces of the superior and inferior articular process (Fig. 44-33). A 2-mm burr is used to start the hole. A hand drill is then inserted into the starting hole and angled laterally by about 30 degrees. It is parallel to the facet joint in the sagittal plane. This can be judged clinically by placing a thin, flat instrument into the joint to be fused but can also be assessed using intraoperative fluoroscopy. Drilling proceeds carefully up to, but not through, the second cortex, as bicortical fixation has not been demonstrated to be of biomechanical advantage.187

 
Figure 44-33
The authors’ preferred technique is a modified An method.
 
A starting hole is created with a 2-mm burr bit. Dividing the lateral mass into quadrants, it is located at the superolateral aspect of the inferomedial quadrant (A). The screw is then angled laterally about 25 to 30 degrees (B). In the sagittal plane, the screw path is kept perpendicular to the plane of the adjacent facet joint (C). This method allows placement of the screw within the midaspect of the lateral mass. Unicortical purchase is preferred.
A starting hole is created with a 2-mm burr bit. Dividing the lateral mass into quadrants, it is located at the superolateral aspect of the inferomedial quadrant (A). The screw is then angled laterally about 25 to 30 degrees (B). In the sagittal plane, the screw path is kept perpendicular to the plane of the adjacent facet joint (C). This method allows placement of the screw within the midaspect of the lateral mass. Unicortical purchase is preferred.
View Original | Slide (.ppt)
Figure 44-33
The authors’ preferred technique is a modified An method.
A starting hole is created with a 2-mm burr bit. Dividing the lateral mass into quadrants, it is located at the superolateral aspect of the inferomedial quadrant (A). The screw is then angled laterally about 25 to 30 degrees (B). In the sagittal plane, the screw path is kept perpendicular to the plane of the adjacent facet joint (C). This method allows placement of the screw within the midaspect of the lateral mass. Unicortical purchase is preferred.
A starting hole is created with a 2-mm burr bit. Dividing the lateral mass into quadrants, it is located at the superolateral aspect of the inferomedial quadrant (A). The screw is then angled laterally about 25 to 30 degrees (B). In the sagittal plane, the screw path is kept perpendicular to the plane of the adjacent facet joint (C). This method allows placement of the screw within the midaspect of the lateral mass. Unicortical purchase is preferred.
View Original | Slide (.ppt)
X
 

A depth gauge is then inserted to determine screw length. In the authors’ experience, preoperative CT scanning is often of limited use in estimating screw length. In most cases, a 12- or 14-mm screw can be inserted. Screw holes should be tapped, as the bone of the lateral mass can be quite dense. The 3.5-mm screw is then inserted and finger tightened. Attempts to overtighten screws can easily strip the hole, which may necessitate placement of a 4.0-mm screw to rescue the situation. Too cephalad or caudal screw placement can risk violation of the articular surfaces. If the starting point is too lateral, the lateral mass can fracture, which may preclude adequate fixation at that level.

 
Posterior Fusion
 

The articular surfaces of the facets should be decorticated using a small microcurette prior to the placement of a connector rod. A 3-mm burr is then used to lightly decorticate the lateral masses. If screws have been placed, it is important to not remove too much bone, as this may weaken the region surrounding the screw and lead to failure. If the laminae and spinous processes are intact, then their posterior surfaces should also be decorticated to a bleeding surface. Cancellous bone harvested from the posterior iliac crest is then packed inside the facet joints. The connector rods are then placed and fixed into position with blocking-screw caps. Additional bone graft is laid over the posterior elements and lateral masses.

 
Postoperative Care
 

The advantage of rigid internal fixation for cervical spinal injuries is that the need for postoperative external immobilization is usually decreased or even obviated. However, this should be determined on a case-by-case basis and is usually dictated by the type of fixation and bone quality. While a polyaxial screw–rod construct in normal bone may not necessitate external immobilization, this may not be the case in the presence of osteoporosis, or if wire fixation was used. In the authors’ practice, a rigid cervical collar is prescribed for 6 weeks in awake and alert patients who will be ambulatory following surgery. In polytrauma patients who are still ventilator-dependent postoperatively, an orthosis is avoided to facilitate nursing and respiratory care. With rigid internal fixation, the patient can be seated to facilitate pulmonary toilet and clearance of secretions. If indicated, postoperative antiembolic chemoprophylaxis can be started on postoperative day 4 or 5 so as to avoid an epidural hematoma. Prophylactic antibiotics are continued for 48 hours in these situations.

Complications of Surgery in Cervical Spine Fractures and Dislocations

Complications Associated with the Anterior Approach

The most common complication following anterior cervical surgery is dysphagia or difficulty in swallowing, which can occur in as many as 50% of cases,69 although it is subclinical in most cases. Recurrent laryngeal nerve palsy, which presents with dysphonia, may occur in 2% to 30% of cases depending on whether clinical dysphonia or true vocal cord paralysis is considered the diagnostic measure.69 The risk of recurrent laryngeal nerve injury is increased with exposure below the level of C5 as well as with revision procedures. Superior laryngeal nerve injury is a rare occurrence and results in dysphagia and loss of high phonation. This structure is at greatest risk with approaches at the level of C3–C4. 
Horner’s syndrome also may occur, although infrequently, in the anterior cervical approach. The syndrome results from damage to the sympathetic plexus and stellate ganglion, which overlay the muscle belly of the longus colli. Injury can occur from retraction or direct damage from cautery if dissection is carried out over the longus colli. The condition classically presents with ptosis, meiosis, and hemianhydrosis. The high anterior cervical approaches can also potentially injure the hypoglossal, facial, and glossopharyngeal nerves. Peripheral nerve injury and/or radiculopathy are estimated to occur in 1% to 3% of cases, although this incidence is largely derived from experience with degenerative cervical conditions.69 A similar rate has been reported for dural tears in association with the anterior approach. However, the dura may already be disrupted as a result of the precipitating injury, rather than being caused during surgery. If the durotomy occurred as a result of trauma, it may be difficult to repair primarily using suture, necessitating adjuncts such as collagen matrices, polyethylene glycol hydrogel and fat, or myofascial grafting. 
If feasible, the authors prefer to use 5-0 or 6-0 prolene or neurilon sutures in a running, locked fashion to achieve watertight closure of a durotomy. The patient should be maintained in a seated position for 48 hours after the procedure, and a wound drain is not placed. An antibiotic that crosses the blood–brain barrier, such as ceftriaxone, is administered prophylactically for 24 to 48 hours or until wound drainage ceases. In the event of a persistent spinal fluid leak, a subarachnoid lumbar drain can be placed, but it is generally recommended that reexploration and revision repair be performed to limit the risk of meningitis and spinocutaneous fistula formation. 
Life-threatening complications may result from anterior cervical approaches, including damage to the vertebral artery or esophagus. The incidence of vertebral artery injury has been reported to be five per 1000 cases.46 The risk can be minimized by carefully assessing preoperative CT scans to look for an anomalous position, or tortuosity, of the artery, maintaining midline orientation while performing a corpectomy, and limiting the extent of decompression and exposure to the uncovertebral joints, particularly at the level of the disc space. 
Esophageal perforations present in 0.2% to 0.4% of cases.183 These injuries, especially if unrecognized, have a high associated mortality rate necessitating vigilance and a high index of suspicion among surgeons. A missed esophageal injury carries a 20% risk of mortality and the risk increases to 50% with the delay in treatment extending beyond 24 hours.183 The use of indigo carmine dye in an esophageal tube has not been found to be a reliable means of detection.69 If there is a high suspicion of esophageal injury, a thoracic surgeon should be consulted intraoperatively and the esophagus evaluated directly or endoscopically. Tears must be repaired primarily to diminish the risk of mediastinal infection. Large tears have necessitated the use of rotational sternocleidomastoid flaps to achieve cover. 

Complications Associated with the Posterior Approach

Immediate life-threatening complications, such as esophageal injury, are eliminated, for the most part, with the posterior approach, although the vertebral artery may still be at risk with approaches to the upper cervical spine and placement of lateral mass screws. There are also few complications specific to the posterior cervical approach itself. The risk of postoperative infection; wound problems, such as hematoma or dehiscence; pulmonary complications; and venous thromboembolic disease have been reported to be higher with a posterior approach relative to the anterior approach.29 There is also a greater risk of persistent CSF leak following durotomy with the posterior approach, because of the potential space created by the exposure as well as the absence of restrictive fascial planes. Because of this, myofascial grafts of flap cover may be needed to decrease the likelihood of persistent fluid leak or spinocutaneous fistulas. 
The insertion of lateral mass screws has generally been found to be safe, with a relatively low complication rate. The An technique may be associated with fewer neurovascular complications than the Magerl or Roy-Camille methods.139 In the largest review of consecutive lateral mass screws (1662 screws in 255 patients), Katonis et al.139 reported less than 1% rate of screw malposition. Lateral mass fracture occurred in 2%, whereas postoperative radiculopathy was encountered in 1% of patients. In a similar study involving 143 patients, Sekhon216 reported that no patients experienced neurovascular injuries as a result of screw placement. 

Perioperative Neurologic Deficit

In the immediate postoperative period, the most devastating event that can occur is a deteriorating, or new, neurologic deficit. If there has been no recognized intraoperative event, such as a direct spinal cord injury or posterior graft displacement, a careful and detailed examination should be performed by the same practitioner who had been serially examining the patient preoperatively. It should be determined whether the new deficit is above, at, or below the level(s) at which surgery was performed, and whether a nerve root or spinal cord injury is present. Plain radiographs of the operated region should be obtained first to see whether catastrophic failure of the construct has occurred. If a second, missed, noncontiguous spinal lesion is suspected, a full series of cervical, thoracic, and lumbar spine films should be obtained immediately. There should be little hesitation to obtain a postoperative CT or MRI scan. It is for this reason that the authors prefer to use titanium instrumentation, which is MRI-compatible. Screw, strut, and graft placement should be assessed to detect any impingement within the spinal canal, compression of nerve roots, or injury to the vertebral arteries. Hardware that appears to be a likely cause of neurologic deficit should be removed and/or repositioned in the operating room on an emergent basis. 

Early Postoperative Complications

Wound infection is one of the most common early postoperative complications, particularly following a posterior cervical approach.29 Infections following anterior surgery are rare and have not been found to exceed 1%,69 although the incidence may be somewhat higher in patients with a preexisting tracheostomy.179 
Superficial infections typically occur within the first 10 days after surgery and may be adequately treated with oral antibiotics and local wound care. If this is the chosen treatment, the wound should be closely monitored to ensure resolution. If the infection does not appear to be responding to treatment, as evidenced by increasing erythema, purulent drainage, or pain, early irrigation and debridement should be performed. Intraoperative cultures are important in determining the most appropriate antibiotic regimen, which can include up to 6 weeks of parenteral antibiotics. Well-fixed instrumentation and viable bone graft should be retained to maintain stability and promote eventual fusion. Aggressive, early surgical debridement of deep infections can help avoid late onset osteomyelitis, epidural abscess, meningitis, and catastrophic failure of instrumentation. 

Late Postoperative Complications

Pseudarthrosis and hardware failure are generally the most common late surgical complications. Symptomatic anterior pseudarthrosis can be treated with revision anterior surgery, but posterior instrumentation and fusion may be preferable. Early hardware failure can be associated with insufficiently stable constructs. Multilevel corpectomies stabilized with anterior fixation alone have a high rate of failure and should be routinely stabilized with posterior instrumentation and fusion.204,240 Anterior graft or plate extrusion can lead to swallowing difficulty, airway compromise, and even death. Late hardware failure, such as screw breakage, is often associated with nonunion, which may or may not be symptomatic. In certain instances, an asymptomatic fibrous union may not necessitate further treatment or revision surgery. 

Treatment Options for Specific Injuries for Cervical Spine Fractures and Dislocations

Occipitocervical Dislocation (C0–C1)

Mechanism of Injury

Occipitocervical dislocations are the result of high-energy distractive forces imparted to the occipitocervical junction. The relatively heavy cranium articulates tenuously with the mobile upper cervical region without an intervertebral disc and relies on the biomechanical properties of ligaments for restraint.147 Disruption of the ligamentous structures separates the occiput from C1, producing what is in reality a closed decapitation. Devastating traction injuries to the medulla oblongata and upper spinal cord often precipitate respiratory compromise and result in immediate death.127,147 Lador et al.147 documented occipitocervical dissociative injury in 14% to 18% of blunt trauma fatalities. Only slightly more than 100 patients have been documented as surviving these injuries in the entirety of the surgical literature.127 

Diagnosis and Classification

Because of the high associated risk of neural compromise and mortality, it is vitally important that occipitocervical dislocations are diagnosed as soon as possible in patients who survive the initial trauma.96,106,127,147 Because of their relative rarity, delayed diagnosis of these injuries is not unusual and can lead to catastrophic neurologic decline. In a review of 17 consecutive cases over an 8-year period, Bellabarba et al.21 documented that the diagnosis was made on the initial trauma plain film in only two patients. Moreover, there was, on average, a 2-day delay in diagnosis that resulted in secondary neurologic decline in 29% of the cohort. In a similar review, Govender et al.106 reported that two of four cases were initially missed on screening studies. It should be appreciated that plain radiographs were used in most of these studies as screening modality. The risk of missed occipitocervical injury is markedly reduced if computed tomography or MRI is used. 
Various means of evaluating the occipitocervical junction for injury have been proposed; however, the Basion-Axis Interval and the Basion-Dens Interval (Harris’ rule of 12) appear to be the most useful.37,127 Importantly, on radiographic review, some C1 or C2 injuries can functionally behave as an occipitocervical dissociation, such as the case reported by Jea et al.,131 in which an axially unstable Type III odontoid fracture with circumferential ligamentous instability occurred in a patient with brain stem dysfunction and quadriparesis. The equivalent of an occipitocervical dissociation can also occur through the atlantoaxial joint.254 
The system of classification proposed by Traynelis et al.234 remains the most commonly used. While the group of Bellabarba et al.21 postulated a new grading scale, intended to guide treatment, it has not been widely used. The Traynelis system is a descriptive classification, with Type I injuries showing anterior displacement of the occiput in relation to the C1 arch. Type II dislocations are axial separations of the occipitoatlantal junction, and Type III injuries exhibit posterior displacement (Fig. 44-34). Of note, a variant of Type II injury (classified as Type IIb) involves axial distraction through the C1–C2 articulation. 
Figure 44-34
Classification of occipitoatlantal dislocations.
 
Type I injuries exhibit anterior displacement of the occiput in relation to the C1 arch; type II have axial separation of the occipitoatlantal junction; and type III exhibit posterior displacement. Of note, a variant of type II (classified as type IIb) involves axial distraction through the atlantoaxial junction.
Type I injuries exhibit anterior displacement of the occiput in relation to the C1 arch; type II have axial separation of the occipitoatlantal junction; and type III exhibit posterior displacement. Of note, a variant of type II (classified as type IIb) involves axial distraction through the atlantoaxial junction.
View Original | Slide (.ppt)
Figure 44-34
Classification of occipitoatlantal dislocations.
Type I injuries exhibit anterior displacement of the occiput in relation to the C1 arch; type II have axial separation of the occipitoatlantal junction; and type III exhibit posterior displacement. Of note, a variant of type II (classified as type IIb) involves axial distraction through the atlantoaxial junction.
Type I injuries exhibit anterior displacement of the occiput in relation to the C1 arch; type II have axial separation of the occipitoatlantal junction; and type III exhibit posterior displacement. Of note, a variant of type II (classified as type IIb) involves axial distraction through the atlantoaxial junction.
View Original | Slide (.ppt)
X

Nonoperative Treatment

Indications

Most surgeons would agree that nonoperative treatment has little, if any, role in the definitive management of occipitocervical dislocations. Halo immobilization is most often used as a temporary means of stabilization, or a means of reducing injury, until surgery can be safely performed. Longitudinal traction is contraindicated in this setting. 

Results

In the past, successful treatment of patients, with distractive atlantoaxial injuries, in a halo vest has been reported, but the evidence is anecdotal and is unlikely to have any real value. Because of the high risk of neurologic deterioration in these injuries, as well as the high mortality rate, urgent surgical stabilization would appear to be the treatment of choice unless contraindicated for other reasons. 

Operative Treatment

Techniques of occipitocervical stabilization have improved dramatically with the advent of modern posterior instrumentation. Historically, the only fixation method available relied on the structural properties of iliac crest autograft that was fixed to the occiput, C1, and C2 with wires. As it was not rigid fixation, halo vest immobilization was routinely employed to confer additional stability. More recently, wiring contoured rods to the vertebrae provided more mechanical stability, but the fixation was insufficient to obviate the need for external immobilization. The introduction of plate and screw fixation was an immediate precursor to modern screw–rod systems. The so-called “Y” plate allowed screws to be inserted directly into the occiput, C1, and C2 and provided rigid internal fixation, although fatigue fracture was a common complication due to stresses across the occipitocervical junction. 
The current generation of occipital plates can be connected to polyaxial screws in the upper cervical spine and have been found to result in extremely stable and versatile constructs.73,101 Some systems allow independent insertion of an occipital plate and cervical screws, which are then connected using a contoured, or articulated, rod. While not technically possible with older fixation techniques that relied on hooks and wires, modern systems may even enable localized occipital–atlantal fixation via the use of C1 lateral mass screws as distal anchoring points, preserving atlantoaxial rotation.8 Similarly, Feiz-Erfan et al.91 reported success with isolated atlantoaxial fixation in a patient with Type IIb occipitocervical dislocation, presumably to preserve occipitocervical motion. Although good outcomes with these selective fusion techniques have been reported in specific instances, they remain technically demanding and require critical evaluation of the stability of the unfused C1–C2 or C0–C1 articulations. 

Indications

Surgical stabilization of occipitocervical dislocations should be considered the conservative treatment option. These injuries are grossly unstable, primarily ligamentous, and have little chance of healing with external immobilization alone. 

Results

Presently, no clinical evidence exists that documents the superiority of one method of occipitocervical fixation over another. Biomechanical data demonstrate that screw-based constructs are stronger than those that rely on hooks or wires.101 In one study, constructs using C2 pedicle screws, or C1–C2 transarticular screws, were stronger than those in which sublaminar wires or hooks were used for distal fixation.182 
In one of the first clinical studies to report the results of operative treatment of occipitocervical injuries using modern instrumentation, Bellabarba et al.21 had a 100% fusion rate in 17 patients followed for an average of 26 months. Overall, the average American Spinal Injury Association motor score for patients in this series improved from 50 to 79. Furthermore, the number of patients with an American Spinal Injury Association D or E grade increased from 7 preoperatively to 13 postoperatively. 
More recently, Horn and colleagues127 published their findings in a series of 33 patients who survived occipitocervical dislocations. The postoperative mortality rate was 22%, with those individuals having associated traumatic brain injuries found to have the highest risk of mortality. 

Authors’ Preferred Method of Treatment for Cervical Spine Fractures and Dislocations

 
 
Occipitocervical Dislocation
 

The authors’ preferred surgical treatment of occipitocervical dislocation is stabilization with an occipital plate and cervical screw–rod construct and fusion with iliac crest bone graft. Contemporary cervical instrumentation systems allow placement of an occipital plate using midline screws inserted into the thickest portion of the bone for maximal biomechanical strength.101,114,264 Lateral wings on the plate allow connection of an articulated rod from the occipital plate to C1 and/or C2 screws.

 
Preoperative Planning
 

Prior to surgery, careful inspection of preoperative images should be carried out. First, the direction of occipital dislocation should be noted, as this will determine the direction of reduction forces. A lateral radiograph of the skull, or ideally a sagittal CT scan of the head, should be used to measure the thickness of the occiput and location of the external occipital protuberance (inion). The inion is an important intraoperative landmark. In addition to having the thickest bone, it also demarcates the approximate level of the transverse sinus. Bicortical drilling can risk injury to this intracranial venous sinusoid, which can lead to intracranial hemorrhage. If magnetic resonance imaging is available, the transverse sinus can be directly visualized and its position relative to the inion noted. As a rule, screws should be kept distal to the inion whenever possible.

 

It is the authors’ preference to insert C2 isthmus (e.g., pars) screws as the distal fixation points. Sagittal CT scans must be inspected to ensure that the C2 pars is intact and of sufficient size to accept a 3.5-mm screw. The location of the vertebral artery foramen should also be noted, as this can affect the screw trajectory. With a low-riding vertebral artery foramen, the screw can be inserted parallel to the sagittal plane (Fig. 44-35). With a high-riding foramen, the screw must be kept short or angulated medially to avoid injury to the vertebral artery. This decision should be made preoperatively, as intraoperative fluoroscopic images are unlikely to allow adequate visualization of the foramen.

 
Figure 44-35
 
Careful inspection of a paramedian image through C2 reveals the bony corridor through which a screw can be placed (black arrow with dashed line). The vertebral artery in this patient is more high riding in its lateral course (right), while the artery is more inferior medially (left). This highlights the importance of preoperative imaging evaluation, as the screw trajectory should be medialized.
Careful inspection of a paramedian image through C2 reveals the bony corridor through which a screw can be placed (black arrow with dashed line). The vertebral artery in this patient is more high riding in its lateral course (right), while the artery is more inferior medially (left). This highlights the importance of preoperative imaging evaluation, as the screw trajectory should be medialized.
View Original | Slide (.ppt)
Figure 44-35
Careful inspection of a paramedian image through C2 reveals the bony corridor through which a screw can be placed (black arrow with dashed line). The vertebral artery in this patient is more high riding in its lateral course (right), while the artery is more inferior medially (left). This highlights the importance of preoperative imaging evaluation, as the screw trajectory should be medialized.
Careful inspection of a paramedian image through C2 reveals the bony corridor through which a screw can be placed (black arrow with dashed line). The vertebral artery in this patient is more high riding in its lateral course (right), while the artery is more inferior medially (left). This highlights the importance of preoperative imaging evaluation, as the screw trajectory should be medialized.
View Original | Slide (.ppt)
X
 
Positioning
 

If not already intubated, an endotracheal tube should be inserted using a fiberoptic scope173 to avoid unnecessary movement of the head and the neck. The head should be manually stabilized at all times.246 In the absence of a complete spinal cord injury, motor and sensory evoked potentials are monitored, with baseline signals obtained prior to transfer.246 Next, the patient is carefully logrolled into the prone position. A Jackson table–turning method can also be employed for transfer, as described by Rechtine’s group.72 Although more time-consuming, this technique has been shown to more effectively limit motion in unstable upper cervical spine injuries.

 

It is the authors’ preference to use a standard electric operating table with transverse chest rolls. Moving the head and the torso as a unit is paramount to avoid further displacement through the injury site. With all pressure points protected, the arms are tucked at the patient’s side and the knees flexed about 30 degrees. About 20 degrees of reverse Trendelenburg, with the head above the feet, can decrease venous congestion, which may reduce intraoperative blood loss. The head is positioned in a Proneview Helmet (Mizuho OSI, Union City, CA). No traction is applied.

 

A lateral fluoroscopic image should be obtained as soon as possible after prone positioning. Reduction of the occipital condyles within the superior articular surfaces of C1 must be confirmed. Gentle reduction maneuvers can be attempted to improve alignment, including an axial load placed on the head to reduce distraction. Finally, an AP view is obtained to ensure adequate visualization of the C1–C2 joint and the odontoid process, important landmarks for C2 screw insertion.

 
Approach
 

After sterile skin preparation and draping, a posterior midline approach is performed to expose a large portion of the occiput, the central 3 cm of the C1 ring, and C2 as described previously. Traumatic disruption of the dura is frequently encountered between the occiput and C1, or C1 and C2. These should be repaired with 5-0 neurilon suture, if possible, or sealed with a synthetic dural patch. Although it should not be violated, the C2–C3 facet joint must be included in the exposure, as it is an important guide for C2 screw insertion.

 
Technique
 

The first step in stabilization is placement of a sublaminar cable around C1. This enables better control of C1 during reduction. Following exposure of the posterior aspect of the C1 ring, a small-angled curette is used to subperiosteally dissect around the ventral aspect of the posterior C1 ring. After an adequate soft-tissue sleeve is created to buffer the spinal cord, the leader of a threaded double-loop cable is bent into a curve and passed around the C1 ring while maintaining contact with the bone. Because the interval between C1 and C2 is usually larger than the interval between the occiput and C1, it is the authors’ preference to pass the cable from proximal to distal. Care must be taken not to inadvertently push the leader into the spinal canal, and this risk can be minimized by keeping the cable against the ventral aspect of the posterior C1 ring. Once the leader loop is visualized in the C1–C2 interspace, it is retrieved using a small nerve hook. The cables are then pulled through, leaving equal portions above and below the C1 ring.

 

Starting holes for C2 isthmus screws are then made using a 2.5-mm high-speed burr. The location of the starting hole is just lateral and superior to the lateral aspect of the C2–C3 joint (Fig. 44-36). An AP odontoid view confirms that the starting points are aligned with the midaspect of the C1–C2 joint. Next, the C-arm is positioned for a lateral image. The proximal–distal location of the starting point should be adjusted so that it is centered within the midaspect of the C2 pars. A 2.5-mm drill bit (for a 3.5-mm screw) is advanced under manual control into the C2 pars. The tip of the drill bit should be directed toward the superior aspect of the pars to avoid the vertebral artery foramen on the lateral view. Provided adequate reduction and alignment can be maintained, a few degrees of capital flexion can help achieve the necessary angle.

 
Figure 44-36
 
The starting point (black dot) and trajectory (dashed arrow) for a C2 isthmus screw. The starting point lies just superior and lateral to the medial aspect of the C2–C3 joint.
The starting point (black dot) and trajectory (dashed arrow) for a C2 isthmus screw. The starting point lies just superior and lateral to the medial aspect of the C2–C3 joint.
View Original | Slide (.ppt)
Figure 44-36
The starting point (black dot) and trajectory (dashed arrow) for a C2 isthmus screw. The starting point lies just superior and lateral to the medial aspect of the C2–C3 joint.
The starting point (black dot) and trajectory (dashed arrow) for a C2 isthmus screw. The starting point lies just superior and lateral to the medial aspect of the C2–C3 joint.
View Original | Slide (.ppt)
X
 

Provided the patient has amenable anatomy as determined on preoperative CT scan, the drill can be maintained in a perfectly sagittal orientation or slightly medial. Lateral deviation puts the vertebral artery at risk. Overzealous medial angulation risks violation of the spinal canal. As the pars screw is unicortical, tactile feedback and fluoroscopy are important to prevent penetration of the anterior cortex. After the drill bit has been inserted to a sufficient depth, the hole is probed, measured, and tapped. The screw is then inserted under lateral fluoroscopic guidance. With both C2 screws in place, an AP view should confirm that they are directed toward the midaspect of the C1–C2 joint.

 

The next step is application of the occipital plate. The borders of the inion are noted. An appropriately sized plate can be trialed and proper positioning confirmed at the prospective location. Ideally, the plate should be placed so that the most proximal screw hole is as close to, but still inferior to, the inion. Using a marking pen, the site of the proximal screw is designated. The plate is then removed to allow easier preparation of the initial hole. The 2.5-mm burr is used to create a starting hole, followed by drilling with sequentially longer bits. Most systems provide a method to drill in controlled increments of 2 mm, starting at a depth of 6 mm. While bicortical screw fixation is strongest, unicortical fixation near the inion is safer and has acceptable biomechanical properties.114 It is the authors’ preference to predetermine the screw length on the basis of preoperative CT measurements. The hole is then tapped to the same depth. With the first occipital screw path prepared, the plate is then placed into position and provisionally held by screw insertion. The plate must be held in the ideal position, as it can rotate with screw tightening. This apical screw will hold the plate in a secure position while the other screws are inserted using a similar technique.

 

The authors prefer to use articulated rods to connect the plate to the C2 screws. After it is cut to an appropriate length, the rod is inserted into the tulip screw heads. Lock nuts are loosely inserted into the screw heads, while a final reduction is performed. Reduction relies on manipulation of the proximal and distal segments. A tonsil clamp can be used to grasp the occipital plate to control the head; a towel clip can be placed on the C2 spinous process for distal control. Alternatively, the sublaminar C1 cable can be used to deliver a posterior force. AP translation can be held in a corrected position while an assistant fixes the rods to the tulip heads with the lock nuts. A lateral view should confirm acceptable reduction of the condyles within the articular surfaces of C1. In a final step, minor adjustments in flexion–extension can be made through the rod articulations before they are final tightened.

 

A large piece of tricortical iliac crest bone graft is harvested. It is contoured to fit between the occipital base and the superior aspect of the C2 laminae and spinous process. Ideally, the bone graft should also contact the C1 ring. After decorticating the contact areas on the occiput, C1, and C2, the graft is held in place with the sublaminar cable (Fig. 44-37).

 
Figure 44-37
 
Magnetic resonance images of a patient with an occipitoatlantal dissociation (A) showing a frankly disrupted tectorial membrane (black lines) and resultant spinal cord compression. There was an increased interval noted between the basion (B) and odontoid (O). The patient had previously undergone an anterior corpectomy and fusion in the subaxial region. A posterior occipitocervical fusion was performed (B, C).
Magnetic resonance images of a patient with an occipitoatlantal dissociation (A) showing a frankly disrupted tectorial membrane (black lines) and resultant spinal cord compression. There was an increased interval noted between the basion (B) and odontoid (O). The patient had previously undergone an anterior corpectomy and fusion in the subaxial region. A posterior occipitocervical fusion was performed (B, C).
View Original | Slide (.ppt)
Figure 44-37
Magnetic resonance images of a patient with an occipitoatlantal dissociation (A) showing a frankly disrupted tectorial membrane (black lines) and resultant spinal cord compression. There was an increased interval noted between the basion (B) and odontoid (O). The patient had previously undergone an anterior corpectomy and fusion in the subaxial region. A posterior occipitocervical fusion was performed (B, C).
Magnetic resonance images of a patient with an occipitoatlantal dissociation (A) showing a frankly disrupted tectorial membrane (black lines) and resultant spinal cord compression. There was an increased interval noted between the basion (B) and odontoid (O). The patient had previously undergone an anterior corpectomy and fusion in the subaxial region. A posterior occipitocervical fusion was performed (B, C).
View Original | Slide (.ppt)
X
 
Postoperative Care
 

One of the main advantages of rigid occipitocervical fixation over earlier wire-based methods is that screw–rod techniques obviate the need for postoperative halo vest immobilization. However most postoperative patients are placed in a cervical collar. Wound and drain care is as described previously. AP, lateral, and open-mouth radiographs are obtained postoperatively. The patient is mobilized as tolerated. Follow-up radiographs are obtained at 2 weeks, 6 weeks, 3 months, 6 months, and annually thereafter to assess the integrity of the construct and fusion.

 
Pearls and Pitfalls
 

Malreduction of the occipital condyles on C1 can occur quite readily if proper precautions are not taken. Although sometimes challenging, the surgeon should be confident that he or she can adequately identify important bony landmarks on the lateral view, including the basion and odontoid tip. The tip of the odontoid should be in relatively close proximity to the basion before the final construct is locked into place. It is less reliable to judge AP translation by examining the relationship between the C1 ring and the occiput. However, a change in the relative position may be gauged by comparing preoperative and intraoperative images.

 

While bicortical occipital screws are stronger, they also are associated with a greater risk of dural penetration. If CSF is encountered during occipital hole preparation, bone wax can be used to control fluid escape. Ultimately, insertion of the screw effectively seals the leak.

 

Overtensioning of the cables can lead to fracture of the bone graft. In contrast to older techniques, modern spinal instrumentation systems do not rely upon the integrity of the bone graft for stability. If graft fracture does occur, the sublaminar cable can be removed and the graft repositioned to span the occiput to C1 and C1 to C2. An overlay cable, or heavy suture, can be passed around the rods, posterior to the graft to hold it in position.

 
Occipital Condyle Fractures
 
Mechanism of Injury
 

Occipital condyle fractures can occur from a variety of mechanisms. Stable fractures, such as Anderson Types I and II and Tuli Types 1 and 2A, probably occur from axial impaction of the head onto the cervical spine. Unstable injuries result from ligamentous disruption with associated avulsion fractures of the condyle and are probably caused by distraction between the head and the cervical spine.

 
Associated Injuries
 

Occipital condyle fractures can present with or without cranial nerve injuries97,171 and also may be associated with fractures in other locations within the cervical spine.105 Freeman and Behensky97 reported a case in which hypoglossal nerve palsy developed in the setting of bilateral occipital condyle fractures. Likewise, Urculo et al.237 treated a patient who developed glossopharyngeal and vagus nerve palsies that were not diagnosed until 4 months after sustaining an occipital condyle fracture. Chen et al.53 documented two cases of internal carotid artery dissection after isolated Type III occipital condyle fractures. Based on these findings, the authors recommended cerebral angiography in all patients with such injuries.

 
Diagnosis and Classification
 

CT is the imaging modality of choice for detecting these fractures, as plain radiographs can lead to missed injuries. Fracture fragment size, apposition, and gapping are best assessed on coronal and sagittal CT reconstructions. Radiographs are unreliable in demonstrating occipital condyle fractures.

 

A number of classification systems have been proposed to describe occipital condyle fractures.11,16,236 In a classic work, Anderson and Montesano11 used their experience with six patients, in addition to previously published findings, to develop a classification scheme for condyle fractures. In this classification, Type I injuries are impaction fractures, Type II injuries are basilar skull fractures that extend into the condyle, and Type III injuries are displaced avulsion fractures (Fig. 44-38). Type I and II fractures are the more stable variants, whereas Type III injuries tend to be associated with ligamentous disruption and are considered unstable. Accordingly, Anderson and Montesano11 recommended nonoperative treatment of Type I and II fractures, whereas occipitocervical stabilization and fusion was advocated for Type III fractures.

 
Figure 44-38
Classification of occipital condyle fractures.
 
Type I injuries are impaction fractures, type II injuries are basilar skull fractures that involve the condyle, and type III injuries are displaced avulsion fractures.
Type I injuries are impaction fractures, type II injuries are basilar skull fractures that involve the condyle, and type III injuries are displaced avulsion fractures.
View Original | Slide (.ppt)
Figure 44-38
Classification of occipital condyle fractures.
Type I injuries are impaction fractures, type II injuries are basilar skull fractures that involve the condyle, and type III injuries are displaced avulsion fractures.
Type I injuries are impaction fractures, type II injuries are basilar skull fractures that involve the condyle, and type III injuries are displaced avulsion fractures.
View Original | Slide (.ppt)
X
 

The Anderson classification scheme is encountered most frequently, although Tuli et al.236 also proposed a grading system for occipital condyle fractures on the basis of their review of 93 injuries. Stable, nondisplaced injuries were classified as Type 1, whereas displaced fractures without ligamentous injury were categorized as Type 2A. Type 2B fractures were displaced and associated with ligamentous disruption. It is essential to note that the Tuli scheme necessitates computed tomography and MRI in order to determine whether the injury is stable or unstable. In a recent series, Aulino et al.16 maintained that it was difficult to distinguish between Type 1 and 2A fractures using the Tuli classification.

 
Nonoperative Treatment
 
Indications
 

Most occipital condyle fractures can be treated nonoperatively. A rigid cervical collar worn for 8 to 12 weeks is usually sufficient for Anderson Type I and II injuries. Because of the potential for instability with Type III fractures, halo vest immobilization or operative treatment is indicated. Beyond the distinction between injury types in classification systems, the authors rely more heavily on inspection of the integrity of the tectorial membrane on MRI to differentiate stable from unstable variants. In the authors’ practice, disruption of the tectorial membrane as indicated by MRI is a relative contraindication for nonoperative treatment (Fig. 44-39).

 
Figure 44-39
MRI, magnetic resonance imaging.
View Original | Slide (.ppt)
Figure 44-39
Occipital condyle fracture treatment algorithm.
MRI, magnetic resonance imaging.
MRI, magnetic resonance imaging.
View Original | Slide (.ppt)
X
 
Results
 

Capuano et al.48 reported results of nonoperative treatment of occipital condyle fractures. There were five Type III, three Type II, and two Type I fractures. Successful healing was documented in all 10 patients.48

 
Operative Treatment
 
Indications
 

Operative treatment is indicated to treat unstable injuries. The authors’ criterion for instability is disruption of the tectorial membrane as assessed on sagittal T2-weighted magnetic resonance images. Using available classification systems, Anderson Type III and Tuli Type 2B fractures are described as unstable, although they are not always associated with tectorial membrane disruption. In cases that are functionally craniocervically unstable, occipitocervical stabilization and fusion is indicated (Fig. 44-39).

 
Results
 

The results of occipitocervical fusion for unstable occipital condyle fracture are similar to those documented for occipitocervical dislocations. In a series of patients with occipital condyle fractures, Hanson et al.115 reported good outcomes following occipitocervical fusion or halo vest immobilization in unstable injuries. Caroli et al.49 also maintained that successful healing occurred in five patients who were treated surgically for unstable occipital condyle fractures.

Authors’ Preferred Method of Treatment for Cervical Spine Fractures and Dislocations

 
 
Occipital Condyle Fractures
 

It is the authors’ practice to routinely evaluate occipital condyle fractures for associated ligamentous injury, or disruption of the tectorial membrane, using MRI. In the absence of ligamentous injury, stable occipital condyle fractures are immobilized in a rigid cervical collar or CTO for 8 to 12 weeks (Fig. 44-39). If MRI demonstrates ligamentous disruption or injury to the tectorial membrane, occipitocervical stabilization and fusion, as described perviously, is performed. Similarly, displaced fractures with ligamentous injury are treated with occipitocervical fusion. If the ligamentous structures are intact, displaced fractures can be managed with a halo vest, or CTO, for 12 weeks.

 
Complications
 

Isolated occipital condyle fractures can occur in the setting of occipitocervical ligamentous injury without substantial malalignment.27 Thus, a high index of suspicion for occult ligamentous injury must be maintained, regardless of the fracture type, until ligamentous disruption is ruled out by MRI. Caroli et al.49 recognized the potential for occult instability in association with occipital condyle fractures, and other authors237 have highlighted the potential for concomitant cranial nerve injury.

 
Atlas Fractures (C1)
 
Mechanism of Injury
 

C1 fractures can occur through a variety of mechanisms. Simple posterior ring fractures are thought to occur from hyperextension, as the C1 ring can be impinged between the occiput and C2. The mechanism of injury with Jefferson (burst) fractures is generally presumed to be axial load that results in failure of the C1 ring. However alternative mechanisms have also been suggested, however. In a biomechanical study on human specimens, Beckner et al.20 found that pure lateral tensile loads can result in similar fracture patterns. Although spinal cord injury is infrequently associated with isolated injuries, unstable fractures from high-energy mechanisms may carry a greater risk. Vertebral artery occlusion, although rare, has been reported in association with Jefferson fractures.175

 
Diagnosis and Classification
 

Various fracture patterns present within the C1 vertebra. First, it is not mechanically possible to fracture the C1 ring in only one location and the minimum number of fracture sites is two. Posterior arch fractures are the simplest and most benign pattern, with two fractures in the C1 ring occurring posterior to the lateral masses. While these have little mechanical significance regarding spinal stability, their recognition is important if C1 sublaminar wiring is planned for the treatment of other associated fractures.

 

The classic Jefferson fracture pattern has bilateral fractures in the anterior and posterior aspects of the ring. However, the mechanical significance of a single burst fracture in the anterior and posterior ring is the same. As long as the left and right sides of the ring have been dissociated, the potential for injury to the C1–C2 facet joint and the transverse ligament is present. The exact location of the fractures can vary substantially, with some injuries extending into the lateral masses.

 

The distinction between stable and unstable burst fractures is the integrity of the transverse ligament. The transverse ligament is disrupted in tension with lateral displacement of the fragments, resulting in C1–C2 instability. An intact ligament, spanning the lateral masses and the odontoid, functions as a soft-tissue restraint that limits the degree of displacement. Apart from direct inspection on MRI, which can be difficult and potentially unreliable, the integrity of the transverse ligament is usually based on the amount of lateral overhang of the C1 lateral masses on C2. As detailed in the section on radiographic injury detection, this measurement is made on the open-mouth view. Combined left and right lateral mass overhang on C2 exceeding 7 or 8 mm implies transverse ligament injury.

 
Nonoperative Treatment
 
Indications
 

Treatment of Jefferson, C1 burst, fractures has varied over time. However, in the absence of more serious cervical injuries, most surgeons advocate nonoperative treatment in the vast majority of cases. Isolated C1 ring fractures might require formal immobilization for only a short period of time, provided that adequate flexion–extension views do not demonstrate instability. Stable burst fractures can be treated nonoperatively in a rigid cervical collar for 8 to 12 weeks. Unstable fractures may be reduced in halo traction and definitively treated in a halo vest for 12 weeks. Importantly, flexion–extension views should be obtained after the fracture has healed to rule out residual C1–C2 instability.

 
Results
 

Traction can successfully reduce displaced C1 fracture fragments and maintain alignment until the fractures heal. Lee et al.150 retrospectively reviewed the results of nonoperative management with a rigid cervical collar in 16 patients with stable Jefferson fractures. No C1–C2 instability was evident at 1-year follow-up and all individuals appeared to heal their injuries.

 
Posterior Surgery
 

Posterior atlantoaxial stabilization and fusion is an effective treatment of residual C1–C2 instability following C1 burst fractures. In the acute setting, methods that rely on C1 sublaminar cables or wires, such as Brooks or Gallie techniques, are not technically feasible, because the fracture involves the posterior arch. If the ring fracture has sufficiently healed, wiring methods can be performed later. Screw fixation has been advocated as a superior method of treating acute C1 fractures, as it does not rely on the integrity of the C1 arch. Provided that an adequate fracture reduction can be achieved, transarticular C1–C2 screws may be used for stabilization. These constructs have superior control over fracture fragments in all motion planes as compared with wire-based techniques. If preferred, or if adequate reduction cannot be obtained, C1 lateral mass116 and C2 instrumentation can be used, including C2 pedicle screws, pars screws, or intralaminar screws.73 A recent biomechanical study by Dmitriev et al.73 postulated that, for atlantoaxial fixation for fracture, C2 pedicle screws provided the greatest biomechanical integrity, followed by intralaminar screws and then pars fixation.

 
Indications
 

Surgical stabilization has a role in select cases, often after the failure of nonoperative measures, or concomitant disruption of the transverse ligament.

 
Results
 

Hein et al.125 demonstrated that atlantoaxial stabilization and fusion using transarticular screws was successful for acute, or subacute, Jefferson-type fractures. In this series, solid fracture healing was reported in all cases at the time of final follow-up. Dvorak et al.79 followed a larger series of patients with Jefferson fractures for a period of 75 months. Importantly, in this study, the authors found that even after satisfactory healing, few patients return to their preinjury state of health or approximated the mean scores of age-matched controls. Ligamentous disruption and instability were identified as indicators of poor outcome regardless of treatment.79

 
Anterior Surgery
 
Indications
 

Although not popular, some have advocated anterior osteosynthesis of the C1 ring following fracture. The exact indications for this technique are unclear, as it does not directly address transverse ligament disruption.

 
Results
 

Ruf et al.200 reported the use of anterior osteosynthesis of the C1 ring to treat Jefferson fractures through a transoral approach. It is unclear, however, how this treatment would address residual C1–C2 instability from transverse ligament disruption.

Authors’ Preferred Method of Treatment for Cervical Spine Fractures and Dislocations

 
 
Isolated C1 Ring Fractures
 

The authors prefer to treat isolated C1 ring fractures nonoperatively in patients who are neurologically intact (Fig. 44-40). For simple posterior arch fractures, a hard collar is worn for 2 to 4 weeks. Flexion–extension views are then obtained to confirm mechanical stability of the spine. For burst and Jefferson fractures with less than 7 to 8 mm of lateral overhang on open-mouth odontoid views, a rigid cervical collar, or CTO, is worn for 12 weeks. Although a confirmative CT scan is not routinely obtained, adequate fracture healing is presumed to be present at this time. Flexion–extension views are then obtained to rule out occult C1–C2 instability.

 
Rockwood-ch044-image040.png
View Original | Slide (.ppt)
Figure 44-40
C1 fracture treatment algorithm.
Rockwood-ch044-image040.png
View Original | Slide (.ppt)
X
 
Traction and Halo Vest Immobilization
 

Burst or Jefferson fractures with more than 7 to 8 mm of lateral overhang are presumed to be unstable. In the authors’ practice, unstable injuries in patients without neurologic deficit are treated first with longitudinal traction delivered via a halo ring. An open-mouth view is obtained to confirm adequate reduction. Following a short period of sustained traction of 3 to 5 days, the patient is then placed in a halo vest and mobilized. Importantly, traction is maintained until the vest is secured. Before releasing the traction, the wheel nuts on all four of the upright struts are maximally lengthened to pretension the unit.

 

Once the patient is upright, a repeat open-mouth view is obtained. While some mild displacement due to axial settling is expected, excessive (>5 or 6 mm) loss of reduction is suboptimal. If this occurs, the patient may be considered to be a candidate for posterior atlantoaxial instrumented fusion, as detailed in the section on treatment of atlantoaxial instability. This may also be necessary if neurologic deficits do not resolve with realignment after halo traction.

 
Complications
 

C1–C2 instability is a well-recognized sequela following Jefferson C1 burst fractures and thus should be considered a true complication. Instability results from transverse ligament disruption, which, by itself, has been demonstrated to allow a maximum of 5 mm of widening at the ADI. The alar ligaments are usually not disrupted with Jefferson fractures, as the odontoid process is not displaced relative to the anterior foramen magnum, where the ligaments insert. Once the C1 ring fractures have healed, and assuming that no concomitant cervical fractures are present, the injury should be treated as atlantoaxial instability (see later).51 Greater than 5 mm of widening of the ADI implies a more substantial, and potentially dangerous, degree of instability that places the spinal cord at risk. In such cases, a C1–C2 fusion using C1 lateral mass and C2 isthmus screws is performed as described later.

 
Sagittal Atlantoaxial Instability without Fracture (C1–C2)
 
Mechanism of Injury
 

Sagittal instability of the atlantoaxial junction most likely occurs from an abrupt flexion moment that results in shear forces acting on the C1–C2 articulation. Instability results from a ligamentous injury that, at minimum, involves the C1–C2 facet capsules and the transverse ligament with or without alar ligament disruption. Anatomical studies suggest that transection of the transverse ligament alone allows widening of the ADI to a maximum of 5 mm, with the alar ligaments preventing further displacement.93,222 Disruption of the alar ligament ultimately allows ADIs that exceed 5 mm. Distraction injuries through the atlantoaxial joint, and instability following atlas fractures, are considered elsewhere in this chapter, as they have distinctly different mechanisms of injury and treatment modalities.

 
Diagnosis and Classification
 

The diagnosis of this injury can typically be made on plain radiographs by measuring the ADI.255 Normally, this interval is no greater than 2 to 3 mm in adults. In an awake, cooperative patient who is neurologically intact, flexion–extension images in a controlled setting can be obtained to detect occult instability in a patient with a normal ADI. Flexion–extension films may not be necessary in a patient with a grossly widened (>5 mm) ADI, as disruption of both the alar and transverse ligaments can be inferred. For those with initial ADIs that are somewhat widened (3 to 5 mm), or asymmetrical (e.g., angulation of the C1 ring on the odontoid peg results in a wide ADI superiorly but normal ADI inferiorly), flexion–extension views can be useful in distinguishing the degree of instability.

 

As CT scanning is quickly supplanting plain radiographs for the initial trauma survey, one should be comfortable assessing the ADI on sagittal and axial images.37 An axial view through the C1 ring or a midsagittal reconstruction can be used to measure the ADI. MRI is not useful for ADI measurement, as osseous contours are often difficult to discern. However, high-quality axial images can be used to directly inspect the contiguity of the transverse ligament, whereas sagittal and coronal images display the alar ligaments. Increased signal within the C1–C2 facet joint or between the atlas and odontoid process may also be suggestive of injury.

 
Nonoperative Treatment
 
Indications
 

The determination of the optimal treatment modality is case-specific and depends on the magnitude of instability, the presence of neurologic compromise, and patient age. Isolated transverse ligament injuries usually do not result in gross instability. In a patient who is neurologically intact, nonoperative treatment in a collar or a halo vest can be used, provided the ADI can be held in a reduced position. The transverse ligament can heal, particularly if it is attached to a small avulsion fracture. Younger patients have a greater chance of healing. Nonoperative management is usually contraindicated in patients with ADIs greater than 5 mm, spinal cord injury, or in patients in whom a concomitant injury (e.g., pulmonary injury, cranial fracture) may preclude safe halo-thoracic immobilization.

 

As an adjunct to both operative or nonoperative management, traction can be an effective method of reducing sagittal C1-C2 instability. The traction force vector should be directed slightly posteriorly, so, if cranial tongs are used, the pins must be located just anterior to the external auditory meatus. Importantly, care must be taken to rule out axial instability after the initial placement of 5 to 10 lb. Although the only initial radiographic abnormality may be a widened ADI, circumferential ligamentous C1–C2 disruption behaves functionally as a craniocervical dissociation that can exhibit substantial, and potentially dangerous, axial displacement with even low amounts of traction weight.38

 
Results
 

Nonoperative treatment may be effective in selected cases, such as isolated transverse ligament disruption in a neurologically intact, low-demand, elderly individual. In general, surgical treatment via C1–C2 stabilization and fusion is advocated.

 
Operative Treatment
 

Surgical treatment of sagittal C1–C2 instability without fracture usually consists of posterior atlantoaxial stabilization and fusion.130 A variety of methods have proven effective over time, including Gallie or Brooks techniques, transarticular screws, C1 lateral mass and C2 screws, or combinations thereof.

 
Indications
 

If a patient has an associated spinal cord injury, surgical treatment should be strongly considered regardless of the degree of instability. Patients with ADIs greater than 5 mm should also undergo C1–C2 fusion. Symptoms such as occipital headaches, neck pain, or C2 neuralgia in conjunction with late instability are also indications for surgical stabilization.

 
Results
 

Most series investigating the surgical treatment of C1–C2 instability have included patients with disparate types of injuries. At the present time, a dedicated review detailing outcomes of one or more surgical techniques exclusive to the treatment of pure ligamentous disruption at C1–C2 is not available. Overall, fusion rates appear to be highest with more stable methods of fixation, such as C1 lateral mass C2 instrumentation or C1–C2 transarticular screw stabilization. The classic wire-based constructs, such as Gallie or Brooks techniques, are less effective at providing immediate stability to the injured segments.44,100,132

Authors’ Preferred Method of Treatment for Cervical Spine Fractures and Dislocations

 
 
Sagittal Atlantoaxial Instability
 

The authors prefer to treat most cases of sagittal atlantoaxial instability surgically with posterior stabilization using C1 lateral mass and C2 isthmus screws, followed by fusion with tricortical iliac crest autograft.

 
Preoperative Planning
 

A CT scan should be examined to note the location of the vertebral artery foramen at C2 and estimate screw trajectory and length. The proximity of the internal carotid artery to the anterior aspect of C1 should also be noted on axial MRI sequences, as this structure can be endangered with bicortical C1 lateral mass screws.

 
Positioning
 

After fiberoptic intubation and baseline motor and sensory evoked potentials have been obtained, the patient is positioned prone on a standard electric operating table. Reduction of the C1–C2 joint can be achieved and maintained by neck extension and gentle traction attached to the head of the table.

 
Approach
 

A standard midline approach is used to expose the posterior C1 ring along its central 3 cm and the C2 laminae and spinous processes. The C2 isthmic screws are placed before exposure of the C1–C2 joints and C1 lateral masses, which may be associated with increased blood loss due to disruption of the venous plexus surrounding these structures. Bipolar cautery is used to dissect superiorly along the posterior cortical surface of the C2 pars/pedicle until the C2 nerve root is encountered. This is retracted inferiorly, allowing exposure of the C1 lateral mass. At no time should dissection proceed above the C1 ring along its lateral aspect because of risk of injury to the vertebral artery. In the authors’ preferred technique, the posterior C1 arch is not used as a landmark for screw insertion.

 
Technique
 

A double-looped cable is passed around the C1 posterior arch. A posterior force on this cable anchor allows excellent control of the ring and complete reduction of the ADI. C2 isthmus screws are then inserted under fluoroscopic guidance as described earlier in the section entitled Occipitocervical Dislocations. Importantly, this is performed prior to exposure of the C1 lateral masses for two reasons. First, the dissection usually involves entry into an epidural or epineural venous plexus, where complete hemostasis may be difficult. Since placement of the C2 screw does not require exposure of this region, insertion is performed first to minimize total blood loss. Second, a well-placed C2 isthmus screw can be used as a medial–lateral landmark for the C1 screw starting point. As mentioned previously, a C2 screw is ideally directed toward the midaspect of the C1–C2 articulation.

 

The entry point for the C1 screw is located inferior to the C1 posterior arch, within the midaspect of the lateral mass. Provided adequate exposure of the posterior cortical surface has been achieved, a Penfield elevator can be used to retract the C2 nerve root inferiorly. The C1–C2 articular surfaces can usually be clearly seen, as the joint capsule has been disrupted by the trauma. A lateral view is used to confirm that the Penfield is resting along the posterior margin of the lateral mass. A 2.5-mm burr is then used to create a starting hole, followed by preparation of the screw path with a 2.5-mm drill bit under hand power. The bit is angled medially about 10 degrees to access the thicker bone in this region. It is the authors’ preference not to penetrate the far cortex.

 

Judging screw length can be challenging, as the majority of the screw shaft will lie outside the bone. A depth gauge is inserted. However, instead of measuring the intraosseous path, the depth gauge is adjusted to be aligned with the tulip head of the C2 screw. Most systems have long, terminally threaded, screws with smooth proximal shanks to avoid irritation of the C2 nerve root. The appropriate-length screw is inserted and its position confirmed on AP and lateral fluoroscopic views. Rods are then cut to the appropriate length and loosely affixed to the screw heads on either side. To ensure complete reduction, the C1 cable can be used to pull the C1 ring posteriorly while an assistant tightens the locking nuts. A lateral view should confirm reduction with traction removed. A tricortical piece of iliac crest autograft is then cabled in place over the decorticated posterior surfaces of C1 and C2.

 
Postoperative Care
 

Although this technique provides rigid internal fixation, it is the authors’ practice to maintain the patient in a hard cervical collar for 8 to 12 weeks. If the patient has multiple injuries and will be in the intensive care unit for a prolonged period, the collar can be removed.

 
Pearls and Pitfalls
 

Incomplete reduction of the ADI is best avoided by achieving a nearly perfect reduction prior to incision. Intraoperatively, reduction is aided by the C1 sublaminar cable. The surgeon must ensure, however, that the C1 ring is intact and that a nondisplaced odontoid fracture is not present. Aggressive force on the C1 cable can lead to displacement of these unrecognized injuries.

 
Complications
 

Complications of the surgical technique include wound infection, blood loss from the epidural plexus, dural tear, neurologic deterioration, and pseudarthrosis. Complications specific to the surgical treatment of this injury include malreduction and overdistraction of the C1–C2 joint from aggressive intraoperative manipulation.

 
Atlantoaxial Rotatory Dislocation (C1–C2)
 
Mechanism of Injury
 

Isolated, traumatic atlantoaxial rotatory dislocation is rare in adults, with few series reporting the incidence or outcomes of this injury. Lukhele159 reported results of a series of 10 patients with atlantoaxial rotatory dislocation caused by trauma or infection. Traumatic injuries most likely occur from a combination of lateral flexion (LF) and forced rotation. Patients who were diagnosed early in this series were effectively treated with traction and external immobilization. Surgical treatment, including occipitocervical fusion, was performed in those with delayed presentation. Rotatory dislocation in the setting of a displaced odontoid fracture has also been reported.99

 
Associated Injuries
 

One group has reported an association between C1–C2 rotatory instability and clavicle fractures.202 These authors postulated that the neck injury occurred during shoulder impact after a fall. While the clavicle injuries were detected acutely, identification of rotatory instability was delayed, resulting in a fixed deformity. Neurologic compromise is uncommon following C1–C2 rotatory injuries, although occipital neuralgia is more likely to be present.94

 
Diagnosis and Classification
 

Rotatory dislocations of the C1–C2 joint are a commonly missed injury. Lukhele159 showed that the delay in diagnosis ranged from 4 weeks to 2½ years. Asymmetry of the C1–C2 joints on an initial trauma CT scan is usually attributed to head posture during the examination, although such a finding may be indicative of rotatory injury. Barring other injuries that may preclude such an investigation, axial CT scans through C1–C2, obtained with the head maximally rotated to the left and right, will definitively demonstrate a fixed rotatory subluxation or dislocation. MRI may be used as an adjunct to identify increased edema at the C1–C2 articulation, or ligamentous disruption, although such findings can be nonspecific.

 

The classification system proposed by Fielding and Hawkins94 denotes four injury types. Type I is a rotatory deformity without widening between the odontoid process and the anterior C1 arch. Type II consists of widening in the range of 3 to 5 mm, implying transverse ligament disruption. Type III injuries have widening measuring more than 5 mm, indicative of transverse and alar ligament disruption. A Type IV injury has also been described, representing posteriorly translated rotatory dislocation. However, this pattern appeared only once in the series of Fielding and Hawkins,94 and the patient had rheumatoid arthritis that resulted in erosion of the odontoid. Posterior rotatory dislocation of the C1 ring over the odontoid process may functionally be more akin to a traumatic occipitocervical dissociation.

 
Nonoperative Treatment
 
Indications
 

Atlantoaxial rotatory dislocations that present in the acute period may be successfully managed nonoperatively. Reduction is achieved via traction and is usually successful.94 Once reduction is achieved, a decision must be made regarding the method of immobilization, which can vary from cervical orthosis to halo-thoracic vest. Wetzel and La Rocca255 recommended a cervical collar for Type I injuries, a CTO for Type II injuries, and halo vest for Type III injuries.

 
Results
 

The few series documenting the results of nonoperative treatment of rotatory instability consist of primarily pediatric patients with postinfection lesions. In these reports, nonoperative treatment is generally successful, provided a reduction can be achieved and maintained. The duration of immobilization after reduction has varied from 6 weeks to 3 months.94,255

 
Operative Treatment
 
Indications
 

Surgical treatment is indicated in cases associated with a spinal cord injury, gross dynamic instability (as detected on rotational CT scan), and in those patients in whom nonoperative measures have failed. It is unclear whether the results of pediatric patients whose instability occurred after infection can be applied to the adult patient with posttraumatic ligamentous injuries. In the setting of traumatic rotatory dislocations, a strong case for instrumented fusion can be made, even in the patient who is neurologically intact.

 
Results
 

Surgical treatment is most often posterior stabilization and fusion. The relative benefits, disadvantages, and results of the various techniques of posterior atlantoaxial fusion are described elsewhere in this chapter.

Authors’ Preferred Method of Treatment for Cervical Spine Fractures and Dislocations

 
 
Atlantoaxial Rotatory Dislocation (C1–C2)
 

The authors’ preferred approach to treatment for these rare injuries is usually instrumented fusion. Regardless of the severity, closed reduction with cranial tong traction is attempted. If reduction is successful, then posterior C1–C2 fusion is performed using C1 lateral mass C2 isthmus screws and iliac crest bone graft. If reduction cannot be achieved, open reduction of C1 and C2 is performed through a posterior approach, followed by instrumentation and fusion.

 
Odontoid Fractures (C2)
 
Mechanism of Injury
 

The mechanism of injury that produces odontoid fractures has not adequately been defined. In a biomechanical study using cadaveric specimens, Doherty et al.74 concluded that Type II odontoid fractures are likely caused by lateral or oblique forces, whereas Type III fractures resulted from extension mechanisms. While these injuries were previously well recognized in young patients injured in high-energy mechanisms, they are also increasingly encountered as isolated injuries in elderly patients following low-velocity falls.111,160,211

 
Associated Injuries
 

There are a numerous associated injuries that may occur from the traumatic forces sufficient to cause odontoid fractures. In the elderly, forehead lacerations and periocular ecchymosis are commonplace, as the usual mechanism is a frontal impact that causes neck hyperextension.

 
Diagnosis and Classification
 

The Anderson and D’Alonzo classification9 remains the most accepted method of describing odontoid fractures. In this system, Type I fractures are avulsion injuries involving the tip of the odontoid. Type II fractures occur at the junction of the odontoid process and the body of C2, and Type III fractures involve or extend into the vertebral body of C2 (Fig. 44-41). The system is purely descriptive and is incapable of defining treatment or predicting outcomes.

 
Figure 44-41
Anderson and D’Alonzo classification system for odontoid fractures.
 
Type I fractures are small avulsion fractures from the tip of the dens. Type II fractures occur through the so-called waist of the odontoid process. Type III fractures occur through the cancellous bone of the C2 vertebral body.
Type I fractures are small avulsion fractures from the tip of the dens. Type II fractures occur through the so-called waist of the odontoid process. Type III fractures occur through the cancellous bone of the C2 vertebral body.
View Original | Slide (.ppt)
Figure 44-41
Anderson and D’Alonzo classification system for odontoid fractures.
Type I fractures are small avulsion fractures from the tip of the dens. Type II fractures occur through the so-called waist of the odontoid process. Type III fractures occur through the cancellous bone of the C2 vertebral body.
Type I fractures are small avulsion fractures from the tip of the dens. Type II fractures occur through the so-called waist of the odontoid process. Type III fractures occur through the cancellous bone of the C2 vertebral body.
View Original | Slide (.ppt)
X
 

A clarification of the Anderson scheme has been suggested by Grauer et al,109 who maintained that the true distinction between Type II and III fractures lies in extension of the fracture into the superior articular surface of C2. Grauer and colleagues also subclassified Type II injuries on the basis of fracture obliquity, displacement, and comminution, factors generally believed to impact treatment decision making and outcomes. Type IIa fractures are transverse in orientation and minimally displaced. Type IIb injuries extend from the anterosuperior cortex in a posterior–inferior direction, and IIc fractures begin anteroinferiorly and extend posterosuperiorly. It is felt that Type IIb fractures are the ideal pattern for anterior osteosynthesis using odontoid screw fixation, and this may be the main use of the subclassification system.128 While Grauer et al.109 reported reasonable reproducibility among seven spine surgeons in a series of 52 cases, the system has not been clinically validated in an independent setting.

 
Nonoperative Treatment
 

Nonoperative treatment is probably the appropriate treatment of most odontoid fractures.160 Nonoperative management of odontoid fractures includes the use of an external orthosis, CTO, or a halo-thoracic vest.

 
Indications
 

A hard collar should be considered a method of symptomatic treatment for low-demand, elderly patients with nondisplaced odontoid fractures. A rigid cervical collar can be used to treat any nondisplaced fracture of the odontoid, regardless of its Anderson Type.160 Some believe that a halo vest is more appropriate for nondisplaced Type II fractures because of the reported high nonunion rate. Although a halo vest can be used to achieve and maintain a reduction in displaced Type II and III fractures, healing rates have not been found to be substantially higher than those associated with cervical orthoses.128

 
Results
 

Greene et al.111 reviewed the results of 340 patients with C2 injuries, which included both odontoid and hangman’s fractures. Their treatment algorithm included nonoperative management in all cases except in those patients in whom fracture alignment could not be maintained by an external orthosis, where there was an odontoid fracture associated with a transverse ligament disruption, a Type II odontoid fracture with displacement greater than 6 mm, or a high-grade hangman’s fractures. In this series, Type II odontoid fractures were found to have a nonunion rate that approached 30%.

 

Depending on the heterogeneity of the population under study, as well as treatment indications and the types of fractures, disparate studies show varying degrees of success with regard to external immobilization of odontoid fractures. Type III fractures typically fare better in external orthoses than do Type II injuries, unless the Type II fractures are nondisplaced.59,128 Koech et al.141 reported that 50% of Type II odontoid fractures demonstrated osseous union in elderly patients, although radiographic stability was found in 90%. Muller and colleagues174 documented 74% union among Type II odontoid fractures treated with external orthoses. In this series, criteria for external immobilization included fracture displacement less than 5 mm, separation between fracture fragments less than 2 mm, and angulation less than 11 degrees. Similarly, in a more recent series, Chaudhary et al.52 maintained that stability was achieved in all elderly patients treated with a cervical collar for Type II odontoid fractures. While the union rate was higher in those treated surgically, so was the mortality rate and mean postoperative pain score.

 
Traction and Reduction
 
Indications
 

Traction and reduction is an effective means of reducing displaced or angulated odontoid fractures. This method can be used as a prelude to either operative or nonoperative management. Traction and reduction can also be employed in patients with, or without, neurologic injury. Contraindications to traction include evidence of occipitocervical dislocation or cranial fractures at the proposed pin sites of a halo ring or tongs.

 
Results
 

Traction has been shown to be a safe and effective means of achieving closed reduction and realignment of odontoid fractures. In a retrospective series, Rushton et al.201 described a technique of bivector traction that allowed correction of both angular and translational deformity in posteriorly displaced fractures. Care must be taken when using traction in the acutely traumatized spine. In cases of unrecognized, occult occipitocervical dissociations that occur concomitantly with noncontiguous cervical fractures, inadvertent overdistraction of the craniocervical junction can occur.133

 
Halo Vest Immobilization
 
Indications
 

Halo vest immobilization was commonly used in the past as the standard treatment of displaced and nondisplaced Type II and III odontoid fractures. Traction via a halo ring may be initially used to reduce the fracture and then subsequently convert to a halo-thoracic vest. Halo vest immobilization may not be ideal in patients with fractures that cannot be reduced, or if a reduction cannot be maintained.

 
Results
 

Several historical works have documented satisfactory outcomes for odontoid fractures immobilized with halo-thoracic devices. However, none of these are level I evidence and most are retrospective studies comprising heterogeneous populations. Once again, union rates are higher for Type III fractures treated with halo-thoracic immobilization than for Type II injuries. Clark and White59 documented 87% healing for Type III odontoid fractures treated with a halo, and this figure approached 100% in the work of Greene et al.111 In their series, Clark and White59 found only a 66% union rate for Type II odontoid fractures immobilized in a halo, and in the series of Koivikko and colleagues,142 healing occurred in less than 50%.

 

Presently, there is a general concern that the use of halo vest immobilization in elderly patients can significantly increase the risk of postinjury mortality. The use of a halo-thoracic vest has been shown to increase swallowing difficulty,3 with an associated risk of aspiration in elderly patients.230 Similarly, the potential for pneumonia and cardiac arrest also appears to be elevated in geriatric patients following halo-thoracic immobilization.161,230 For example, in the work of Tashjian et al.,230 mortality and complication rates were significantly elevated in elderly patients treated with halo vest as compared with those immobilized in a cervical collar or receiving surgery. In this study, within the halo-thoracic cohort, the mortality and complication rates approached 50% and 70%, respectively. It is important to recognize, however, that other works focusing on elderly patients with odontoid fractures have not found a significantly increased risk of mortality with halo treatment as compared with other modalities.123,141,211

 
Operative Treatment
 

There are several different surgical treatments of odontoid fractures, with no demonstrable superiority of one technique over another. Options include osteosynthesis with an anterior odontoid screw, posterior C1–C2 fusion, and anterior C1–C2 fusion. Each technique carries a different set of advantages and associated complications. Ideally, should patient and fracture characteristics allow more than one treatment option, a frank discussion with the patients and their family regarding outcomes, postinjury expectations, and goals should be had to facilitate a shared decision-making process.

 
Indications
 

General indications for surgical treatment of an odontoid fracture in a younger patient include fracture displacement greater than 5 mm, fracture angulation greater than 10 degrees, neurologic deficit, substantial comminution, or multisystem trauma where external immobilization may not be well tolerated. The indications for operative treatment in elderly patients (older than 65 to 70 years) are less clear, as it appears that nonoperative management of some displaced fractures can yield satisfactory outcome in low-demand individuals, provided there is ample space available for the spinal cord and the patient is neurologically intact.123,211 Others propose more aggressive indications, recommending surgery for the majority of odontoid fractures in elderly patients.

 
Results
 

Surgical results for odontoid fractures vary according to technique. The results of individual operative methods are discussed below.

 
Anterior Odontoid Screw
 
Indications
 

Beyond the general surgical indications outlined earlier, anterior odontoid screw fixation requires additional considerations. With respect to fracture morphology, transverse fractures or oblique fractures in which the fracture line runs from anterosuperior to posteroinferior can be stabilized by an odontoid screw. However, odontoid screws are contraindicated in fractures that run from anteroinferior to posterosuperior (Grauer IIc), as compression will increase fracture displacement. Near anatomical reduction is required for odontoid screw insertion. As screw trajectory is a critical factor, screw insertion may not be technically feasible in patients with barrel-shaped chests or a pronounced cervical kyphosis. Patel et al.189 proposed that age greater than 65 years was a relative contraindication to odontoid screw fixation due to relative osteopenia and an associated increased risk of screw cutout. Odontoid screws are most appropriate for Type II fractures. They should not be considered for Type I and most Type III fractures, although some Type III fractures that pass through the superior aspect of the C2 vertebral body (closer to the odontoid waist) may be amenable to screw fixation.

 
Results
 

The published outcomes of anterior screw fixation vary. Alfieri4 claimed successful stabilization in nine cases of Type II odontoid fractures treated with a single anterior screw construct. Bhanot et al.23 found that anterior screw fixation resulted in fracture union with minimal complications in 16 of 17 patients. In another retrospective series involving 26 cases of acute Type II odontoid fractures treated with single-screw anterior fixation, nearly all patients exhibited a solid fusion.226 In a comprehensive review of the literature, Hsu and Anderson128 reported overall union rates of Type II fractures treated with odontoid screw fixation to be 82%.

 

Both single-and double-screw techniques can be used to stabilize Type II odontoid fractures. In theory, the addition of a second screw enhances stability and limits the potential for rotation, although no clinical advantage has definitively been shown. ElSaghir and Bohm84 reported a 100% healing rate in 30 patients who underwent two-screw fixation. Graziano et al.110 maintained that single- or double-screw fixation of a simulated odontoid fracture produced stability comparable with posterior C1–C2 wiring. In a radiographic and CT study of 92 normal odontoid processes, Nucci et al.181 concluded that two 3.5-mm screws could be safely contained in 95% of cases. McBride et al.164 advocated that a single 4.5-mm headless Herbert screw was stronger than two 3.5-mm AO lag screws for fixation of simulated Type II fractures.

 

Several limitations to odontoid screw fixation have been reported. As indicated previously, healing rates with anterior odontoid osteosynthesis rarely exceed 85%.128 Moreover, in a cadaveric study, Doherty et al.74 found that a single anterior odontoid screw provided only half the strength of the intact bone. Aebi et al.1 reported a higher (12%) nonunion and major complication (24%) rate than previously documented with anterior screw fixation. While effective for stabilization of the fracture, Verheggen and Jansen248 reported hypomobility in 11 (and frank C2–C3 autoarthrodesis in two) of 18 patients who underwent anterior screw fixation. In keeping with this finding, Hsu and Anderson128 proposed that the preservation of atlantoaxial rotation in odontoid screw fixation was only a theoretical advantage, with motion at the C1–C2 articulation found to be reduced by 50% in most instances.

 

Recent advancements in image-guidance have been purported to increase the accuracy of odontoid screw placement. However, Battaglia et al.19 found that computer-assisted fluoroscopic navigation produced comparable accuracy, with standard fluoroscopy in 22 cadaveric cervical specimens undergoing odontoid screw placement.

 
Posterior C1–C2 Fusion
 
Indications
 

Posterior C1–C2 stabilization and fusion can be performed in any case in which surgery is indicated for an odontoid fracture.160 There are a variety of methods by which a surgeon may stabilize and fuse this segment, each of which has unique advantages and risks. Sublaminar wiring techniques, such as the Brooks or Gallie methods, carry the lowest risk of complications but necessitate adjunctive halo-thoracic immobilization and can accentuate posteriorly displaced fractures. Transarticular screw fixation requires reasonable reduction of the fracture so that there is sufficient overlap of the C1–C2 lateral masses through which to pass the screws. C1 lateral mass C2 instrumentation is the most versatile fixation method, as it does not require anatomical reduction and, in fact, can be used to help reduce fractures. However, it has a higher risk of complications and is a technically demanding procedure.189

 
Results
 

While they do not provide clinical data, in vitro biomechanical studies have compared the strength of commonly used surgical constructs. In the presence of a simulated dens fracture, one study showed that anterior or posterior C1–C2 transarticular screws and C1–C2 lateral mass fixation provided comparable stability whereas C1 lateral mass C2 intralaminar screw fixation was less stable.148 The addition of posterior sublaminar wiring provides additional stability only for posterior C1–C2 transarticular screw constructs. Dmitriev et al.73 reported that C1 lateral mass and C2 pedicle screws were associated with the best biomechanical properties in these fractures, whereas C1 lateral mass and C2 intralaminar screws were superior to C1 lateral mass and C2 pars fixation.

 

Both Clark and White59 and Andersson et al13 reported healing rates in excess of 90% for Type II odontoid fractures treated with posterior fusion. The review of Hsu and Anderson128 showed an overall healing rate of 93% for posterior techniques. Likewise, the comprehensive analysis conducted by Patel and colleagues189 documented a 100% fusion rate and 10.5% complication rate in 19 patients with unstable Type II odontoid fractures treated using posterior C1–C2 instrumentation. Vieweg et al.251 maintained that patients treated with fusion constructs that incorporated C1 were at greater risk of developing chronic pain.

 
Anterior C1–C2 Fusion
 
Indications
 

Although not widely used, some surgeons propose that anterior stabilization and fusion of C1–C2 may be suitable in selected cases. Suggested indications include failure of posterior fusion, soft-tissue injury over a proposed posterior surgical incision site, or contraindication to prone positioning.

 
Results
 

Reindl et al.195 performed an anterior C1–C2 fusion for concomitant odontoid and C1 ring fractures in one patient and reported solid fusion at 4 months. Vaccaro et al.242 also documented reasonable success using this technique as a salvage operation for failed posterior C1–C2 fusion.

 
Special Circumstances
 
Geriatric Odontoid Fractures
 

The optimal treatment of odontoid fractures in elderly patients remains unclear because of the varied treatment methods and the inherent limitations of studies currently available in the literature. In a retrospective cohort of 29 patients older than 65 years, anterior screw fixation and nonoperative management exhibited a high failure rate and inferior outcomes.13 In contrast, the authors found that all patients treated by posterior atlantoaxial fusion achieved bony union.

 

A number of retrospective studies have published higher mortality rates and increased complication rates among elderly individuals treated with halo-fixation for odontoid fractures.217,230 Other studies, however, have not endorsed these findings,123,141,211 indicating that halo-thoracic immobilization may still be an acceptable treatment in certain patients older than 65 years. Nonetheless, Hsu and Anderson128 recommended against halo immobilization in the elderly. They suggested that an external orthosis or CTO be used for Type I and III fractures as well as for stable Type II injuries.128 These authors proposed C1–C2 posterior fusion for unstable Type II odontoid fractures.

 

In a systematic review of the published literature regarding surgical intervention for odontoid fracture in patients older than 65 years, White et al.258 reported a 10% mortality rate and a similar risk of nonunion. Major complications following surgery included pneumonia in 10%, respiratory failure in 8%, cardiac failure in 7%, and deep venous thrombosis in 3%. Mortality rates were similar between anterior and posterior approaches, although site-specific complications and the need for revision were higher in patients treated with anterior fixation. Chaudhary et al.52 compared treatment in a cervical collar with surgical intervention in a small series of patients older than 70 years with Type II odontoid fractures. Although complete union was seen only in approximately 70% of the cohort treated with external immobilization, no instances of instability were encountered. In addition, mortality was higher in the surgically treated group and, although comparable, objective pain scores were slightly higher among those managed operatively.

 

In one of the largest studies to assess mortality among elderly patients treated for Type II odontoid fractures, Schoenfeld et al.211 reported a 39% mortality rate at 3 years postinjury regardless of intervention. In the short term, mortality was lower among those treated surgically than those in the nonoperative group. However, a higher mortality was documented in patients aged 85 years and older who underwent surgical intervention. Operative management was found to enhance survival in patients aged 65 to 74 years. This group concluded that, similar to hip fractures, odontoid injuries were a significant event in the elderly that were associated with an increased risk of mortality within 1 year of injury.211

 
Odontoid Nonunion
 

The effective management of odontoid nonunions is notoriously difficult. Both anterior and posterior approaches have been advocated in the past, but recommendations are limited due to the poor quality of available reports, as well as limited sample sizes. Based on a series of only eight patients with odontoid nonunions, Blauth et al.26 developed a classification system intended to aid treatment. Type I nonunions are considered stable and are not substantially displaced, Type II nonunions are stable but grossly displaced, Type III nonunions are unstable, and Type IV nonunions are posttraumatic os odontoideum. The authors recommended posterior transarticular C1–C2 fixation for unstable fractures (Type III or IV) that could be safely reduced.26

Authors’ Preferred Method of Treatment for Cervical Spine Fractures and Dislocations

 
 
Treatment Algorithm
 

As there is wide variation in the treatment of odontoid fractures, the authors’ treatment algorithm relies on a variety of treatment techniques (Fig. 44-42). Notwithstanding those cases that represent occult craniocervical dissociation, Type I fractures are treated in a hard cervical collar for 8 weeks, after which flexion–extension views are obtained to confirm stability. It is, however, important to realize that isolated Type I fractures are exceedingly rare, with the senior author having encountered only one case in his practice. Most nondisplaced Type II fractures in young patients are treated in a halo-thoracic vest, whereas most nondisplaced Type III fractures are treated in an external orthosis. Displaced Type II and III fractures in young patients are first reduced using halo traction. Once acceptable alignment has been achieved, a halo vest is fitted in patients who are neurologically intact and in whom there are no relative contraindications, such as significant pulmonary trauma, to wearing a halo vest. Following reduction, it is the authors’ preference to perform a posterior C1–C2 stabilization and fusion in those with neurologic deficits. One of the most challenging situations is an irreducible odontoid fracture. In such cases, an open reduction is performed through a posterior approach utilizing C1 lateral mass and C2 isthmus screws. An elevator inserted into the fracture site can also be used to aid in reduction (see Fig. 44-28).

 
Rockwood-ch044-image042.png
View Original | Slide (.ppt)
Figure 44-42
Odontoid fracture treatment algorithm.
Rockwood-ch044-image042.png
View Original | Slide (.ppt)
X
 

For elderly individuals with displaced Type II odontoid fractures, surgery is considered for those aged 65 to 80 years as long as physiology, medical comorbidities, and concomitant injuries will allow. If a patient has multiple medical issues and is in low demand in terms of function, a decision may be made to defer surgery. Unless their injury is associated with neurologic deficit, those aged 80 years and older will usually be managed with external immobilization if at all possible.

 
Posterior C1–C2 Stabilization and Fusion with C1 Lateral Mass C2 Isthmus Screws
 
Preoperative Planning
 

Preoperative planning for C1 and C2 screw placement has been described elsewhere in this chapter. If the fracture cannot be reduced by closed means, the direction of displacement and fracture morphology is noted on CT scans to determine the intraoperative method of reduction. For example, posteriorly displaced fractures with bayonet apposition will require distraction and an anterior force delivered to the C1 lateral mass screws. The converse would apply to an anteriorly bayoneted fracture.

 
Positioning
 

Spinal cord monitoring is used for this procedure. After intubation, the patient is carefully logrolled into the prone position on a standard electric operating table fitted with transverse chest and thigh supports. Traction, preferably through a halo ring, is maintained via an apparatus attached to the head of the table. Once the patient is positioned appropriately, a lateral fluoroscopic image is obtained to confirm that reduction has been maintained. If not, a gentle closed reduction maneuver can be performed using weights or manual traction. Angulation can be corrected by extending or flexing the head. Once reduction on the lateral view is confirmed, an AP image is obtained to ensure adequate visualization of the C1–C2 joints and odontoid process.

 
Approach
 

A standard posterior midline approach to expose the posterior elements of C1 and C2 is performed, as described earlier.

 
Technique
 

The techniques for insertion of C1 and C2 screws, as well as C1 sublaminar cables, have been described previously. Once these are in place, the reduction of the fracture should be reconfirmed on a lateral image. If reduction was lost intraoperatively, a reduction maneuver can be performed using the instrumentation as anchors for manipulation. With the fracture held in an appropriate position, the connecting rods and locking nuts are then placed to maintain reduction.

 
Postoperative Care
 

A hard cervical collar is maintained for 3 months. This may not be as necessary with modern instrumentation techniques and can potentially be removed as early as 4 to 6 weeks depending on fracture stability. Radiographs are obtained immediately after surgery and at 2 weeks, 6 weeks, 3 months, 6 months, and 1 year following surgery.

 
Pearls and Pitfalls
 

While anatomic reduction is easily obtained and maintained in most instances, intraoperative reduction maneuvers may be required in difficult cases. This can be performed most readily using the C1–C2 screws. Distraction between the screws can help unlock interdigitated fracture fragments. Anterior forces can be delivered to C1 or C2 by using the screw inserter device. Posterior reduction forces are applied through the C1 sublaminar cable. If necessary, a number 3 or 4 Penfield elevator can be inserted into the fracture site to aid in reduction.

 

Under lateral fluoroscopic guidance, the elevator is advanced along the medial C2 pedicle wall. Carefully holding the elevator’s handle laterally to avoid impingement of the spinal cord, the tip of the instrument is angled into the fracture site (see Fig. 44-28). With posteriorly displaced fractures, the Penfield is angled superiorly whereas it is angled inferiorly for anteriorly displaced fractures. Once it has engaged the fracture site, it may be necessary to gently tap the instrument until the blade has reached the anterior aspect of the displaced fragment. Next, the elevator is levered superiorly or inferiorly as indicated by the direction of displacement. This maneuver will apply a direct corrective moment to the fracture fragments. While maintaining the Penfield elevator in place, anterior or posterior reduction forces are applied as necessary to finalize the reduction. With the rods already in place, the locking nuts are tightened to maintain the alignment. Importantly, a final lateral view should be obtained with the traction weight removed to confirm that the reduction is held appropriately by the instrumentation.

 
Complications
 

There are a variety of approach and instrumentation-related complications that can occur with this surgical technique. Although C1 lateral mass C2 isthmus screw constructs enhance stability at the atlantoaxial joint, instrumentation failure can still occur. Pseudarthrosis can also result from insufficient stabilization, patient-based factors such as an immunocompromise state or nicotine abuse, and poor bone graft technique. Neurologic decline may be precipitated during reduction maneuvers, overzealous dissection around the ventral aspect of the posterior C1 ring, or screw malposition.

 
Hangman’s Fractures (Traumatic Spondylolisthesis, C2–C3)
 
Mechanism of Injury
 

First described by Haughton in the 19th century,262 the term “hangman’s fracture” as a synonym for traumatic disruption of the C2 pars interarticularis is a misnomer. Postmortem examination of corpses following judicial hanging has shown that the characteristic hangman’s fracture was a rare occurrence, with most victims exhibiting no fracture at all. In a critique based on semantics, Niijima177 objected to the term because it is the “hanged man” and not the hangman, or executioner, who sustains the fracture.

 

The mechanism of injury in hangman’s fractures has been presumed to be a flexion force. However, recent biomechanical evidence suggests that the varying fracture patterns are the result of different forces imparted to the C2 pars with the neck in different postures.232

 
Diagnosis and Classification
 

The most widely used classification system for hangman’s fractures was proposed by Levine and Edwards.153 In this system, a Type I fracture is minimally displaced with no evidence of translation or angulation and no substantial injury to the C2–C3 disc space. Type II fractures are characterized by both angulation and translation and presumably occur because of extension. They are associated with substantial injury to the C2–C3 interspace. In contrast, Type IIa fractures occur as a result of flexion and are characterized by marked angulation with minimal translational deformity. Type III fractures include any C2 pars fracture associated with a dislocation of the C2–C3 facet joint (Fig. 44-43).

 
Figure 44-43
Classification of C2 hangman’s fractures (traumatic spondylolisthesis).
Rockwood-ch044-image043.png
View Original | Slide (.ppt)
X
 

Starr and Eismont223 added to this classification by describing the Type Ia fracture, which represents injuries in which a portion of the posterior C2 vertebral body is in continuity with one of the pars fracture fragments. Noting a high incidence of neurologic deficit in association with this subcategory of fracture, Starr and Eismont attributed this to canal compromise resulting from posterior displacement of the posterior arch–posterior vertebral body fragment complex as opposed to the usual, canal-expanding, fracture pattern. The most commonly encountered fracture morphology appears to be Type I, with Types II and III being rare.111,153

 
Nonoperative Treatment
 
Indications
 

Most hangman’s fractures can be managed nonoperatively. Nearly all Type I injuries (unless associated with neurologic compromise or other cervical injury) are effectively treated in a cervical collar. Type Ia fractures have a high healing rate and are also well treated in a cervical orthosis, unless associated with spinal cord injury. Type II fractures are inherently less stable and are best treated by traction followed by halo vest immobilization. Type IIa fractures should not be placed in traction, as this can accentuate the deformity. Reduction is achieved by extension and compression delivered through a halo apparatus. Neurologic deficit, although rarely associated with hangman’s fractures, is a contraindication to conservative management, as are Type III injuries because of the presence of facet dislocation.

 
Results
 

Coric et al.63 reported good results using external cervical orthoses to manage patients with hangman’s fractures with less than 6-mm displacement. In a recent systematic review of previously published literature, Li and colleagues154 concluded that most hangman’s fractures can be adequately treated using nonoperative means, with surgical stabilization reserved for cases in which dislocation or substantial instability is present.

 

In a retrospective series, Vaccaro et al.243 reported the results of traction, followed by early halo vest immobilization in 31 patients with Type II and IIa hangman’s fractures. Acceptable alignment was achieved and maintained in 21 of 27 Type II and all Type IIa fractures. In the other six cases of Type II injury, the fracture displaced in the halo vest necessitating the reapplication of traction. In attempting to analyze the injury characteristics of these failures, the group of Vaccaro et al.243 found that all had initial fracture angulations exceeding 12 degrees. Despite failure of the initial procedure, reapplication of traction was successful in every case.

 
Operative Treatment
 

The ideal surgical technique for hangman’s fractures has not been defined, as there are proponents of anterior fusion, posterior fusion, and osteosynthesis without fusion. Posterior fusion typically necessitates a construct incorporating C1, C2, and C3.57 Anterior instrumentation is performed only at C2–C3, thus preserving motion at the C1–C2 articulation as compared with the posterior procedure. In an in vitro biomechanical study, Duggal et al.76 found that posterior C2–C3 lateral mass fixation was stronger than anterior C2–C3 plating, while the latter was stronger than direct osteosynthesis of the C2 pars with a screw. In a more relevant biomechanical study, Chittiboina et al.57 reported that anterior C2–C3 instrumentation increased stiffness in flexion and extension over intact specimens. Posterior fusion from C1 to C3 was superior to the anterior technique. Unfortunately, the degree of rigid fixation necessary for clinical success has not been determined, and it would appear that satisfactory outcomes have been derived using all three methods. There are various advantages and limitations associated with each technique, and these may be tailored to the needs of particular patients and fracture patterns. For example, posterior fusion may have a decided advantage over anterior fixation in Type III fractures because of the associated facet injuries and potential need for open reduction.

 
Posterior Surgery
 
Indications
 

Posterior surgery can be performed for Type II, IIa, or III fractures. Reduction, stabilization, and fusion of the C2–C3 facet joint are required for Type III injuries. Akin to anterior odontoid screw fixation, Type II and IIa fractures that can be adequately realigned may be treated via direct osteosynthesis with a C2 pedicle screw, provided the patient has amenable anatomy.

 
Results
 

Bristol et al.42 reported on the use of lag screws inserted into the C2 pars in a patient who developed anterior displacement of his or her C2 pars fractures while in a halo vest. Taller et al.229 also reported the successful use of C2 pedicle screws inserted with guidance to treat 10 patients with hangman’s fractures.

 

In a small case series, Boullosa et al.39 used posterior fusion for 10 patients with hangman’s fractures in whom a halo vest was contraindicated or nonunion had developed. In one of the larger series focused on treatment of hangman’s fractures, Verheggen and Jansen249 documented good radiographic and clinical results in patients with Type II, IIa, and III fractures using posterior fusion-based techniques.

 
Anterior Discectomy and Fusion
 
Indications
 

Type II or IIa fractures are most amenable to anterior surgery if nonoperative treatment is contraindicated or unsuccessful. Type III fractures require reduction of the C2–C3 joint prior to stabilization and generally necessitate a posterior approach. As the C2 articular processes are not in continuity with the C2 body because of the fracture pattern, anterior reduction maneuvers are difficult in Type III fractures.

 
Results
 

Tuite et al.235 found anterior discectomy and fusion to be effective in five patients in whom nonoperative treatment failed. At follow-up ranging from 3 to 28 months, a 100% fusion rate was reported. In the largest series to examine outcomes following treatment of hangman’s fractures, Ying et al.262 reported satisfactory results in 30 patients with Type II, IIa, or III injuries. Mean follow-up was 1 year in this cohort, and a 100% fusion rate was documented by 6 months. Neurologic status improved in all patients who had presented with preoperative neurologic deficits, and no graft or plate-related complications were reported.

Authors’ Preferred Method of Treatment for Cervical Spine Fractures and Dislocations

 
 
Treatment Algorithm
 

It is the authors’ strong preference to treat patients with Type I and Ia fractures using a hard cervical collar, provided no neurologic compromise is evident (Fig. 44-44). Patients with Type II fractures are first reduced in halo-based traction. After reduction has been adequately achieved, a halo vest is also used for definitive immobilization. Radiographs should be repeated at regular intervals to ensure that acceptable reduction has been maintained (Fig. 44-45). If reduction fails, posterior fusion using a C1 lateral mass, C2 isthmus screw, and C3 lateral mass screw construct is performed.

 
Figure 44-44
Hangman’s fracture treatment algorithm.
 
ACDF, anterior cervical discectomy and fusion.
ACDF, anterior cervical discectomy and fusion.
View Original | Slide (.ppt)
Figure 44-44
Hangman’s fracture treatment algorithm.
ACDF, anterior cervical discectomy and fusion.
ACDF, anterior cervical discectomy and fusion.
View Original | Slide (.ppt)
X
 
Figure 44-45
 
Lateral radiograph (left) and sagittal CT scan (right) of a young man treated in a halo fixator for a Type II hangman’s fracture. Although there was some loss of reduction, he remained neurologically intact and without neck pain at final follow-up.
Lateral radiograph (left) and sagittal CT scan (right) of a young man treated in a halo fixator for a Type II hangman’s fracture. Although there was some loss of reduction, he remained neurologically intact and without neck pain at final follow-up.
View Original | Slide (.ppt)
Figure 44-45
Lateral radiograph (left) and sagittal CT scan (right) of a young man treated in a halo fixator for a Type II hangman’s fracture. Although there was some loss of reduction, he remained neurologically intact and without neck pain at final follow-up.
Lateral radiograph (left) and sagittal CT scan (right) of a young man treated in a halo fixator for a Type II hangman’s fracture. Although there was some loss of reduction, he remained neurologically intact and without neck pain at final follow-up.
View Original | Slide (.ppt)
X
 

As described by Levine and Edwards,153 patients with Type IIa fractures are immediately placed into a halo vest to allow reduction via compression and extension of the neck. Type III fractures are treated with early open reduction and instrumented fusion of C1, C2, and C3. Importantly, the C2–C3 disc space must be carefully assessed following facet reduction, as persistent deformity in this region can be present. If there is persistent deformity, staged anterior C2–C3 instrumented fusion may be required to offset biomechanical strain on the posterior construct and the consequent increased risk of failure.

 
Subaxial Cervical Fractures and Dislocations (C3–C7)
 
Classification
 
Overview of Classification Systems
 

Classification of a spinal injury should ideally be based on a system that is comprehensive, clinically prognostic, aids in decision making, and is user-friendly, valid, and reproducible.189 Most classifications for subaxial cervical trauma do not meet the above criteria and many have not been validated, or even determined to be reproducible, outside of the centers in which they were developed.189 While there is a lack of agreement regarding the most useful system, the mechanistic classification of Allen et al.5 is among the best known and its terminology has been influential.

 
Mechanistic Classification of Subaxial Cervical Injuries
 

Allen et al.5 reviewed 165 cases of subaxial cervical spine fractures and dislocations to develop a classification system on the basis of the mechanism of injury. Injuries were categorized into one of the following groups: compressive flexion (CF), vertical compression, distractive flexion (DF), compressive extension (CE), distractive extension (DE), and LF. Within each group, injuries were divided into grades of severity. In this retrospectively developed system, the likelihood and extent of neurologic injury was related to the group and severity of injury. Allen et al. hypothesized that (a) both major and minor forces produce injury, (b) the vectors (or direction) of these forces can be deduced from radiographs, (c) the amount of energy relates to the severity of injury, (d) injuries can be organized into groups on the basis of the force vectors, and (e) injuries can be further subdivided on the basis of the energy of trauma.5 However, the entire concept of the Allen and Ferguson system has not been validated independently since its inception.

 
Compressive Flexion
 

CF injuries are divided into five stages (Fig. 44-46). The initial injury is postulated to occur through flexion of the spine within the facet joints. The anterior column (vertebral body) becomes increasingly compressed and shortened. Subsequently, the posterior ligamentous structures fail this being indicated by interspinous gapping and local kyphosis. With increased energy, the facet joints will fail, leading to translational deformity. The distinguishing radiographic features of each stage should be understood and it must be appreciated that the stages follow one another. Thus, stage 3 lesions also demonstrate the features described for stages 1 and 2.

 
Rockwood-ch044-image046.png
View Original | Slide (.ppt)
Figure 44-46
The five stages of compression flexion injuries.
Rockwood-ch044-image046.png
View Original | Slide (.ppt)
X
  •  
    CF stage 1: Blunting of the anterosuperior vertebral body margin.
  •  
    CF stage 2: Beak appearance of the anterosuperior vertebral body margin; a sagittal vertebral body split may also be present.
  •  
    CF stage 3: Oblique primary fracture line that extends from the anterior vertebral body to the inferior endplate. (This has been subsequently described by other authors as a so-called teardrop fracture.96)
  •  
    CF stage 4: In addition to stage 3 features, posterior translation of the upper vertebra measuring less than 3 mm.
  •  
    CF stage 5: Posterior translation of the upper vertebra measuring 3 mm or more, facet gapping indicating anterior and posterior ligamentous injury.
 
Vertical Compression
 

Vertical compressive (VC) lesions are thought to arise primarily from axial loads to the cervical spine.5 However, the final stage of the injury may result from flexion or extension forces, which ultimately produce either posterior or anterior ligamentous injury depending on the direction of the force (Fig. 44-47).

 
Rockwood-ch044-image047.png
View Original | Slide (.ppt)
Figure 44-47
The three stages of vertical compressive injuries.
Rockwood-ch044-image047.png
View Original | Slide (.ppt)
X
  •  
    VC stage 1: Central superior or inferior endplate fracture.
  •  
    VC stage 2: Superior and inferior endplate fractures, sometimes with vertebral body fracture lines that give the appearance of a quadrangular fracture fragment.
  •  
    VC stage 3: Vertebral body comminution, with or without retropulsion of fragments (this has been referred to as a burst-type cervical fracture by some surgeons), with or without kyphotic (late flexion type), or translational (late extension type) deformity.
 
Distractive Flexion
 

DF injuries are thought to occur primarily from flexion forces that rotate about an axis anterior to the vertebral body. Thus, distraction and failure of the posterior ligaments can occur without significant vertebral body fracture. In this injury group, an increasingly higher stage of injury does not always correlate with an increased degree of instability (Fig. 44-48).

 
Rockwood-ch044-image048.png
View Original | Slide (.ppt)
Figure 44-48
The four stages of distractive flexion injuries.
Rockwood-ch044-image048.png
View Original | Slide (.ppt)
X
  •  
    DF stage 1: Facet subluxation, gapping of the spinous processes, indicating failure of the PLC, with or without blunting of the anterosuperior vertebral body (similar to CF stage 1).
  •  
    DF stage 2: Unilateral facet dislocation, usually PLC is intact, rotational deformity.
  •  
    DF stage 3: Bilateral facet dislocations, 50% translation of the upper vertebral body over the lower vertebral body.
  •  
    DF stage 4: 100% translation of the upper vertebral body over the lower vertebral body. (Appearance of a so-called floating vertebra.)
 
Compressive Extension
 

CE injuries are divided into five stages (Fig. 44-49). They are postulated to start with compression of the posterior elements without failure of the anterior ligaments. Further injury results in failure of the anterior ligamentous structures, followed by the posterior complex.

 
Rockwood-ch044-image049.png
View Original | Slide (.ppt)
Figure 44-49
The five stages of compressive extension injuries.
Rockwood-ch044-image049.png
View Original | Slide (.ppt)
X
  •  
    CE stage 1: Posterior arch fracture that may be a facet, pedicle, or lamina fracture, with or without rotation that can result in mild anterior translation. (These are more commonly referred to as lateral mass fractures.)
  •  
    CE stage 2: Bilateral lamina fractures can occur at multiple levels.
  •  
    CE stage 3: Bilateral lamina, facet, and pedicle fractures without vertebral body displacement. This injury is more often described as a floating lateral mass fracture.
  •  
    CE stage 4: As for CF stage 3, with partial anterior vertebral body displacement.
  •  
    CE stage 5: As for CF stage 3, with 100% anterior vertebral body displacement.
 
Distractive Extension
 

DE injuries, like DF injuries, are associated with substantial ligamentous injury. Initial failure occurs through the anterior ligaments (Fig. 44-50).

 
Rockwood-ch044-image050.png
View Original | Slide (.ppt)
Figure 44-50
The two stages of distractive extension injuries.
Rockwood-ch044-image050.png
View Original | Slide (.ppt)
X
  •  
    DE stage 1: Abnormal widening of the disc space may be associated with avulsion fractures of the anterior vertebral body margin. No evidence of posterior translation.
  •  
    DE stage 2: DF stage 1 with posterior translation.
 
Lateral Flexion
 

LF injuries occur through compression on one side of the spine. With further energy, the contralateral side can fail under tension.

  •  
    LF stage 1: Unilateral uncovertebral fracture or asymmetric vertebral body compression.
  •  
    LF stage 2: Vertebral body, or posterior arch fractures, with lateral translation or unilateral facet gapping, coronal angular deformity is noted on an AP radiograph or coronal CT scan.
 

The classification system of Allen et al.5 is the most frequently used classification for subaxial cervical spine injuries. Despite this, it has not been independently validated since its publication in 1982. Intra- and interobserver reliability has not been evaluated, to the authors’ knowledge, and the influence of the injury groups on subsequent decision making has not been defined.

 

Subsequent studies have demonstrated that a wide spectrum of injury patterns can result from a single mechanism. Torg et al.233 found facet dislocations, teardrop vertebral body fractures, and anterior translational injuries at the C3–C4 segment in football players injured through axial loading of the head and cervical spine. According to Allen et al.,5 these would have had to occur from DF, CF, and either CE or VC mechanisms, respectively. The disparity between these findings underscores the very complex three-dimensional biomechanical interactions between the cervical spine and even simple, unidirectional, forces. Postulating the direction or mechanism of injury, although a common academic exercise, may not lead to accurate or useful clinical information. Perhaps what is more important is the determination of the integrity of the ligamentous complexes, as well as the overall stability of the cervical spine.78,189,241

 
Subaxial Cervical Injury Scoring Systems
 

Two scoring systems for subaxial cervical spine injury were devised within the last decade to try to characterize cervical spine trauma more consistently and potentially guide treatment decisions.12,78,189,241 These include the Cervical Injury Severity Score, described by Anderson et al.,12 and the Subaxial Cervical Injury Classification (SLIC) developed by Vaccaro, Dvorak, and the members of the Spine Trauma Study Group.78,189,241 In a more recent review of the literature, Patel and coworkers189 maintained that the SLIC and Cervical Injury Severity Score were the only two available systems that could reliably determine treatment.

 
Cervical Injury Severity Score
 

Anderson et al.12 proposed a numerical scoring system that assigns a value to the injury severity of each of four columns of the subaxial cervical spine: anterior, posterior, right lateral, and left lateral. In reviewing 34 different cases, 15 examiners showed high intra- and interobserver agreement. The authors proposed that the system may also be able to predict the need for surgery and the presence of neurologic deficit. Specifically, 11 of 14 patients with a score of at least 7 had a neurologic deficit, whereas only 3 of 20 with a score less than 7 exhibited neural injury. To date, prospective evaluation of the clinical validity of this system has not been reported. Moreover, Patel et al.189 maintained that its complexity limits its widespread use.

 
Subaxial Cervical Injury Classification
 

The SLIC system both classifies and scores the severity of subaxial cervical spine injuries.78,241 The system assigns values within three injury categories (injury morphology, discoligamentous stability, and neurologic injury). Injury types include compression or burst fractures, distraction injury, and rotational or translational injury. The status of the discoligamentous complex is defined as intact, indeterminate, or disrupted. Neurologic status can be scored as intact, root injury, complete cord injury, and incomplete cord injury, and there is also a modifier for ongoing cord compression with neurologic deficit that adds an additional point. A normal spine has a score of 0. The most severe injury (e.g., translational injury with disruption of the PLC and incomplete cord injury with sustained cord compression) yields a score of 10. Injuries that result in scores of 3 or less are usually treated nonoperatively, whereas those with scores exceeding 5 are generally treated surgically.78,189,241 The treatment of injuries with a score of 4 is usually determined by other factors such as concomitant injuries, medical comorbidities, and/or the presence of neurologic deficit.

 

Inter- and intraobserver reproducibility have been reported to be high, and the SLIC system represents one of the few classifications capable of determining treatment.189 In addition, Dvorak et al.78 proposed that the system was useful in predicting the type of surgery to be performed. In this analysis, the authors found that surgeons agreed with the treatment recommendation proposed by the system’s algorithm in 93% of cases. However, the clinical validity of the system has yet to be tested in a prospective fashion.

 

Bono et al.34 have proposed a Subaxial Cervical Injury Description System that can be used in conjunction with the SLIC. The Subaxial Cervical Injury Description System was intended to standardize the nomenclature used in describing cervical spine trauma and is limited to 11 injury types: spinous process fracture, isolated lamina fracture, unilateral facet dislocation, bilateral facet dislocation, facet subluxation, flexion teardrop fracture, lateral mass fracture, compression fracture, burst fracture, anterior distraction injury, and transverse process fracture. This system has demonstrated only moderate interrater agreement but substantial intrarater reliability.34 Nonetheless, only burst fractures, lateral mass fractures, flexion teardrop fractures, and anterior distraction injuries were found to have an interrater reliability of more than 50%.

 
Descriptive Classification of Subaxial Cervical Injuries
 

Cervical fractures and dislocations can be described without involving the mechanism of injury. This description is based on identifiable injury characteristics that are thought to influence mechanical stability and the method of treatment. Despite disagreement on a unified description system, several injury patterns are consistently reported in the literature, including those outlined in the Subaxial Cervical Injury Description System.34 It must be kept in mind, however, that these injuries often represent different stages along a continuum and many share similar characteristics.

 
Vertebral Body Fractures
 

Regardless of the mechanism of injury, vertebral body fractures are readily detected by plain radiographs and CT scans. Fractures may be simple wedge types, also known as compression fractures, in which there is anterior height loss and no posterior vertebral involvement. Teardrop fractures, described by Allen et al.5 as CF stage 3 injuries, demonstrate a characteristic primary fracture that extends obliquely from the anterosuperior vertebral body to the inferior endplate. These injuries can involve the endplate to a varying degree, and this can influence the decision to perform a discectomy or corpectomy if surgical treatment is planned. Burst fractures, much like their thoracic and lumbar counterparts, demonstrate extensive vertebral body comminution, varying degrees of height loss, and, most importantly, posterior vertebral body involvement with fragment retropulsion. One term that engenders confusion is the teardrop burst fracture. Teardrop fractures often have a midsagittal split in addition to posterior translation, which is often described as characteristic of a burst pattern. Quadrangular burst fractures, similar to the VC stage 2 injury described by Allen et al.,5 are sometimes distinguished in the literature from other vertebral body fractures. The clinical significance of this distinction is unknown and treatment tends to be similar. With any vertebral body fracture, the PLC can be disrupted because of translational, flexion, or rotational forces, and this factor plays a major role in determining the approach, and manner, of surgical fixation.78

 
Facet Injuries
 

Facet injuries are extremely common. While Allen et al.5 have suggested that they occur primarily through DF mechanisms, it is clear that rotational forces, axial compressive forces, and various other forces may also be responsible. Facet fractures can be associated with dislocations or other posterior arch injuries. Reports of facet fractures in the literature generally refer to isolated, unilateral, minimally displaced fractures of varying size. Facet fractures are often thought to be benign, but they may be associated with ligamentous disruption, leading to subluxation and instability. Because of this possibility, significant controversy exists regarding their initial treatment. Facet subluxations result from facet capsule and posterior ligament disruption. By definition, some portion of the articular surfaces at the involved level is still in opposition. Facet dislocations can be unilateral or bilateral. These are further described by a number of qualifiers, including perched or locked. In a dislocation, the articular surfaces are no longer opposed.

 

Cadaveric sectioning studies, as well as intraoperative observations, have indicated that unilateral dislocations may occur without complete PLC disruption and in many cases may be mechanically stable injuries. There may be some use in distinguishing facet dislocations from facet fracture–dislocations, in which the facet joint is dislocated, unilaterally or bilaterally, and fractured. With large facet fracture fragments, reduction can be difficult to achieve or maintain through closed techniques. In addition, extensive articular process fractures can preclude lateral mass instrumentation.

 
Pedicle and Lamina Fractures
 

Isolated, unilateral pedicle fractures usually suggest rotational instability. Pedicle and facet fractures are often referred to in the literature as lateral mass fractures. A coexisting lamina fracture and a pedicle fracture effectively negate the contribution of the adjacent facet joint to overall cervical stability. This has been categorized as a floating lateral mass fracture. Such fractures are potentially unstable and may require instrumented fusion.

 
Anterior Tension Band Disruption
 

The ALL and the intervertebral disc can fail in tension (Fig. 44-51). Without speculating about the mechanism behind this injury, widening of the intervertebral disc space is highly suggestive of anterior ligamentous disruption and suggests the possibility of spinal instability. Small avulsion injuries of the vertebral body can also result in teardrop-shaped fragments and are frequently referred to as extension-type teardrop fractures. The mechanism of injury is most likely extension, resulting in an avulsion fracture attached to the anterior ligamentous structures. This fracture is typically more common in elderly individuals and represents a stable injury pattern, especially if no kyphotic deformity is present at the level of injury.

 
Figure 44-51
 
Disruption of the anterior tension bend is evidenced by widening of the disc space at the injured level, as demonstrated in this lateral radiograph. This should be considered an unstable injury.
Disruption of the anterior tension bend is evidenced by widening of the disc space at the injured level, as demonstrated in this lateral radiograph. This should be considered an unstable injury.
View Original | Slide (.ppt)
Figure 44-51
Disruption of the anterior tension bend is evidenced by widening of the disc space at the injured level, as demonstrated in this lateral radiograph. This should be considered an unstable injury.
Disruption of the anterior tension bend is evidenced by widening of the disc space at the injured level, as demonstrated in this lateral radiograph. This should be considered an unstable injury.
View Original | Slide (.ppt)
X
 
Mechanism of Injury
 
Normal Mechanics
 

The biomechanics of cervical spine trauma can be considered in terms of force/load transmission and injury kinematics, or motion. While injuries arise from the interaction and relative proportions of both components, an understanding of the simplest forms of each component is useful when analyzing the processes responsible for cervical trauma.

 

One can consider an isolated axial compressive load applied to a single cervical vertebra as a fundamentally pure example of load transmission. Force, or load, is resisted primarily by the vertebral body. Its trabecular makeup is well designed for dissipating forces. A smaller portion of the force is borne by the facet joints. Force can be applied in different directions (e.g., shear, torsion, tension), with subsequent changes in the location and structures that experience maximal loads.

 

From a theoretical perspective, kinematics refers to cervical vertebral motion without consideration of the forces applied. The cervical spine is a series of three-joint complexes that permit motion through the intervertebral discs and facet joints. Kinematically, the remaining soft-tissue structures, such as the ALL and the PLC, place limits on and influence the patterns of vertebral motion. Like other joints, motion between two vertebrae occurs about instantaneous axes of rotation (IAR). Hinge-type joints, like the elbow, have a relatively fixed IAR that permits motion in only one plane. In contrast, motion between two cervical vertebrae and their associated ligamentous structures (referred to as a functional spinal unit) is multiplanar and occurs about many IARs. For example, sagittal motion occurs about an IAR within the subjacent vertebral body that changes with flexion and extension.257 Motion coupling is a kinematic phenomenon that describes an obligatory amount of axial rotation with LF of the cervical spine. This further limits the ability to define an exact IAR for the cervical spine.

 

The amount of normal cervical motion at each level has been extensively described.257 Knowledge of these figures can be important in assessing spinal stability after treatment. Flexion–extension motion is greatest at the C4–C5 and C5–C6 segments, averaging about 20 degrees. Axial rotation ranges from 2 to 7 degrees at each of the subaxial motion segments, whereas the majority (∼50%) of rotation occurs at the C1–C2 articulation. LF is 10 to 11 degrees per level in the upper segments (C2–C5). Lateral motion decreases in the subaxial region, with only 2 degrees observed at the cervicothoracic junction.

 
Structural Injury and Cervical Pathomechanics
 

Traumatic injury to the osseous and ligamentous structures alters both load transmission and the kinematics of the cervical spine. Under CF loads, simulated unilateral and bilateral facet injuries result in anterior displacement of the sagittal IAR and increased load transmission to the vertebral bodies.66 Anterior translation increases by 33% in the sectioned intervertebral disc, ALL, and PLL once flexion moments are applied.185 The addition of facet resection increases translation to 140%, which anatomically corresponds to complete occlusion of the spinal canal.185

 
Failure of Spinal Structures
 

Spinal trauma can lead to disruption of bone, ligaments, or both. Bone can fail under compression, tension, or shear loads. In contrast, ligaments fail only in tension, this being functionally likened to a rope that snaps. Perhaps the only exception to this rule is so-called shear failure of the intervertebral disc–endplate interaction, although this more accurately reflects tensile failure of the annular collagen fibers at the discovertebral interface.

 

Flexion of the cervical spine imparts compressive loads upon the vertebral body and disc and tensile loads upon the PLC, which comprises the supraspinous and interspinous ligaments and facet capsules. Trauma causing hyperflexion can lead to compressive failure of the vertebral body and/or tensile failure of the PLC. Varying combinations of anterior and posterior failure have been demonstrated experimentally as well as clinically.65

 

Extension of the cervical spine results in tensioning of the ALL and compression across the facet joints. Hyperextension trauma can lead to tensile failure of the ALL. However, this may not occur before posterior element compressive injuries occur. Additional distraction, shear, or rotation appears to be necessary before the ALL and the intervertebral disc will fail.

 

Cervical teardrop fragments may be created by shear failure of the anteroinferior vertebral body. Although thought to occur most commonly from a compressive–flexion moment, as hypothesized by Allen et al.,5 the superior and anterior displacement of the fragment supports the proposed shear injury mechanism (Fig. 44-52). Teardrop fractures are also often associated with wedging, or blunting, of the vertebral body, and sometimes there is an associated sagittal split. These additional fracture features indicate that the exact manner in which the spinal structures fail is a complex sequence of events that cannot be reliably deduced from examination of static imaging studies. Secondary injury mechanisms, resulting from recoil of the head in response to the primary force, can result in further ligamentous or osseous disruption. To confuse matters further, similar fracture patterns have been clinically observed as a result of axial loading, flexion, and extension injuries.5,68

 
Figure 44-52
The proposed mechanism of failure of the teardrop fragment is shear.
 
With forced flexion (red arrows), parallel, but opposite, forces (black arrows) are placed on the anteroinferior aspect of the vertebral body.
With forced flexion (red arrows), parallel, but opposite, forces (black arrows) are placed on the anteroinferior aspect of the vertebral body.
View Original | Slide (.ppt)
Figure 44-52
The proposed mechanism of failure of the teardrop fragment is shear.
With forced flexion (red arrows), parallel, but opposite, forces (black arrows) are placed on the anteroinferior aspect of the vertebral body.
With forced flexion (red arrows), parallel, but opposite, forces (black arrows) are placed on the anteroinferior aspect of the vertebral body.
View Original | Slide (.ppt)
X
 
Treatment of Specific Injuries
 
Compression Fractures
 
Diagnosis
 

Radiographs of simple compression fractures of the cervical spine show wedging of the anterior vertebral body without posterior vertebral body involvement. They can be considered stable if the facet joints are not subluxed or widened, there is no vertebral body translation, and there is minimal gapping of the interspinous processes (Fig. 44-53). There is often some degree of kyphosis, which should be carefully measured on a lateral radiograph using the Cobb method.36 Normally, there is between 2 and 4 degrees of lordosis between adjacent vertebrae. A kyphosis exceeding 11 degrees is strongly suggestive of PLC disruption. It is important that the kyphosis at the injured segment should be considered in relation to the measured “normal” lordosis of the adjacent uninjured segments. If the PLC is disrupted, the injury should be considered unstable and operative treatment is recommended.

 
Figure 44-53
Lateral cervical radiograph of a stable compression fracture.
 
There is minimal appreciable kyphosis, no translation, no facet joint gapping, and no evidence of interspinous process widening.
There is minimal appreciable kyphosis, no translation, no facet joint gapping, and no evidence of interspinous process widening.
View Original | Slide (.ppt)
Figure 44-53
Lateral cervical radiograph of a stable compression fracture.
There is minimal appreciable kyphosis, no translation, no facet joint gapping, and no evidence of interspinous process widening.
There is minimal appreciable kyphosis, no translation, no facet joint gapping, and no evidence of interspinous process widening.
View Original | Slide (.ppt)
X
 

Prior to the advent of MRI, implications about the integrity of the PLC were based primarily on proxy measures such as the amount of kyphosis or the degree of subluxation. In cases in which the integrity of the PLC is indeterminate on radiographs or CT scans, MRI can be used. While MRI has been criticized for being oversensitive, it can demonstrate discontinuity of the ligamentum flavum, interspinous and supraspinous ligaments, and reveal soft-tissue edema between the spinous processes. As patients with simple compression fractures are usually neurologically intact, determination of injury stability can have important implications for operative intervention.

 
Nonoperative Treatment
 
Indications
 

Patients with cervical compression fractures without posterior ligamentous injury can be treated nonoperatively. In the SLIC treatment algorithm, in the absence of PLC disruption or neural injury, compression fractures are treated with external orthoses.78 For C3–C6 injuries, a rigid cervical collar usually suffices. For injuries of C7 or T1, a cervicothoracic brace may provide better immobilization. If the injury is stable, the orthosis minimizes motion at the fracture site, which can decrease pain and facilitate resolution of muscular spasm. Attempts to correct minor kyphotic deformities are usually fruitless and ultimately unnecessary. A lateral radiograph should be obtained with the patient sitting upright or standing, as this may highlight occult instability. Compression fractures are usually healed by 3 months, at which time flexion–extension views should be obtained to rule out occult instability, either at the level of the injury or at a distant site, such as C1–C2, where an injury may have gone undetected at the time of initial presentation.

 
Results
 

As yet, there are no series reporting the results of nonoperative management for simple compression fractures of the subaxial cervical spine.

 
Operative Treatment
 
Indications
 

Surgical stabilization via an anterior or posterior approach should be considered for patients with evidence of posterior ligamentous injury. Posterior ligamentous injury is suggested by a segmental kyphosis greater than 11 degrees or a substantial amount of vertebral body wedging. Threshold values for the degree of height loss or PLC injury beyond which surgery is indicated have not been defined. MRI can be used as a means to determine the integrity of posterior soft-tissue structures in a compression fracture.

 
Results
 

It should be appreciated that a compression fracture with posterior ligamentous injury is essentially a stage 3 CF injury as described by Allen et al.5 without the characteristic teardrop-shaped fragment. The results of surgical treatment are discussed elsewhere in this chapter. Reasonably good results have been achieved with both anterior and posterior surgical techniques.

Authors’ Preferred Method of Treatment for Cervical Spine Fractures and Dislocations

 
 
Treatment Algorithm
 

Surgery is considered only for patients who have a compression fracture in association with a neural deficit or gross posterior ligamentous disruption. Prior to surgery, cervical traction, incorporating slight extension, can be used to realign the fracture. This is best performed in an awake cooperative patient. Although described in more detail for patients with facet dislocations, a herniated disc may also need to be ruled out using MRI prior to attempts at realignment. If the spinal canal is clear, a one- or two-level posterior fusion with instrumentation can be performed. Longer constructs are necessary if the fracture occurs at the cervicothoracic junction.6 As by definition compression fractures do not have associated retropulsed bone fragments, an anterior corpectomy for canal decompression is usually not required. If there is a herniated disc fragment or an underlying degenerative stenosis associated with a neurologic deficit, an anterior corpectomy is performed, followed by cage reconstruction and stabilization with a fixed angle plate.

 
Burst Fractures
 
Diagnosis
 

Cervical burst fractures are usually high-energy injuries. The characteristic radiologic sign is vertebral body comminution that involves the posterior vertebral body and is usually with retropulsed fragments that result in spinal canal compromise (Fig. 44-54). Spinal cord injury is common. Immediate realignment with cranial traction can help clear the canal to some degree, provided the PLL is intact.117 A magnetic resonance image and a CT scan can be useful in detecting spinal cord edema and the location of retropulsed vertebral fragments.

 
Figure 44-54
 
Lateral cervical radiograph (A) of a C4 burst fracture. There is relative kyphosis at the injured segment, in addition to disruption of the posterior vertebral body line. Computed tomographic scan (B) confirms the presence of posterior vertebral body fragment retropulsion into the spinal canal.
Lateral cervical radiograph (A) of a C4 burst fracture. There is relative kyphosis at the injured segment, in addition to disruption of the posterior vertebral body line. Computed tomographic scan (B) confirms the presence of posterior vertebral body fragment retropulsion into the spinal canal.
View Original | Slide (.ppt)
Figure 44-54
Lateral cervical radiograph (A) of a C4 burst fracture. There is relative kyphosis at the injured segment, in addition to disruption of the posterior vertebral body line. Computed tomographic scan (B) confirms the presence of posterior vertebral body fragment retropulsion into the spinal canal.
Lateral cervical radiograph (A) of a C4 burst fracture. There is relative kyphosis at the injured segment, in addition to disruption of the posterior vertebral body line. Computed tomographic scan (B) confirms the presence of posterior vertebral body fragment retropulsion into the spinal canal.
View Original | Slide (.ppt)
X
 
Nonoperative Treatment
 
Indications
 

Nonoperative treatment might be considered in neurologically intact patients with little vertebral body comminution and only the mildest degree of canal compromise. Any kyphotic deformity should measure less than 5 degrees, and there should be no indication of posterior ligamentous injury. Isolated burst fractures receive an SLIC score of 2 and, as such, do not warrant surgery.78 However, the presentation of an isolated cervical burst fracture without ligamentous disruption or neural compromise is rare.

 

It is the authors’ preference to use a halo vest or rigid CTO for nonoperative treatment because of the potential for vertebral body collapse. Radiographs should be obtained with the patient standing or sitting prior to discharge and rigorous comparisons made with supine films. Any subsidence, focal collapse or kyphosis is a strong indication for surgery. Patients should be followed weekly for the first month and immobilization maintained for at least 12 weeks.

 
Results
 

There are few contemporary reports of nonoperative treatment of cervical burst fractures. The work of Bucholz and Cheung45 is a classic study that documents satisfactory results for burst fractures treated with halo-thoracic immobilization.

 
Anterior Corpectomy and Stabilization
 
Indications
 

Patients with neurologic deficit, regardless of the integrity of the PLC, should be surgically stabilized.78 Posteriorly displaced vertebral body fragments are most readily removed through a direct anterior approach. A corpectomy of the injured vertebral body should be performed and the spinal canal fully decompressed. Intraoperative traction can help realign the spine if significant deformity exists (Table 44-4). The anterior column should be reconstructed with a bone graft or strut. It is the authors’ preference to insert a rigid titanium mesh cage filled with salvaged bone in addition to cancellous iliac crest autograft. Bone should be tightly packed into the cage, which may also enhance the surface area contact with the endplates. An anterior cervical plate is then applied to restore anterior stability. If the PLC appears to be disrupted, it is the authors’ preference to perform a posterior instrumented fusion, either during the same operation or in a staged fashion.

 
 
Table 44-4
Pearls and Pitfalls: Burst Fractures
View Large
Table 44-4
Pearls and Pitfalls: Burst Fractures
Pearls Pitfalls
Preoperative traction for realignment and partial decompression (ligamentotaxis) Avoid axial compression with stand-alone posterior constructs (e.g., lateral mass screws)
Combined anterior/posterior surgery usually required Ensure that PLC is intact if nonoperative care is elected
Corpectomized bone can be salvaged for fusion with titanium mesh cage Stand-alone anterior or posterior constructs may be prone to failure
 

PLC, posterior ligamentous complex.

X
 
Results
 

There are few reports of anterior corpectomy and plate stabilization for traumatic injuries, let alone cervical burst fractures. In a small series, Cabanela and Ebersold47 documented good results in eight patients followed for an average of 3 years treated with an anterior approach for burst fracture variants. In a series of mixed injuries, 20 of which were vertical compression fractures with tetraplegia, Barros Filho et al.18 found that, similar to the degenerative cervical spine, the addition of anterior instrumentation diminished the potential for graft dislodgement and enhanced patient mobilization.

 
Posterior Instrumentation and Fusion
 
Indications
 

As decompression is not undertaken, posterior instrumentation and fusion should be reserved only for patients who are neurologically intact and demonstrate evidence of posterior ligamentous disruption. If posterior fixation is planned as the only treatment, the vertebral burst fracture should demonstrate biomechanical integrity, with no comminution, kyphosis, or posterior retropulsion of fragments. Otherwise, the posterior construct will have a high risk of failure.

 
Results
 

Because of the rarity of isolated posterior fixation, no good data are available regarding the results of this technique for the treatment of cervical burst fractures.

Authors’ Preferred Method of Treatment for Cervical Spine Fractures and Dislocations

 
 
Treatment Algorithm
 

In the authors’ practice, burst fractures associated with normal alignment, no or minimal retropulsion, no associated neurologic deficit, and no posterior ligamentous injury may be treated nonoperatively. A rigid cervical collar is used for fractures of C3–C6, whereas a CTO is preferred for C7 fractures.

 

In the authors’ experience, however, the large majority of cervical burst fractures require surgery. After the spine is realigned with cervical traction, it is the authors’ preference to perform an anterior corpectomy of the fractured vertebra. This approach is used for patients with and without neurologic deficit. Anterior corpectomy enables effective decompression of the spinal canal from retropulsed bone fragments. With adequate endplate preparation, a titanium mesh cage filled with salvaged autograft is inserted for anterior column reconstruction. Traction is then released and an anterior cervical plate with fixed angle screws is applied.

 

Cervical burst fractures may be associated with dural tears that result in chronic CSF leaks or fistulae. In anticipation of finding a dural tear, the surgeon may decide to prepare the lateral thigh for a possible fascia lata graft. Alternatively, manufactured collagen-based dural patches can be used. Lumbar drains are usually not necessary, as the cervical thecal sac is effectively decompressed by using the reverse Trendelenburg position after surgery. Various other complications related to the surgical approach, graft, or instrumentation can also occur, and these are addressed elsewhere in this chapter.

 
Flexion-Type Teardrop Fractures
 
Diagnosis
 

Teardrop fractures are recognized by their characteristic fracture pattern, which has already been described. They often have a sagittal split within the posterior vertebral cortex, leading many authors to refer to them as burst fractures. Flexion-type teardrop fractures typically occur in younger patients as a result of high-energy trauma. Posterior ligament disruption is suggested by a kyphosis of more than 11 degrees or posterior vertebral body translation (Fig. 44-55). An MRI can confirm ligamentous injury. Patients often present with a neurologic deficit, and there is a high incidence of complete spinal cord injury in association with teardrop fractures.78

 
Figure 44-55
Sagittal computed tomographic scan of a C4 teardrop fracture.
 
This would be considered a stage 4 compressive flexion injury according to the Allen et al.5 system. The classic teardrop fragment can be seen, in addition to posterior translation (retrolisthesis) of the C4 vertebral body on the C5 vertebral body. A minimally displaced spinous process fracture is also noted at that level.
This would be considered a stage 4 compressive flexion injury according to the Allen et al.5 system. The classic teardrop fragment can be seen, in addition to posterior translation (retrolisthesis) of the C4 vertebral body on the C5 vertebral body. A minimally displaced spinous process fracture is also noted at that level.
View Original | Slide (.ppt)
Figure 44-55
Sagittal computed tomographic scan of a C4 teardrop fracture.
This would be considered a stage 4 compressive flexion injury according to the Allen et al.5 system. The classic teardrop fragment can be seen, in addition to posterior translation (retrolisthesis) of the C4 vertebral body on the C5 vertebral body. A minimally displaced spinous process fracture is also noted at that level.
This would be considered a stage 4 compressive flexion injury according to the Allen et al.5 system. The classic teardrop fragment can be seen, in addition to posterior translation (retrolisthesis) of the C4 vertebral body on the C5 vertebral body. A minimally displaced spinous process fracture is also noted at that level.
View Original | Slide (.ppt)
X
 
Nonoperative Treatment
 
Indications
 

There is a definite role for nonoperative treatment of cervical teardrop fractures. Minimally displaced fractures with little kyphosis and no PLC injury are stable. They can be treated in a rigid cervical collar or CTO, depending on the level of injury. Halo treatment can also be used to treat these injuries. The apparatus may also be employed as a means of realigning fractures, which can result in canal clearance in patients with spinal cord injury. Importantly, halo treatment of unstable teardrop fractures results in inferior radiographic results as compared with anterior surgery, although neurologic and clinical outcome scores were comparable in one study.95 The halo should be maintained in place for 3 months, provided acceptable alignment has been maintained. After the halo has been removed, flexion–extension radiographs are necessary to confirm that stability has been achieved.

 
Results
 

In a nonrandomized comparison of halo vest immobilization and anterior surgery, Fisher et al.95 found equivalent neurologic and clinical outcomes. Radiographic outcomes were superior with surgery, as, on average, a greater degree of kyphotic angulation was seen following nonoperative treatment. In an earlier study, Johnson and Cannon134 reported a low rate of late instability after nonoperative management of flexion teardrop fractures.

 
Operative Treatment
 
Anterior Surgery
 
Indications
 

In patients with a neurologic deficit, anterior corpectomy is usually performed to remove the posteriorly displaced vertebral body (Table 44-5). This is followed by anterior strut grafting and rigid plate fixation (Fig. 44-56). In some cases, an unstable teardrop fracture can occur in a neurologically intact patient. In these cases, anterior surgery entails a nondecompressive corpectomy, with resection of the majority of the vertebral body back to, but not through, the posterior wall. This is best reserved for injuries without retrolisthesis. Some surgeons prefer to perform a single-level discectomy or partial corpectomy. However, extensive endplate fracture appears to be a risk factor for anterior construct failure.135 If the initial injury demonstrated a significant degree of translational deformity, exceeding 3 to 3.5 mm, and the facet joints appear to be widened, posterior surgery is recommended as an adjunct to provide additional stability.

 
 
Table 44-5
Pearls and Pitfalls: Flexion-Type Teardrop Fractures
View Large
Table 44-5
Pearls and Pitfalls: Flexion-Type Teardrop Fractures
Pearls Pitfalls
Anterior corpectomy most useful surgical treatment Recognize subtle degrees of retrolisthesis (indicative of PLC disruption)
Preoperative reduction with GW tongs/halo ring can be helpful Avoid single-level anterior fusions in the presence of endplate involvement
Stand-alone posterior fixation can save a motion segment (considered in the neurologically intact patient only) Consider supplemental posterior fixation with severe preoperative kyphosis
 

GW, gardner wells; PLC, posterior ligamentous complex.

X
 
Figure 44-56
Most teardrop fractures are treated with anterior surgery.
 
In this case, a young woman presented with no neurologic deficits following a motor vehicle accident. A C6 vertebral body fracture is noted on plain films, with associated local kyphosis (A). Paramedian (B, D) and sagittal computed tomographic reconstructions (C) demonstrate the retrolisthesis of C6 on C7 as well as the gapping of the facet joints (white arrows). A magnetic resonance image (E) demonstrates no spinal cord compression. An anterior C6 corpectomy, followed by strut fusion with a cage and anterior plate stabilization was performed (F).
In this case, a young woman presented with no neurologic deficits following a motor vehicle accident. A C6 vertebral body fracture is noted on plain films, with associated local kyphosis (A). Paramedian (B, D) and sagittal computed tomographic reconstructions (C) demonstrate the retrolisthesis of C6 on C7 as well as the gapping of the facet joints (white arrows). A magnetic resonance image (E) demonstrates no spinal cord compression. An anterior C6 corpectomy, followed by strut fusion with a cage and anterior plate stabilization was performed (F).
View Original | Slide (.ppt)
Figure 44-56
Most teardrop fractures are treated with anterior surgery.
In this case, a young woman presented with no neurologic deficits following a motor vehicle accident. A C6 vertebral body fracture is noted on plain films, with associated local kyphosis (A). Paramedian (B, D) and sagittal computed tomographic reconstructions (C) demonstrate the retrolisthesis of C6 on C7 as well as the gapping of the facet joints (white arrows). A magnetic resonance image (E) demonstrates no spinal cord compression. An anterior C6 corpectomy, followed by strut fusion with a cage and anterior plate stabilization was performed (F).
In this case, a young woman presented with no neurologic deficits following a motor vehicle accident. A C6 vertebral body fracture is noted on plain films, with associated local kyphosis (A). Paramedian (B, D) and sagittal computed tomographic reconstructions (C) demonstrate the retrolisthesis of C6 on C7 as well as the gapping of the facet joints (white arrows). A magnetic resonance image (E) demonstrates no spinal cord compression. An anterior C6 corpectomy, followed by strut fusion with a cage and anterior plate stabilization was performed (F).
View Original | Slide (.ppt)
X
 
Results
 

Fisher et al.95 reported superior maintenance of alignment with anterior corpectomy, fusion, and plate stabilization as compared with halo vest immobilization when treating teardrop fractures. Others have also reported good results with anterior surgery for traumatic subaxial fractures, some of which included flexion teardrop injuries.2,30,199

 
Posterior Surgery
 
Indications
 

In rare cases, posterior surgery alone can be undertaken. This should be reserved for patients who are neurologically intact, have minimal vertebral body height loss, and have less than 30% of inferior endplate involvement. An advantage of this approach is that the fusion can potentially be restricted to a single motion segment.

 
Results
 

There are few reports of posterior surgery for flexion-type teardrop fractures. Among series of patients treated for a variety of subaxial cervical injuries, posterior stabilization with lateral mass screws has yielded acceptable outcomes.7,88,199

Authors’ Preferred Method of Treatment for Cervical Spine Fractures and Dislocations

 
 
Treatment Algorithm
 

It is the authors’ preference to treat the majority of flexion-type teardrop fractures operatively. This opinion is based on a strict definition of a teardrop fracture, defined as stage III, or greater, CF injuries as described by Allen et al.,5 in which disruption of the PLC is implied. Lesser flexion–compression injuries, more appropriately defined as cervical compression fractures, are addressed in that section.

 

Reduction of the kyphotic deformity is achieved via traction with cranial tongs. A moderate weight of 20 to 40 lb is generally sufficient. Traction can be applied prior to surgery, if a delay is anticipated, or intraoperatively once the patient has been positioned. With the exception of complete spinal cord injuries, neurologic monitoring is performed intraoperatively using evoked potentials. While traction is helpful, translational deformities are usually not fully reduced through the use of traction alone.

 

Apart from in a few selected cases, in which there is minimal deformity and canal compromise in a neurologically intact patient, anterior corpectomy, fusion, and stabilization are usually performed. The fractured vertebral body is removed to achieve canal decompression. A titanium mesh cage filled with salvaged autograft, supplemented by additional autograft or allograft, is then used to reconstruct the anterior column. An anterior cervical plate is applied for stabilization.

 

In most cases, anterior surgery is performed alone. The authors feel comfortable with this technique if reasonable lordosis has been restored, excellent screw purchase was achieved, and if the facet joints are reasonably well reduced following anterior surgery. Allen et al.5 stage III and IV injuries are usually adequately treated with an isolated anterior construct. With stage V injuries, in which there is marked translational deformity indicating substantial circumferential ligamentous injury, additional posterior stabilization and fusion is required.

 

Apart from common surgical complications related to the approach, decompression, or stabilization technique, there are few injury specific complications associated with the operative treatment of flexion-type teardrop fractures. Perhaps the most vexing is construct failure following isolated anterior surgery. The surgeon must be confident that the fixation method used will provide adequate stability until bony fusion occurs. After isolated posterior surgery, kyphotic deformity can result from settling of the fractured vertebral body, particularly with single-level constructs.

 
Facet Fractures without Dislocation
 
Diagnosis
 

Wide disagreement remains concerning the management of facet fractures without dislocation. The majority of fractures initially present as minimally displaced fractures (Fig. 44-57). Most can be treated nonoperatively with a rigid cervical collar without substantial late displacement (Table 44-6). However, in some cases, the fracture itself is not the essential lesion. Occult ligamentous disruption may also be present. Thus, MRI has played an increasingly important role in differentiating so-called stable and unstable facet fractures and may be an important tool in decision making regarding treatment (Fig. 44-58).

 
Figure 44-57
Lateral cervical radiograph of a minimally displaced articular process fracture.
 
In the authors’ experience, the majority of these injuries can be treated successfully in a hard cervical collar. Frequent follow-up radiographs should be obtained to detect late instability.
In the authors’ experience, the majority of these injuries can be treated successfully in a hard cervical collar. Frequent follow-up radiographs should be obtained to detect late instability.
View Original | Slide (.ppt)
Figure 44-57
Lateral cervical radiograph of a minimally displaced articular process fracture.
In the authors’ experience, the majority of these injuries can be treated successfully in a hard cervical collar. Frequent follow-up radiographs should be obtained to detect late instability.
In the authors’ experience, the majority of these injuries can be treated successfully in a hard cervical collar. Frequent follow-up radiographs should be obtained to detect late instability.
View Original | Slide (.ppt)
X
 
 
Table 44-6
Pearls and Pitfalls: Facet Fractures Without Dislocation
Pearls Pitfalls
Can usually be treated in a collar Late displacement, requires frequent radiographic follow-up
MRI useful in detecting concomitant ligamentous injuries Posterior stabilization leads to inferior radiographic results (kyphosis)
Recognize as a rotational injury Unrecognized ligamentous injury can lead to late displacement/dislocation and neurologic deterioration
 

MRI, magnetic resonance imaging.

X
 
Figure 44-58
Facet fracture treatment algorithm.
 
MRI, magnetic resonance imaging.
MRI, magnetic resonance imaging.
View Original | Slide (.ppt)
Figure 44-58
Facet fracture treatment algorithm.
MRI, magnetic resonance imaging.
MRI, magnetic resonance imaging.
View Original | Slide (.ppt)
X
 
Nonoperative Treatment
 
Indications
 

Most facet fractures are minimally displaced and can be considered mechanically stable. Patients with such injuries are treated in a rigid cervical collar for a period of 6 to 12 weeks, monitored by frequent radiographic examination. It is important to recognize, however, that these fractures may be associated with occult ligamentous injury although they may demonstrate little, if any, translational deformity at initial presentation. Many surgeons recommend routine MRI examination to rule out significant ligamentous damage in the presence of facet injuries. Disruption of the ALL and intervertebral disc is thought to play an important role in late displacement, although PLC injury can also occur. Neurologic injury associated with the fracture is rare and, if present, is usually limited to a mild single-root radiculopathy that often resolves without formal decompression. As isolated injuries, facet fractures score low on the SLIC and do not merit operative treatment.

 

Flexion–extension views should be obtained after the completion of collar immobilization to ensure stability. While late displacement is considered an indication of instability by most surgeons, it has been observed that autoarthrodesis may still occur with time. It is unclear what effect the long-term consequences of fixed deformity have on overall clinical results.

 
Results
 

In a retrospective review of unilateral facet injuries, most of which were facet fractures without dislocation, Dvorak et al.77 reported that nonoperative treatment resulted in inferior outcomes as compared with operative intervention. It is important to realize that there may have been a bias in favor of surgery in this study, as the nonoperative group consisted of only 18 patients compared with 72 who had surgical treatment, and conservative treatment may have been more common in patients who sustained more serious trauma to other regions or were the victims of polytrauma.

 
Operative Treatment
 
Anterior Surgery
 
Indications
 

Because of the inherent potential for ligamentous instability, some surgeons have aggressively recommended operative treatment of nearly all facet fractures. Others have focused their indications as a result of the judicious use of flexion–extension views or MRI. A validation study regarding the predictive value of MRI with respect to displacement of facet fractures has yet to be performed.

 

Either anterior or posterior surgery can be employed in the treatment of facet fractures. Anterior surgery usually consists of a single-level interbody fusion with a plate (Fig. 44-59). The advantages of this approach are that reported fusion rates are consistently high, infection rate is lower than that with posterior approaches,144 and the ability to fuse a single motion segment is preserved. It is important to choose the correct disc space for fusion This should be based on the facet joint involved, as opposed to the level of the articular process that is fractured.

 
Figure 44-59
 
If surgery is elected to stabilize a facet fracture, it is the authors’ preference to perform an anterior cervical discectomy and fusion.
If surgery is elected to stabilize a facet fracture, it is the authors’ preference to perform an anterior cervical discectomy and fusion.
View Original | Slide (.ppt)
Figure 44-59
If surgery is elected to stabilize a facet fracture, it is the authors’ preference to perform an anterior cervical discectomy and fusion.
If surgery is elected to stabilize a facet fracture, it is the authors’ preference to perform an anterior cervical discectomy and fusion.
View Original | Slide (.ppt)
X
 
Results
 

In the series published by Woodworth et al.,261 involving anterior fusion for posterior cervical injuries, some of the patients had facet fractures. This group reported a high fusion rate for the anterior technique, with mild or no disability based on the Neck Disability Index at the time of final evaluation. Similarly, Lifeso and Colucci155 reported superior outcomes for anterior as compared with posterior fusion in a cohort of patients, most of whom had unilateral articular process fractures. In this study, nearly 50% of the patients who underwent posterior interventions were found to exhibit late kyphosis or residual deformity.

 

To the best of our knowledge, the work of Kwon and colleagues144 remains the only prospective, randomized controlled trial to compare anterior and posterior surgical techniques for the treatment of unilateral facet injuries. These authors maintained that anterior fixation was associated with less postoperative pain, increased fusion rate, better maintenance of alignment, and a decreased risk of infection. Patient-based outcome measures revealed no significant difference between the two approaches.

 
Posterior Surgery
 
Indications
 

Posterior surgery entails stabilization and fusion and can be performed in a variety of ways. The most mechanically stable constructs are achieved with the use of bilateral lateral mass screws connected by rods. However, bilateral screw placement can be precluded with large articular process fractures, which require instrumentation of the next adjacent uninjured lateral mass. While these issues are avoided by using interspinous process wiring, the stability of the construct is inferior and contraindicated if lamina fractures are present. A combination construct, using an interspinous process wire and unilateral lateral mass instrumentation, is another option.

 
Results
 

As discussed earlier, both Kwon et al.144 and Lifeso and Colucci155 found posterior surgery to be inferior to anterior fusion for the treatment of facet fractures. While it is the authors’ preference to perform anterior surgery for these injuries, it is also accepted that modern posterior lateral mass instrumentation techniques can produce comparable radiographic and clinical results. One potential disadvantage of posterior lateral mass fixation is the frequent necessity to include an additional motion segment because of the inability to gain adequate screw purchase at the site of the facet fracture.

Authors’ Preferred Method of Treatment for Cervical Spine Fractures and Dislocations

 
 
Treatment Algorithm
 

The authors prefer to operatively treat isolated facet fractures with evidence of even mild displacement as potential translational injuries (Fig. 44-58). Translation of one vertebra on another implies that there is substantial injury to the intervertebral disc and/or ligamentous structures. Because of the risk of late subluxation, or frank facet dislocation, an anterior cervical discectomy, fusion, and plate stabilization are the preferred treatment. As the deformities are usually minor, reduction is easily achieved intraoperatively through plate application.

 

The authors’ treatment of nondisplaced facet fractures is more variable. In these cases, an MRI scan is obtained to determine whether the disc or ligamentous structures have been disrupted. If there is strong evidence of disc or ligamentous injury, operative treatment with anterior cervical discectomy and fusion is performed. If injury to these structures is not detected, or the MRI findings are equivocal, the awake, neurologically intact, and cooperative patient is fitted with a rigid cervical collar, and upright standing films are obtained. If alignment is maintained, integrity of the disc and ligaments is inferred. Surgery is performed if upright posture results in subluxation.

 
Complications
 

Complications are probably most common following nonoperative management of isolated facet fractures. In seemingly benign fractures, it is the integrity of the adjacent ligamentous structures that determines their stability. The authors have personally treated patients with late facet dislocations that occurred while they were being immobilized in a rigid cervical collar. In addition, late displacement can result in neurologic deterioration. As described earlier, posterior surgery cannot correct or maintain sagittal alignment as well as anterior surgery,144,155 although the clinical significance of this fact has not been determined.

 
Outcomes
 

There is little literature regarding the operative results of unilateral facet fractures. Because they are considered posterior rotational injuries, they are often reported in studies that group many posterior injuries together. Dvorak et al.77 reported that, even after surgical fixation, patients with facet injuries do not return to normal preinjury levels of bodily pain and function.

 
Facet Dislocations
 
Diagnosis
 

The treatment of facet subluxations and dislocations is not differentiated in the literature, probably because they represent stages of a continuum from facet capsule disruption to complete, bilateral facet dislocation. What is inconsistent with this continuum, as highlighted by Allen et al.,5 is that unilateral dislocations can occur without catastrophic PLC disruption, whereas bilateral facet subluxations, without frank dislocation, usually present with ligamentous disruption.

 
Nonoperative Treatment
 
Indications
 

The role of nonoperative treatment of facet dislocations is minimal. If nonoperative management is used, it should be reserved for unilateral facet dislocations in patients without any signs of neurologic injury or for those who are too sick to undergo surgery.

 
Results
 

Even in cases in which the patient is deemed suitable for nonoperative treatment, cervical orthoses are not usually considered adequate. The inability of halo-fixation to treat facet dislocations has also been demonstrated in the work of Sears and Fazl,215 with more than 50% of patients exhibiting persistent instability after treatment.

 

Frequent radiographic examination is important if nonoperative management is used. Evidence of autofusion of the dislocated facet joint or, less frequently across the disc space, is a sign of healing. After a course of 3 months of halo immobilization, the device should be removed and flexion–extension views obtained to confirm stability. Surgical fusion should be considered if instability persists. In cases in which stability has been achieved and no spinal cord injury is present, there is some risk of persistent, or late-onset radiculopathy, with unreduced unilateral facet dislocations.

 
Operative Treatment
 
Anterior Versus Posterior Surgery
 
Indications
 

The optimal means of treatment of unilateral or bilateral facet dislocations remains unclear. Several different approaches can be successful. It is important to recognize the limitations, advantages, and disadvantages of each. In certain circumstances, one treatment method may be preferred over another.

 

The safety of closed reduction as well as the role of MRI has been discussed previously. In brief, closed reduction appears to be a safe procedure in the awake, cooperative patient who can be serially examined. If the patient does not fulfill these criteria, particularly in those with incomplete spinal cord injury, prereduction MRI is strongly advised to detect the presence of a disc herniation (Table 44-7).

 
 
Table 44-7
Pearls and Pitfalls: Facet Dislocations
View Large
Table 44-7
Pearls and Pitfalls: Facet Dislocations
Pearls Pitfalls
Prereduction MRI in unexaminable patients Overcompression of posterior construct (may lead to disc extrusion)
If a herniated disc is present on postreduction MRI, anterior approach is advised Anterior stabilization alone prone to failure if endplates are fractured or facet joints overdistracted
Anterior approach may save motion segments if a facet fracture is present Avoid overdistraction when placing an anterior interbody graft
 

MRI, magnetic resonance imaging.

X
 

If closed reduction has been successful prior to surgery, an anterior or posterior fusion may be performed. There is no clear evidence of the superiority of one approach over the other. Posterior stabilization addresses the instability caused by ligamentous disruption more directly, but most surgeons are uncomfortable performing posterior surgery in the presence of a herniated disc, especially in a neurologically intact patient. Usually, anterior surgery is initially undertaken to remove the herniated disc. The authors believe that anterior surgery is indicated if the spinal cord is being compressed by a disc herniation following reduction.

 
Posterior Surgery
 

Posterior surgery can be an effective means of surgical stabilization of any facet dislocation. Proponents of this method emphasize that posterior fixation most closely addresses the primary injury site, which is the posterior tension band. Care must be taken, however, if herniated disc fragments are present. Some surgeons consider this to be a contraindication to posterior surgery,83 particularly in the presence of a spinal cord injury. Disc herniations can be increased because of posterior compression applied through screws or wires. Nonetheless, posterior surgery is the most effective approach for open reduction of facet dislocations.218 The posterior approach is also usually preferred in instances of late, or chronic, dislocation.

 
Anterior Surgery
 

While most facet dislocations can be treated through either anterior or posterior methods, most surgeons would consider a large herniated disc following a closed reduction to be an indication for anterior decompression. In addition, advocates of prereduction MRI feel strongly that anterior surgery should be performed initially if a herniated disc fragment is present. Open reduction of a facet dislocation can be achieved anteriorly, although this is more difficult than when the posterior approach is used. If an anterior fusion is performed, it is incumbent upon the surgeon to make sure that there is no facet widening at the end of the procedure, such that the integrity of the anterior construct will be put at risk. Using a trapezoidal graft and contouring the plate into lordosis have been recommended as a means to increase stability when using anterior surgery to treat facet dislocations.78

 
Combined Approach
 

Combined anterior and posterior surgery may also be performed (Fig. 44-60). This is usually reserved for patients with more severe, or missed, injuries associated with fixed deformities. It is the authors’ preference to perform anterior surgery followed by posterior stabilization for patients with highly unstable bilateral facet dislocations. If the facets are gapped or kyphosis remains after anterior surgery, posterior instrumentation is performed to avoid catastrophic construct failure. Combined anterior–posterior surgery is rarely necessary for unilateral dislocations.

 
Figure 44-60
 
Paramedian (A, C) and sagittal (B) computed tomographic reconstructions of a patient who sustained a unilateral facet fracture–dislocation with contralateral facet subluxation (white arrow). As the patient was awake and examinable, he underwent a closed reduction. A postreduction magnetic resonance image demonstrates adequate canal decompression and no evidence of residual herniated disc (D).
Paramedian (A, C) and sagittal (B) computed tomographic reconstructions of a patient who sustained a unilateral facet fracture–dislocation with contralateral facet subluxation (white arrow). As the patient was awake and examinable, he underwent a closed reduction. A postreduction magnetic resonance image demonstrates adequate canal decompression and no evidence of residual herniated disc (D).
View Original | Slide (.ppt)
Figure 44-60
Paramedian (A, C) and sagittal (B) computed tomographic reconstructions of a patient who sustained a unilateral facet fracture–dislocation with contralateral facet subluxation (white arrow). As the patient was awake and examinable, he underwent a closed reduction. A postreduction magnetic resonance image demonstrates adequate canal decompression and no evidence of residual herniated disc (D).
Paramedian (A, C) and sagittal (B) computed tomographic reconstructions of a patient who sustained a unilateral facet fracture–dislocation with contralateral facet subluxation (white arrow). As the patient was awake and examinable, he underwent a closed reduction. A postreduction magnetic resonance image demonstrates adequate canal decompression and no evidence of residual herniated disc (D).
View Original | Slide (.ppt)
X
 
Results
 

Feldborg Nielson et al.92 reported that anterior fusion resulted in better pain relief than posterior wiring without fusion for facet dislocations. These authors attributed this to persistent residual motion in the unfused cases. Razack et al.194 performed single-level anterior fusion with a titanium locking plate in 22 patients with bilateral facet fracture dislocations. At an average follow-up of 32 months, only one case of instrumentation failure was reported, although all patients eventually achieved solid fusion and stability. Vital et al.252 maintained that, in a cohort of 91 bilateral facet dislocations, anterior surgical maneuvers were required to obtain a reduction in 27% of cases. Anterior discectomy and plate fixation was performed in all patients as definitive treatment. However, it should be noted that several patients developed new neurologic deficits following reduction.

 

Shapiro reported218 outcomes in a series of 24 patients treated for unilateral facet dislocations. Although halo fixation was attempted in two patients who had undergone successful closed reduction, recurrent dislocations occurred in both cases and surgery was eventually performed. Fusion was successful in 96% of the study population. In a follow-up analysis,218 comparable clinical results were reported with interspinous wiring and lateral mass fixation as compared with facet wiring with iliac crest bone graft. Better maintenance of sagittal correction was observed in the group treated with lateral mass instrumentation. In a review of their cases, Beyer et al22 found that unilateral facet dislocations or fracture–dislocations were better treated operatively, as nonoperative management led to an unacceptably high rate of chronic pain and late instability.

 
Complications
 

There are disadvantages to both anterior and posterior techniques. Anterior discectomy and fusion involves resection of one of the major remaining stabilizing structures, the ALL. Because of this, one can easily overdistract the disc space during placement of interbody grafts. This can leave the facet joints gapped posteriorly, which may alter posterior column load sharing. Improper fit of the interbody device can also place greater demands on the anterior plate and screws, resulting in early hardware failure.

 

With posterior instrumentation, and, in particular, the placement of lateral mass screws, injury to the adjacent intact facet joints can occur. While posterior compression can aid in articular apposition, overcompression can increase intradiscal pressure. This can cause intraoperative disc herniations that can cause further neurologic injury. Intraoperative spinal cord monitoring is useful in these situations.

Authors’ Preferred Method of Treatment for Cervical Spine Fractures and Dislocations

 
 
Treatment Algorithm
 

It is the authors’ preference to attempt a closed reduction using cranial tongs or halo traction as early as possible in patients who are awake, conscious, and able to be serially examined (Fig. 44-61). This is executed on an emergent or urgent basis as it influences the need for canal decompression. In the authors’ hands, reduction is performed regardless of neurologic status or the presence of a herniated disc fragment. As there is no compelling evidence to suggest that closed reduction in an awake, examinable patient can cause neurologic deterioration, it is the authors’ experience that performing surgery, either via an anterior or posterior approach, is easier if reduction can be achieved prior to surgery.

 
Figure 44-61
Facet dislocation treatment algorithm.
 
Note that the algorithm is constructed with the assumption that the patient is awake, alert, and can be serially examined. MRI, magnetic resonance imaging.
Note that the algorithm is constructed with the assumption that the patient is awake, alert, and can be serially examined. MRI, magnetic resonance imaging.
View Original | Slide (.ppt)
Figure 44-61
Facet dislocation treatment algorithm.
Note that the algorithm is constructed with the assumption that the patient is awake, alert, and can be serially examined. MRI, magnetic resonance imaging.
Note that the algorithm is constructed with the assumption that the patient is awake, alert, and can be serially examined. MRI, magnetic resonance imaging.
View Original | Slide (.ppt)
X
 

Although the authors have a strong bias toward anterior surgery for facet dislocations, a postreduction MRI scan is obtained if possible. Most would agree that the information yielded from a postreduction MRI scan can influence how, and if, posterior surgery will be executed should a herniated disc fragment be present. Although the disc is routinely removed during anterior surgery, the postreduction MRI can be helpful in identifying the location of the herniated fragments, which may be located behind the vertebral body. In these cases, corpectomy might be elected instead of a single-level discectomy to ensure full canal decompression.

 

Anterior discectomy and fusion is performed as described earlier. It is the authors’ preference to use a titanium mesh cage filled with autograft or allograft. A cage that is 7 or 8 mm in height is usually adequate. After placement of the cage, the head is axially loaded to maximize endplate engagement with the cage. This maneuver also helps avoid facet gapping.

 

Next, a plate is applied. While some recommend fixed angle plating, the authors utilize a semirigid plate that allows a small amount of angular toggle of the screw heads in the plate holes. Plates with slotted screw holes and axially dynamic plates should be avoided in surgery for traumatic instability.

 

If a reduction cannot be achieved by closed means, a MRI scan is obtained to assess for disc herniation. If no herniation is present, the patient may be taken to the operating room for open reduction and instrumented fusion from a posterior approach. If a disc fragment is present anteriorly, the disc should initially be removed through an anterior approach. If reduction still cannot be achieved after disc excision, the patient may have to be turned posteriorly and an open reduction and fusion performed. The patient can then be returned to the supine position, and the anterior fusion completed using cage and plate fixation.

 

Following anterior surgery, high-quality intraoperative fluoroscopic images are obtained to assess the integrity of the facet joints. If the joint surfaces appear to be overly distracted, this being particularly common with bilateral facet dislocations and exceedingly uncommon with unilateral injuries, single-level posterior lateral mass fixation and fusion is performed as a second stage during the same operation. Postoperatively, patients are mobilized as tolerated. A rigid cervical collar is maintained for 6 to 8 weeks. Regular radiographs are obtained to assess alignment and bone healing.

 
Miscellaneous Injuries
 
Pedicle and Lamina Fractures
 

Unilateral pedicle fractures are usually considered to be rotational injuries. For this reason, their evaluation and treatment is similar to that of unilateral facet fractures. Bilateral pedicle fractures may be a sign of higher-energy injury. A high index of suspicion for unstable ligamentous discontinuity should be maintained if such a pattern is present.

 

Lamina fractures, by themselves, are usually benign. However, they are often associated with other more significant fractures. Multilevel lamina fractures can also suggest a hyperextension injury. Careful inspection of the uniformity of the disc spaces and the integrity of the ALL on MRI should be used to detect disruption of the anterior tension band.

 
Anterior Tension Band Injuries
 

Disruption of the ALL can be associated with innocuous vertebral body fractures, these usually being avulsion injuries near the anterior endplate.81 Abnormal widening at the disc space is the clue to diagnosis (Fig. 44-51). Extension injuries that disrupt the ALL can also be associated with posterior fractures or circumferential ligamentous disruption, in which case sagittal and coronal malalignment is present.

 

Anterior tension band injuries should be considered to be unstable. Because of this, nonoperative treatment is rarely considered to be an appropriate definitive management. In cases in which the patient is too sick to undergo surgery, a halo device can be applied as a temporizing measure. Provided the posterior tension band, including the facet capsule, is intact, a flexion force can reapproximate the vertebral bodies. If reduction can be maintained, ankylosis of the disc space can occur with time. Flexion–extension views must be obtained to confirm adequate stability following immobilization.

 

Anterior tension band disruption, consisting of discontinuity of the ALL and intervertebral disc is, almost always, an indication for anterior surgery. An anterior discectomy and plating with fusion can restore the mechanics of the tension band just as posterior fixation address posterior ligamentous disruption with facet dislocations. To the authors’ knowledge, there are no series investigating the results of surgical fixation for anterior tension band injuries. As the proposed mechanism is similar, extension-type cervical teardrop fractures can also be managed with either anterior or posterior operative technique.

 
Cervical Injuries of the Ankylosed and Spondylotic Spine
 

Individuals with diffusely ankylosed spines, regardless of the underlying pathology, have often been considered as a single group when discussing cervical trauma, although this may not be entirely appropriate.212 Although the underlying pathologies differ, AS, DISH, and severe osteoarthritic ankylosis all result in a rigid, immobile, spine that may be exceedingly prone to fracture and functions more like a long bone if injured.

 

Where there is known hyperostotic disease, patients who present with neck pain and/or neurologic deficit after major, or minor, trauma should be considered to have a cervical spine injury until proven otherwise. Degenerative spondylotic changes, such as vertebral body osteophytes, fixed subluxations, and facet hypertrophy, can make the radiographic diagnosis of fracture difficult. Unless a frank dislocation, or a translational or intervertebral extension deformity is present, plain radiographs may not be helpful in identifying an injury. In patients with hyperostotic disease, computed tomography and MRI are invaluable in delineating injuries. MRI also has the additional advantages of demonstrating spinal cord contusion, cord edema, and epidural hematoma.

 

When considering treatment options, the ankylosed spine should be considered as a long bone rather than the normal spinal column with individually articulating vertebrae. Bridging osteophytes, whether marginal, as in AS (Fig. 44-62), or nonmarginal as in DISH, are the radiographic characteristics of the hyperostotic spine. The condition effectively fuses the spine into a solid, continuous piece of bone that generally sustains extensile injuries that traverse the anterior and posterior elements.212,256 Thus, fractures in patients with DISH or AS are almost universally unstable and should be treated as such.

 
Figure 44-62
 
Lateral cervical radiograph of a patient with ankylosing spondylitis who was complaining of neck pain after a fall 2 days prior to presentation (A). Note the radiographic hallmarks of marginal bridging osteophytes. Also note that this single lateral radiograph is inadequate, as it does not allow visualization of the cervicothoracic unction. This is best seen on computed tomographic scan (B), which demonstrates a fracture through the ossified disc space. A magnetic resonance image (C) confirms the presence of increased signal in the region. Staged posterior and anterior surgery was performed. Note the reverse contouring of the anterior plate (D).
Lateral cervical radiograph of a patient with ankylosing spondylitis who was complaining of neck pain after a fall 2 days prior to presentation (A). Note the radiographic hallmarks of marginal bridging osteophytes. Also note that this single lateral radiograph is inadequate, as it does not allow visualization of the cervicothoracic unction. This is best seen on computed tomographic scan (B), which demonstrates a fracture through the ossified disc space. A magnetic resonance image (C) confirms the presence of increased signal in the region. Staged posterior and anterior surgery was performed. Note the reverse contouring of the anterior plate (D).
View Original | Slide (.ppt)
Figure 44-62
Lateral cervical radiograph of a patient with ankylosing spondylitis who was complaining of neck pain after a fall 2 days prior to presentation (A). Note the radiographic hallmarks of marginal bridging osteophytes. Also note that this single lateral radiograph is inadequate, as it does not allow visualization of the cervicothoracic unction. This is best seen on computed tomographic scan (B), which demonstrates a fracture through the ossified disc space. A magnetic resonance image (C) confirms the presence of increased signal in the region. Staged posterior and anterior surgery was performed. Note the reverse contouring of the anterior plate (D).
Lateral cervical radiograph of a patient with ankylosing spondylitis who was complaining of neck pain after a fall 2 days prior to presentation (A). Note the radiographic hallmarks of marginal bridging osteophytes. Also note that this single lateral radiograph is inadequate, as it does not allow visualization of the cervicothoracic unction. This is best seen on computed tomographic scan (B), which demonstrates a fracture through the ossified disc space. A magnetic resonance image (C) confirms the presence of increased signal in the region. Staged posterior and anterior surgery was performed. Note the reverse contouring of the anterior plate (D).
View Original | Slide (.ppt)
X
 

The key to caring for patients with cervical fractures and DISH or AS is early recognition of the injury to avoid catastrophic neurologic decline. Diagnosis has been frequently missed in the past, resulting in a very high rate of neurologic deficits in previously normal patients. AS has been demonstrated to be a significant risk factor for neurologic decline in all cervical fractures.61,82 A sudden increase in kyphosis and decrease in horizontal forward gaze is a common feature with acute fractures in patients with AS. Patients should be immobilized in their normal preinjury position, which may include a certain degree of kyphosis in those with AS, as soon as the diagnosis is made. They should then be admitted to the hospital, and placed on a strict logroll regimen until the definitive approach to treatment has been determined. Patients with AS, particularly following injury, are also predisposed to developing neurologic decline from epidural hematomata.

 

Very few studies are available that provide data of sufficient value to provide treatment recommendations for these injuries. Older studies reported the effective use of halo fixation.107 However, the results are suboptimal when compared with modern spinal instrumentation techniques, and mortality rates in the elderly have been found to be high following halo immobilization.256 Long posterior constructs have been advocated as well,228 with some surgeons proposing combined anterior–posterior instrumentation as the ideal surgical treatment.82

 

Key principles in management should be applied in every instance, regardless of the surgical approach. As mentioned previously, when placing patients in traction, any preexisting kyphotic deformity must be considered. Thus, inline traction, as is effectively used for most other cervical injuries, can lead to catastrophic neurologic compromise. The awake, cooperative, patient should help determine the position of comfort when applying traction. In cases of AS, a kyphosis usually necessitates a flexion force being applied.

 

This same concept is important when considering operative fixation. Both anterior and posterior implants should be contoured to fit the patients’ specific anatomy. Unless an osteotomy is planned during the intervention, internal fixation of the fracture should maintain, or approximate, the preinjury posture of the neck. This may require unusual implant contouring.

 

Preoperative discussion with patients and their families should take into account the high complication and mortality rates that have been reported in association with traumatic injuries to the hyperostotic spine.212,228,256 Acute mortality rates have ranged from 17% to 30%,107,212,228,256 with similar percentages of perioperative morbidity being published.256 Whang et al.256 reported a 50% mortality rate for patients with AS at 2 years postinjury. In a study that investigated the relationship between mortality and time in patients with AS and DISH, Schoenfeld and coworkers212 documented a 38% mortality for those with AS at 3 months and 63% by 1 year. In this study, patients with AS demonstrated a statistically increased mortality when compared to age-, sex-, and injury-matched controls. This was not seen in patients with DISH, leading the authors to conclude that these diseases should not be considered a homogeneous group when evaluating outcomes.212

 
Spinal Cord Injury without Instability in the Spondylotic Spine
 

A traumatic spinal cord injury, without instability, in the spondylotic or congenitally stenotic spine is most usually central cord syndrome. The pathophysiology of this condition has been discussed previously. Classically, the physical manifestations include motor, as well as sensory, deficits, with the upper extremities being affected to a greater extent than the lower extremities. However, patients may exhibit varying degrees of compromise of lower extremity function, as well as bowel or bladder dysfunction. Patients often present with complete, or incomplete, spinal cord injury without radiographic signs of a frank injury, fracture, or ligamentous disruption. Underlying cervical stenosis is often present, which can arise from degenerative changes or a congenitally narrow canal (Fig. 44-63). This apparently increases the risk of neural injury with abrupt movements of the neck that otherwise are not severe enough to result in a significant fracture or ligament injury.

 
Figure 44-63
 
Magnetic resonance image of a 55-year-old man who presented with weakness that was greater in the upper extremity than in the lower extremity consistent, with a central cord syndrome (A). A computed tomographic scan did not demonstrate any bony injuries or misalignment (B). After a period of observation during which the patient’s neurologic status had reached a plateau, a posterior laminectomy and fusion was performed in order to hasten his neurologic recovery (C, D).
Magnetic resonance image of a 55-year-old man who presented with weakness that was greater in the upper extremity than in the lower extremity consistent, with a central cord syndrome (A). A computed tomographic scan did not demonstrate any bony injuries or misalignment (B). After a period of observation during which the patient’s neurologic status had reached a plateau, a posterior laminectomy and fusion was performed in order to hasten his neurologic recovery (C, D).
View Original | Slide (.ppt)
Figure 44-63
Magnetic resonance image of a 55-year-old man who presented with weakness that was greater in the upper extremity than in the lower extremity consistent, with a central cord syndrome (A). A computed tomographic scan did not demonstrate any bony injuries or misalignment (B). After a period of observation during which the patient’s neurologic status had reached a plateau, a posterior laminectomy and fusion was performed in order to hasten his neurologic recovery (C, D).
Magnetic resonance image of a 55-year-old man who presented with weakness that was greater in the upper extremity than in the lower extremity consistent, with a central cord syndrome (A). A computed tomographic scan did not demonstrate any bony injuries or misalignment (B). After a period of observation during which the patient’s neurologic status had reached a plateau, a posterior laminectomy and fusion was performed in order to hasten his neurologic recovery (C, D).
View Original | Slide (.ppt)
X
 

There are limited data regarding the best treatment or optimal time period for intervention. Nonoperative management can include a period of observation, mainly for patients with central cord lesions, because many patients will have virtually complete resolution of their neural deficits.180 Some authors, such as Fehlings and Arvin,87 emphasize that central cord syndrome is an incomplete spinal cord injury, and early decompression may increase the chances of complete recovery. If initial management consists of immobilization and patient observation, long-term treatment is influenced by the presence of persistent symptoms of myelopathy. Young age, higher level of education, absence of cord signal anomalies, motor function at presentation, and absence of spasticity have all been cited as good prognostic indicators of outcome, whereas medical comorbidities, instability, and a high degree of spinal canal compromise were identified as predictors of inferior results.180

 

In a retrospective study, Chen et al.55 maintained that early surgery resulted in faster neurologic recovery, with better motor scores at 1 and 6 months after surgery. By 2 years, however, there was no statistically significant difference between the operative and nonoperative groups. Guest et al.113 had similar findings, and they proposed that surgery within 24 hours of traumatically induced central cord syndrome was safe and more cost-effective than delayed procedures.

 

More recently, Chen and coworkers54 reviewed outcomes following surgical intervention for central cord syndrome based on the timing of intervention. They designated surgery performed within 4 days of the injury as early surgery. In this investigation, no significant difference in outcome was reported between those who received early surgery or delayed surgery. The surgical approach and the underlying cervical pathology, such as traumatic disc herniation, fracture, or spondylosis, also did not influence outcome. However, these authors did document that even after surgical intervention, physical function scores do not improve to the same extent as motor function and sensation.54 Moreover, almost a third of the cohort was dissatisfied with their final functional outcome. Such findings led Fehlings and Arvin87 to call for more aggressive intervention for central cord syndrome, pointing out that the definition of early surgery in the work of Chen et al.54 did not meet the Spine Trauma Study Group criteria of intervention performed within 24 hours of injury.

 

In the authors’ practice, operative treatment is delayed. Following resolution of spinal shock, patients are observed for signs of neurologic recovery over a period of 2 to 3 days. If there are no signs of return of function, surgical decompression is performed in the hope of improving the rate of recovery. Surgery is postponed if physical examination demonstrates improvement in motor strength. Many patients will have complete motor and sensory recovery but demonstrate residual signs and symptoms of myelopathy, such as walking imbalance or diminished finger dexterity. If this occurs, a decompressive procedure is performed, electively, in the weeks following injury.

 
Gunshot Wounds to the Cervical Spine
 

There is little information about cervical gunshot wounds.32 Important details at the time of presentation include the type of weapon responsible for the injury, the trajectory of the gunshot wound, associated visceral injuries, location of the bullet or fragments, and the presence of neurologic injury. Low-velocity gunshot wounds, such as those caused by a pistol, cause less soft-tissue damage and do not necessarily equate with an open fracture. They are also less likely to cause unstable spinal injuries, even if the fracture has occurred in anterior and posterior elements of the cervical spine. The column-concept of spinal trauma, as devised for high-energy mechanisms, has no place in the consideration of injuries caused by gunshot.

 

High-velocity wounds, such as those caused by automatic rifles, explosive blasts, and shrapnel injuries, also cause extensive soft-tissue trauma, and the treatment should be more aggressive, akin to open injuries. In a series involving penetrating cervical injuries in a military setting, Ramasamy et al.192 reported a 0% survival rate for high-velocity penetrating injuries of the cervical region associated with spinal instability. However, cervical spine injuries were present only in approximately a quarter of all those sustaining penetrating neck wounds. In a similar series from the United States, Vanderlan et al.247 documented that the incidence of neurologic injury following gunshot wound to the cervical region was 17.5%.

 

Kupcha et al.143 reviewed the records of 28 patients who sustained gunshot wounds to the cervical spine. Laminectomy was performed in four patients and anterior corpectomy in one, with no difference in neurologic improvement compared with the cases that did not undergo decompression. Neck exploration was undertaken for vascular damage in four cases, expanding hematoma in two cases, and airway difficulty in three cases. Long-term complications were primarily related to thromboembolic disease, pulmonary congestion, and urinary tract infection. Posttraumatic syrinx developed in two patients. Despite a lack of description regarding antibiotic regimen, only one case of meningitis was reported. From these limited data, it seems that the care of cervical gunshot wounds should be guided by the principles used in other regions of the body.32

 

Decompression, or bullet removal, in cervical spinal cord injury is probably not useful for static neural deficits, while it may be beneficial in cases of neurologic deterioration when there is obvious compression of the spinal cord. Laminectomy can be useful but should be accompanied by appropriate instrumentation and fusion.32 The decision to surgically explore neck wounds should be dictated by the severity of extraspinal injuries.

 

Extended antibiotic prophylaxis is prudent after pharyngeal, hypopharyngeal, or airway violations. However, the role of antibiotic prophylaxis after esophageal and upper airway perforation is not well defined. Pooled secretions in the hypopharynx are thought to increase the risk of infection if the gunshot wound involves this area. The decision to explore such wounds is usually based on the size of the lesion, as small wounds can effectively be treated nonoperatively. To the authors’ knowledge, there are no controlled studies regarding the impact of antibiotic prophylaxis following gunshot injuries of the upper airway. Because of the potential for frank infection or meningitis, it is prudent to extend prophylaxis for at least 48 to 72 hours. Delayed exploration for developing neck infections is also recommended, although the role of cervical gunshot wound debridement remains to be clarified.

 
Vertebral Artery Injury in Association with Cervical Trauma
 

The vertebral artery within the subaxial spine can be injured as a result of trauma. The mechanism of injury can be laceration, distractive avulsion, or intimal injury resulting in occlusion. Vertebral artery injury can occur with fractures of the transverse processes, through which the vertebral artery passes. Magnetic resonance arteriograms are an effective means of noninvasive diagnosis of vertebral artery occlusion, or narrowing, following cervical trauma. Formal dye-injection arteriography is another option.

 

The incidence of vertebral artery injury following lower cervical spine trauma has been reported to be as high as 25% to 46%.98,188,260 Such injuries have occurred with facet dislocations, facet fractures with translation, and transverse foramen fractures.202,260 The vast majority of injuries are unilateral, which fortunately have a very low rate of clinical sequelae. In most cases, no specific treatment is necessary. However, the detection of the injury can have an important influence on overall treatment decision making. The surgeon must consider the consequences of surgical techniques that might damage the remaining intact vertebral artery, such as lateral mass screw placement or C1–C2 transarticular screw insertion. It may be prudent to avoid such procedures on the unaffected side, which can potentially lead to bilateral vertebral artery compromise.

 

In a series of eight patients with unilateral vertebral artery injury in the setting of subaxial cervical fractures, Sack et al.202 performed surgical interventions, with the majority of patients receiving no specific treatment of the arterial injury. Three patients were treated with aspirin therapy. Posterior fusion was performed in seven of the eight patients, although the authors do not detail whether instrumentation was placed on the side of the uninjured vertebral artery. No ischemic complications were reported.

 

Bilateral vertebral artery injuries can be devastating, resulting in cerebellar infarction. This has been reported in patients with severe dislocations of the subaxial cervical spine.170 Such injuries necessitate emergent recanalization using pharmacologic or angiographic techniques.

 
C7 Spinous Process (Clay-Shoveler’s Fractures)
 

As a stand-alone injury, lower spinous process fractures are usually benign entities. The so-called clay-shoveler’s fracture is thought to occur from powerful contraction of the back muscles that insert onto the spinous process. However, spinous process fractures can also occur in conjunction with lamina fractures, facet dislocations, and other more serious injuries. An early report described spinous process fractures that present in association with bilateral lamina fractures as an indication of potential neurologic deterioration.167 It is thought that the floating posterior arch can displace anteriorly, impinging on the spinal canal.

Controversies and Future Directions for Cervical Spine Fractures and Dislocations

It is interesting to observe that many of the controversies that have challenged spine surgeons over the last 10 to 15 years still remain unanswered. Despite remarkable advances in surgical instrumentation, the use of biologics, and in our understanding of the pathophysiologic processes of trauma, the scope of practice has remained largely unaltered in the last decade. Decompression, stabilization, and the avoidance and treatment of neurologic injury remain the focus of surgeons who treat the victims of spinal trauma, and these tenets are hardly different from those espoused by the practitioners who composed the Edwin Smith Surgical Papyrus. 
The challenges that confront the spine surgical community as a whole are largely due to a paucity of scientifically rigorous data and cost-effectiveness analyses of available treatment options. Many of the purported advantages of spine trauma surgery, while well accepted, remain unsupported by high-quality evidence. This includes the recommendation for surgical intervention within 24 hours of spinal cord injury, although the forthcoming results of the Surgical Treatment of Acute Spinal Cord Injury Study may go a long way to ameliorate this. 
The nature of spinal trauma precludes many types of systematic investigation, such as prospective randomized trials, that are available to other fields of spine surgery, and inferences from studies involving degenerative conditions are not necessarily applicable to trauma. The roles that age, medical comorbidities, and approaches to surgical intervention play in survival and function after spine trauma are not especially clear, and this is especially important when one considers the aging population and the increased levels of activity undertaken by the elderly today. Optimal outcome measures remain to be defined, with many authors postulating that the bodily pain scales and physical function scores that are well established for degenerative conditions are not valid in trauma studies. Unfortunately, we do not, as yet, know which are the best outcome measures, which factors influence survival in the acute period, and how can we best maximize neurologic recovery. 
With many of these challenges coming to the fore within the last 4 to 5 years, it is hoped that spine surgeons will work to develop their own literature base in a scientifically rigorous fashion, such that at least some of these questions can be answered to the fullest extent possible. Certainly, the continued efforts of the Spine Trauma Study Group to develop guidelines are encouraging in this respect. It is anticipated that progress in the management of spinal trauma will undoubtedly expand the horizons of care for the injured in what is already the sixth millennium of human experience with spinal trauma. 

References

1.
Aebi M, Etter C, Coscia M. Fractures of the odontoid process. Treatment with anterior screw fixation. Spine. 1989;14:1065–1070.
2.
Aebi M, Zuber K, Marchesi D. Treatment of cervical spine injuries with anterior plating. Indications, techniques, and results. Spine. 1991;16:S38–S45.
3.
Agabegi SS, Asghar FA, Herkowitz HN. Spinal orthoses. J Am Acad Orthop Surg. 2010;18:657–667.
4.
Alfieri A. Single-screw fixation for acute type II odontoid fracture. J Neurosurg Sci. 2001;45:15–18.
5.
Allen B, Ferguson R, Lehmann T, et al. A mechanistic classification of closed, indirect fractures and dislocations of the lower cervical spine. Spine. 1982;7:1982.
6.
Ames CP, Bozkus MH, Chamberlain RH, et al. Biomechanics of stabilization after cervicothoracic compression-flexion injury. Spine. 2005;30:1505–1512.
7.
An HS, Coppes MS. Posterior cervical fixation for fracture and degenerative disc disease. Clin Orthop Relat Res. 1997;335:101–111.
8.
Anderson AJ, Towns GM, Chiverton N. Traumatic occipitocervical disruption: A new technique for stabilisation. Case report and literature review. J Bone Joint Surg Br. 2006;88:1464–1468.
9.
Anderson LD, D’Alonzo RT. Fractures of the odontoid process of the axis. J Bone Joint Surg Am. 1974;56:1663–1674.
10.
Anderson PA, Gugala Z, Lindsey RW, et al. Clearing the cervical spine in the blunt trauma patient. J Am Acad Orthop Surg. 2010;18:149–159.
11.
Anderson PA, Montesano PX. Morphology and treatment of occipital condyle fractures. Spine. 1988;13:731–736.
12.
Anderson PA, Moore TA, Davis KW, et al. Cervical spine injury severity score. Assessment of reliability. J Bone Joint Surg Am. 2007;89:1057–1065.
13.
Andersson S, Rodrigues M, Olerud C. Odontoid fractures: High complication rate associated with anterior screw fixation in the elderly. Eur Spine J. 2000;9:56–59.
14.
Andreshak JL, Dekutoski MB. Management of unilateral facet dislocations: A review of the literature. Orthopedics. 1997;20:917–926.
15.
Askins V, Eismont FJ. Efficacy of five cervical orthoses in restricting cervical motion: A comparison study. Spine. 1997;22:1193–1198.
16.
Aulino JM, Tutt LK, Kaye JJ, et al. Occipital condyle fractures: clinical presentation and imaging findings in 76 patients. Emerg Radiol. 2005;11:342–347.
17.
Baaj AA, Uribe JS, Nichols TA, et al. Health care burden of cervical spine fractures in the United States: analysis of a nationwide database over a 10-year period. J Neurosurg Spine. 2010;13:61–66.
18.
Barros Filho TE, Oliveira RP, Grave JM, et al. Corpectomy and anterior plating in cervical spine fractures with tetraplegia. Rev Paul Med. 1993;111:375–377.
19.
Battaglia TC, Tannoury T, Crowl AC, et al. A cadaveric study comparing standard fluoroscopy with fluoroscopy-based computer navigation for screw fixation of the odontoid. J Surg Orthop Adv. 2005;14:175–180.
20.
Beckner MA, Heggeness MH, Doherty BJ. A biomechanical study of Jefferson fractures. Spine. 1998;23:1832–1836.
21.
Bellabarba C, Mirza SK, West GA, et al. Diagnosis and treatment of craniocervical dislocation in a series of 17 consecutive survivors during an 8-year period. J Neurosurg Spine. 2006;4:429–440.
22.
Beyer CA, Cabanela ME, Berquist TH. Unilateral facet dislocations and fracture-dislocations of the cervical spine. J Bone Joint Surg Br. 1991;73:977–981.
23.
Bhanot A, Sawhney G, Kaushal R, et al. Management of odontoid fractures with anterior screw fixation. J Surg Orthop Adv. 2006;15:38–42.
24.
Bivins HG, Ford S, Bezmalinovic Z, et al. The effect of axial traction during orotracheal intubation of the trauma victim with an unstable cervical spine. Ann Emerg Med. 1989;17:25–29.
25.
Blacksin MF, Lee HJ. Frequency and significance of fractures of the upper cervical spine detected by CT in patients with severe neck trauma. AJR Am J Roentgenol. 1995;165:1201–1204.
26.
Blauth M, Richter M, Kiesewetter B, et al. [Operative versus non operative treatment of odontoid non unions. How dangerous is it not to stabilize a non union of the dens?]. Chirurg. 1999;70:1225–1238.
27.
Bloom AI, Neeman Z, Slasky BS, et al. Fracture of the occipital condyles and associated craniocervical ligament injury: Incidence, CT imaging and implications. Clin Radiol. 1997;52:198–202.
28.
Blumberg KD, Catalano JB, Cotler JM, et al. The pullout strength of titanium alloy MRI-compatible and stainless steel MRI-incompatible Gardner-Wells tongs. Spine. 1993;18:1895–1896.
29.
Boakye M, Patil CG, Santarelli J, et al. Cervical spondylotic myelopathy: Complications and outcomes after spinal fusion. Neurosurgery. 2008;65:455–462.
30.
Bohler J, Gaudernak T. Anterior plate stabilization for fracture-dislocations of the lower cervical spine. J Trauma. 1980;20:203–205.
31.
Bono CM. The halo fixator. J Am Acad Orthop Surg. 2007;15:728–737.
32.
Bono CM, Heary RF. Gunshot wounds to the spine. Spine J. 2004;4:230–240.
33.
Bono CM, Schoenfeld AJ, Anderson PA, et al. Observer variability of radiographic measurements of C2 (axis) fractures. Spine. 2010;35:1206–1210.
34.
Bono CM, Schoenfeld A, Gupta G, et al. Reliability and reproducibility of subaxial cervical injury description system: A standardized nomenclature schema. Spine. 2011;36:E1140–E1144.
35.
Bono CM, Schoenfeld A, Rampersaud R, et al. Reproducibility of radiographic measurements for subaxial cervical spine trauma. Spine. 2011;36:1374–1379.
36.
Bono CM, Vaccaro AR, Fehlings M, et al. Measurement techniques for lower cervical spine injuries: Consensus statement of the Spine Trauma Study Group. Spine. 2006;31:603–609.
37.
Bono CM, Vaccaro AR, Fehlings M, et al. Measurement techniques for upper cervical spine injuries: Consensus statement of the Spine Trauma Study Group. Spine. 2007;32:593–600.
38.
Botelho RV, de Souza Palma AM, Abgussen CM, et al. Traumatic vertical atlantoaxial instability: the risk associated with skull traction. Case report and literature review. Eur Spine J. 2000;9:430–433.
39.
Boullosa JL, Colli BO, Carlotti CG Jr, et al. Surgical management of axis’ traumatic spondylolisthesis (hangman’s fracture). Arq Neuropsiquiatr. 2004;62:821–826.
40.
Boynton LW, Kalb R. Double lumen sign as demonstrated by computerized tomography in spine dislocation. Spine. 1983;8:910–912.
41.
Bransford RJ, Stevens DW, Uyeji S, et al. Halo vest treatment of cervical spine injuries: A success and survivorship analysis. Spine. 2009;34:1561–1566.
42.
Bristol R, Henn JS, Dickman CA. Pars screw fixation of a hangman’s fracture: Technical case report. Neurosurgery. 2005;56:E204; discussion E.
43.
Brodke DS, Anderson PA, Newell DW, et al. Comparison of anterior and posterior approaches in cervical spinal cord injuries. J Spinal Disord Tech. 2003;16:229–235.
44.
Brooks A, Jenkins E. Atlanto-axial arthrodesis by the wedge compression method. J Bone Joint Surg Am. 1978;60:279–284.
45.
Bucholz RD, Cheung KC. Halo vest versus spinal fusion for cervical injury: Evidence from an outcome study. J Neurosurg. 1989;70:884–892.
46.
Burke JP, Gerszten PC, Welch WC. Iatrogenic vertebral artery injury during anterior cervical spine surgery. Spine J. 2005;5:508–514.
47.
Cabanela ME, Ebersold MJ. Anterior plate stabilization for bursting teardrop fractures of the cervical spine. Spine. 1988;13:888–891.
48.
Capuano C, Costagliola C, Shamsaldin M, et al. Occipital condyle fractures: A hidden nosologic entity. An experience with 10 cases. Acta Neurochir (Wien). 2004;146:779–784.
49.
Caroli E, Rocchi G, Orlando ER, et al. Occipital condyle fractures: Report of five cases and literature review. Eur Spine J. 2005;14:487–492.
50.
Carreon LY, Dimar JR. Early versus late stabilization of spine injuries. Spine. 2011;36:E727–E733.
51.
Carroll EA, Gordon B, Sweeney CA, et al. Traumatic atlantoaxial distraction injury: A case report. Spine. 2001;26:454–457.
52.
Chaudhary A, Drew B, Orr RD, et al. Management of type II odontoid fractures in the geriatric population: Outcome of treatment in a rigid cervical orthosis. J Spinal Disord Tech. 2010;23:317–320.
53.
Chen JY, Soares G, Lambiase R, et al. A previously unrecognized connection between occipital condyle fractures and internal carotid artery injuries (carotid and condyles). Emerg Radiol. 2006;12:192–195.
54.
Chen L, Yang H, Yang T, et al. Effectiveness of surgical treatment for traumatic central cord syndrome. J Neurosurg Spine. 2009;10:3–8.
55.
Chen TY, Dickman CA, Eleraky M, et al. The role of decompression for acute incomplete cervical spinal cord injury in cervical spondylosis. Spine. 1998;23:2398–2403.
56.
Chendrasekhar A, Moorman DW, Timberlake GA. An evaluation of the effects of semirigid cervical collars in patients with severe closed head injury. Am Surg. 1998;64:604–606.
57.
Chittiboina P, Wylen E, Ogden A, et al. Traumatic spondylolisthesis of the axis: A biomechanical comparison of clinically relevant anterior and posterior fusion techniques. J Neurosurg Spine. 2009;11:379–387.
58.
Chugh S, Kamian K, Depreitere B, et al. Occipital condyle fracture with associated hypoglossal nerve injury. Can J Neurol Sci. 2006;33:322–324.
59.
Clark CR, White AA III. Fractures of the dens: A multicenter study. J Bone Joint Surg Am. 1985;67:1340–1348.
60.
Clayton JL, Harris MB, Weintraub SL, et al. Risk factors for cervical spine injury [published online ahead of print July 2, 2011]. Injury. 2012;43(4):431–435. doi:10.1016/j.injury.2011.06.022.
61.
Colterjohn NR, Bednar DA. Identifiable risk factors for secondary neurologic deterioration in the cervical spine-injured patient. Spine. 1995;20:2293–2297.
62.
Como JJ, Leukhardt WH, Anderson JS, et al. Computed tomography alone may clear the cervical spine in obtunded blunt trauma patients: A prospective evaluation of a revised protocol. J Trauma. 2011;70:345–351.
63.
Coric D, Wilson JA, Kelly DL Jr. Treatment of traumatic spondylolisthesis of the axis with nonrigid immobilization: a review of 64 cases. J Neurosurg. 1996;85:550–554.
64.
Cotler JM, Herbison GJ, Nasuti JF, et al. Closed reduction of traumatic cervical spine dislocation using traction weights up to 140 pounds. Spine. 1993;18:386–390.
65.
Cusick JF, Pintar FA, Yoganandan N, et al. Wire fixation techniques of the cervical facets. Spine. 1997;22:970–975.
66.
Cusick JF, Yoganandan N, Pintar FA, et al. Biomechanics of cervical spine facetectomy and fixation techniques. Spine. 1988;13:808–812.
67.
Daffner RH. Helical CT of the cervical spine for trauma patients: A time study. AJR Am J Roentgenol. 2001;177:677–679.
68.
Daffner RH, Brown RR, Goldberg AL. A new classification for cervical vertebral injuries: influence of CT. Skeletal Radiol. 2000;29:125–132.
69.
Daniels AH, Riew KD, Yoo JU, et al. Adverse events associated with anterior cervical spine surgery. J Am Acad Orthop Surg. 2008;16:729–738.
70.
DelRossi G, Horodyski M, Heffernan TP, et al. Spine-board transfer techniques and the unstable cervical spine. Spine. 2004;29:E134–E144.
71.
Dimar JR, Glassman SD, Raque GH, et al. The influence of spinal canal narrowing and timing of decompression on neurologic recovery after spinal cord contusion in a rat model. Spine. 1999;24:1623–1633.
72.
DiPaola CP, Conrad BP, Horodyski MB, et al. Cevial spine motion generated with manual versus Jackson table turning methods in a cadaveric C1-C2 global instability model. Spine. 2009;34:2912–2918.
73.
Dmitriev AE, Lehman RA Jr, Helgeson MD, et al. Acute and long-term stability of atlantoaxial fixation methods: A biomechanical comparison of pars, pedicle, and intralaminar fixation in an intact and odontoid fracture model. Spine. 2009;34:365–370.
74.
Doherty BJ, Heggeness MH, Esses SI. A biomechanical study of odontoid fractures and fracture fixation. Spine. 1993;18:178–184.
75.
Dorai Z, Morgan H, Coimbra C. Titanium cage reconstruction after cervical corpectomy. J Neurosurg. 2003;99:3–7.
76.
Duggal N, Chamberlain RH, Perez-Garza LE, et al. Hangman’s fracture: A biomechanical comparison of stabilization techniques. Spine. 2007;32:182–187.
77.
Dvorak MF, Fisher CG, Aarabi B, et al. Clinical outcomes of 90 isolated unilateral facet fractures, subluxations, and dislocations treated surgically and nonoperatively. Spine. 2007;32:3007–3013.
78.
Dvorak MF, Fisher CG, Fehlings MG, et al. The surgical approach to subaxial cervical spine injuries: an evidence-based algorithm based on the SLIC classification system. Spine. 2007;32:2620–2629.
79.
Dvorak MF, Johnson MG, Boyd M, et al. Long-term health-related quality of life outcomes following Jefferson-type burst fractures of the atlas. J Neurosurg Spine. 2005;2:411–417.
80.
Ebraheim NA, Xu R, Knight T, et al. Morphometric evaluation of lower cervical pedicle and its projection. Spine. 1998;22:1–6.
81.
Edeiken-Monroe B, Wagner LK, Harris JH. Hyperextension dislocation of the cervical spine. AJR Am J Roentgenol. 1986;146:803–808.
82.
Einsiedel T, Schmelz A, Arand M, et al. Injuries of the cervical spine in patients with ankylosing spondylitis: Experience at two trauma centers. J Neurosurg Spine. 2006;5:33–45.
83.
Eismont FJ, Arena MJ, Green BA. Extrusion of an intervertebral disc associated with traumatic subluxation or dislocation of cervical facets. Case report. J Bone Joint Surg Am. 1991;73:1555–1560.
84.
ElSaghir H, Bohm H. Anderson type II fracture of the odontoid process: results of anterior screw fixation. J Spinal Disord. 2000;13:527–530; discussion 531.
85.
Ersmark H, Kalen R. A consecutive series of 64 halo-vest-treated cervical spine injuries. Arch Orthop Trauma Surg. 1986;105:243–246.
86.
Farmer J, Vaccaro A, Balderston R, et al. The changing nature of admission to a spinal cord injury center: Violence on the rise. J Spinal Disord. 1998;11:400–403.
87.
Fehlings MG, Arvin B. The timing of surgery in patients with central spinal cord injury. J Neurosurg Spine. 2009;10:1–2.
88.
Fehlings MG, Cooper PR, Errico TJ. Posterior plates in the management of cervical instability: Long-term results in 44 patients. J Neurosurg. 1994;81:341–349.
89.
Fehlings MG, Perrin RG. The timing of surgical intervention in the treatment of spinal cord injury: A systematic review of recent clinical evidence. Spine. 2006;31(suppl 11):S28–S35.
90.
Fehlings MG, Rabin D, Sears W, et al. Current practice in the timing of surgical intervention in spinal cord injury. Spine. 2010;35(suppl 21):S166–S173.
91.
Feiz-Erfan I, Gonzalez LF, Dickman CA. Atlantooccipital transarticular screw fixation for the treatment of traumatic occipitoatlantal dislocation. Technical note. J Neurosurg Spine. 2005;2:381–385.
92.
Feldborg Nielsen C, Annertz M, Persson L, et al. Fusion or stabilization alone for acute distractive flexion injuries in the mid to lower cervical spine. Eur Spine J. 1997;6:197–202.
93.
Fielding JW. Tears of the transverse ligament of the atlas. J Bone Joint Surg Am. 1974;56A:1683–1691.
94.
Fielding JW, Hawkins RJ. Atlano-axial rotatory fixation. J Bone Joint Surg Am. 1977;51A:37.
95.
Fisher CG, Dvorak MF, Leith J, et al. Comparison of outcomes for unstable lower cervical flexion teardrop fractures managed with halo thoracic vest versus anterior corpectomy and plating. Spine. 2002;27:160–166.
96.
Fisher CG, Sun JC, Dvorak M. Recognition and management of atlanto-occipital dislocation: Improving survival from an often fatal condition. Can J Surg. 2001;44:412–420.
97.
Freeman BJ, Behensky H. Bilateral occipital condyle fractures leading to retropharyngeal haematoma and acute respiratory distress. Injury. 2005;36:207–212.
98.
Friedman D, Flanders A, Thomas C, et al. Vertebral artery injury after acute cervical spine trauma: rate of occurrence as detected by MR angiography and assessment of clinical consequences. AJR Am J Roentgenol. 1995;164:443–447.
99.
Fuentes S, Bouillot P, Palombi O, et al. Traumatic atlantoaxial rotatory dislocation with odontoid fracture: Case report and review. Spine. 2001;26:830–834.
100.
Gallie W. Fractures and dislocations of the cervical spine. Am J Surg. 1939;46:495–499.
101.
Garrett M, Consiglieri G, Kakarla UK, et al. Occipitoatlantal dislocation. Neurosurgery. 2010;66:A48–A55.
102.
Garvey TA, Eismont FJ, Roberti LJ. Anterior decompression, structural bone grafting, and Caspar plate stabilization for unstable cervical spine fractures and/or dislocations. Spine. 1992;17:S431–S435.
103.
Goffin J, van Loon J, Van Calenbergh F, et al. Long-term results after anterior cervical fusion and osteosynthetic stabilization for fractures and/or dislocations of the cervical spine. J Spinal Disord. 1995;8:500–508.
104.
Goldberg W, Mueller C, Panacek E, et al. Distribution and patterns of blunt traumatic cervical spine injury. Ann Emerg Med. 2001;38:17–21.
105.
Goldstein SJ, Woodring JH, Young AB. Occipital condyle fracture associated with cervical spine injury. Surg Neurol. 1982;17:350–352.
106.
Govender S, Vlok GJ, Fisher-Jeffes N, et al. Traumatic dislocation of the atlanto-occipital joint. J Bone Joint Surg Br. 2003;85:875–878.
107.
Graham B, Van Peteghem PK. Fractures of the spine in ankylosing spondylitis. Diagnosis, treatment, and complications. Spine. 1989;14:803–807.
108.
Grant GA, Mirza SK, Chapman JR, et al. Risk of early closed reduction in cervical spine subluxation injuries. J Neurosurg. 1999;90:13–18.
109.
Grauer JN, Shaft B, Hilibrand AS, et al. Proposal of a modified, treatment-oriented classification of odontoid fractures. Spine J. 2005;5:123–129.
110.
Graziano G, Jaggers C, Lee M, et al. A comparative study of fixation techniques for type II fractures of the odontoid process. Spine. 1993;18:2383–2387.
111.
Greene KA, Dickman CA, Marciano FF, et al. Acute axis fractures. Analysis of management and outcome in 340 consecutive cases. Spine. 1997;22:1843–1852.
112.
Grubb RL, Currier BL, Shih JS, et al. Biomechanical evaluation of anterior cervical spine stabilization. Spine. 1998;23:886–892.
113.
Guest J, Eleraky MA, Apostolides PJ, et al. Traumatic central cord syndrome: Results of surgical management. J Neurosurg. 2002;97(suppl 1):25–32.
114.
Haher TR, Yeung AW, Caruso SA, et al. Occipital screw pullout strength. A biomechanical investigation of occipital morphology. Spine. 1999;24:5–9.
115.
Hanson JA, Deliganis AV, Baxter AB, et al. Radiologic and clinical spectrum of occipital condyle fractures: Retrospective review of 107 consecutive fractures in 95 patients. AJR Am J Roentgenol. 2002;178:1261–1268.
116.
Harms J, Melcher RP. Posterior C1-C2 fusion with polyaxial screw and rod fixation. Spine. 2001;26:2467–2471.
117.
Harrington RM, Budorick T, Hoyt J, et al. Biomechanics of indirect reduction of bone retropulsed into the spinal canal in vertebral fracture. Spine. 1993;18:692–699.
118.
Harris MB, Reichmann WM, Bono CM, et al. Mortality in elderly patients after cervical spine fractures. J Bone Joint Surg Am. 2010;92:567–574.
119.
Harris MB, Schoenfeld AJ. Spinal cord injury: Pathophysiology and current treatment strategies. In: Schmidt A, Teague DC, eds. Orthopaedic Knowledge Update: Trauma. 4th ed. Rosemont, IL: American Academy of Orthopaedic Surgeons; 2010:337–345.
120.
Harris MB, Sethi RK. The initial assessment and management of the multiple-trauma patient with an associated spine injury. Spine. 2006;31(suppl 11): S9–S15.
121.
Harris TJ, Blackmore CC, Mirza SK, et al. Clearing the cervical spine in obtunded patients. Spine. 2008;33:1547–1553.
122.
Harrop JS, Sharan AD, Vaccaro AR, et al. The cause of neurologic deterioration after acute cervical spinal cord injury. Spine. 2001;26:340–346.
123.
Hart R, Saterbak A, Rapp T, et al. Nonoperative management of dens fracture nonunion in elderly patients without myelopathy. Spine. 2000;25:1339–1343.
124.
Heary RF, Hunt CD, Krieger AJ, et al. Acute stabilization of the cervical spine by halo/vest application facilitates evaluation and treatment of multiple trauma patients. J Trauma. 1992;33:445–451.
125.
Hein C, Richter HP, Rath SA. Atlantoaxial screw fixation for the treatment of isolated and combined unstable Jefferson fractures—experiences with 8 patients. Acta Neurochir (Wien). 2002;144:1187–1192.
126.
Herr CH, Ball PA, Sargent SK, et al. Sensitivity of prevertebral soft tissue measurement of C3 for detection of cervical spine fractures and dislocations. Am J Emerg Med. 1998;16:346–349.
127.
Horn EM, Feiz-Erfan I, Lekovic GP, et al. Survivors of occipitoatlantal dislocation injuries: Imaging and clinical correlates. J Neurosurg Spine. 2007;6:113–120.
128.
Hsu WK, Anderson PA. Odontoid fractures: Update on management. J Am Acad Orthop Surg. 2010;18:383–394.
129.
Ito Y, Sugimotot Y, Tomioka M, et al. Does high does methylprednisolone sodium succinate really improve neurological status in patient with acute cervical cord injury: A prospective study about neurological recovery and early complications. Spine. 2009;34:2121–2124.
130.
Jain VK, Mittal P, Banerji D, et al. Posterior occipitoaxial fusion for atlantoaxial dislocation associated with occipitalized atlas. J Neurosurg. 1996;84:559–564.
131.
Jea A, Tatsui C, Farhat H, et al. Vertically unstable type III odontoid fractures: Case report. Neurosurgery. 2006;58:E797.
132.
Jeanneret B, Magerl F. Primary posterior fusion C1/2 in odontoid fractures: indications, technique, and results of transarticular screw fixation. J Spinal Disord. 1992;5:464–475.
133.
Jeanneret B, Magerl F, Ward JC. Overdistraction: a hazard of skull traction in the management of acute injuries of the cervical spine. Arch Orthop Trauma Surg. 1991;110:242–245.
134.
Johnson JL, Cannon D. Nonoperative treatment of the acute tear-drop fracture of the cervical spine. Clin Orthop. 1982;168:108–112.
135.
Johnson M, Dvorak MF, Fisher C. The radiographic failure of single-segment anterior cervical plate fixation in traumatic cervical flexion/distraction injuries. Spine J. 2002;5S:57S.
136.
Johnson RM, Owen JR, Hart DL, et al. Cervical orthoses: A guide to their selection and use. Clin Orthop. 1981;154:34–35.
137.
Jovanovich MS. A comparative study of the foramen transversarium of the sixth and seventh vertebra. Surg Radiol Anat. 1990;12:167–172.
138.
Kang JD, Figgie MP, Bohlman HH. Sagittal measurements of the cervical spine in subaxial fractures and dislocations. An analysis of two hundred and eighty-eight patient with and without neurological deficits. J Bone Joint Surg Am. 1994;76:1617–1628.
139.
Katonis P, Papadakis SA, Galanakos S, et al. Lateral mass screw complications: Analysis of 1662 screws. J Spinal Disord Tech. 2011;24:415–420.
140.
Kilburg C, Sullivan HG, Mathiason MA. Effect of approach side during anterior cervical discectomy and fusion on the incidence of recurrent laryngeal nerve injury. J Neurosurg Spine. 2006;4:273–277.
141.
Koech F, Ackland HM, Carma DK, et al. Nonoperative management of type II odontoid fractures in the elderly. Spine. 2008;33:2881–2886.
142.
Koivikko MP, Kiuru MJ, Koskinen SK, et al. Factors associated with nonunion in conservatively-treated type-II fractures of the odontoid process. J Bone Joint Surg Br. 2004;86(8):1146–1151.
143.
Kupcha P, An H, Cotler J. Gunshot wounds to the cervical spine. Spine. 1990;15:1058–1063.
144.
Kwon BK, Fisher CG, Boyd MC, et al. A prospective randomized controlled trial of anterior compared with posterior stabilization for unilateral facet injuries of the cervical spine. J Neurosurg Spine. 2007;7:1–12.
145.
Kwon BK, Vaccaro AR, Grauer JN, et al. Subaxial cervical spine trauma. J Am Acad Orthop Surg. 2006;14:78–89.
146.
La Rosa G, Conti A, Cardali S, et al. Does early decompression improve neurological outcome of spinal cord injured patients? Appraisal of the literature using a meta-analytical approach. Spinal Cord. 2004;42:503–512.
147.
Lador R, Ben-Galim PJ, Weiner BK, et al. The association of occipitocervical dissociation and death as a result of blunt trauma. Spine J. 2010;10:1128–1132.
148.
Lapsiwala SB, Anderson PA, Oza A, et al. Biomechanical comparison of four C1 to C2 rigid fixative techniques: Anterior transarticular, posterior transarticular, C1 to C2 pedicle, and C1 to C2 intralaminar screws. Neurosurgery. 2006;58:516–521; discussion 521.
149.
Lee AS, Wainwright AM, Newton DA. Rogers’ posterior cervical fusion: A 3-month radiological review. Injury. 1996;27:169–173.
150.
Lee TT, Green BA, Petrin DR. Treatment of stable burst fracture of the atlas (Jefferson fracture) with rigid cervical collar. Spine. 1998;23:1963–1967.
151.
Lerman JA, Haynes RJ, Koeneman EJ, et al. A biomechanical comparison of Gardner-Wells tongs and halo device used for cervical spine traction. Spine. 1994;19:2403–2406.
152.
Levi AD, Hurlbert RJ, Anderson P, et al. Neurologic deterioration secondary to unrecognized spinal instability following trauma: A multicenter study. Spine. 2006;31:451–458.
153.
Levine AM, Edwards CC. The management of traumatic spondylolisthesis of the axis. J Bone Joint Surg Am. 1985;67:217–226.
154.
Li XF, Dai LY, Lu H, et al. A systematic review of the management of hangman’s fractures. Eur Spine J. 2006;15:257–269.
155.
Lifeso RM, Colucci MA. Anterior fusion for rotationally unstable spine fractures. Spine. 2000;25:2028–2034.
156.
Lifshutz J, Colohan A. A brief history of therapy for traumatic spinal cord injury. Neurosurg Focus. 2004;16:Article 5.
157.
Ljunggren B, al Refai M, Sharma S, et al. Functional recovery after near complete traumatic deficit of the cervical cord lasting more than 24 h. Br J Neurosurg. 1992;6:375–380.
158.
Ludwig SC, Vaccaro AR, Balderston RA, et al. Immediate quadriparesis after manipulation for bilateral cervical facet subluxation. A case report. J Bone Joint Surg Am. 1997;79A:587–590.
159.
Lukhele M. Atlanto-axial rotatory fixation. S Afr Med J. 1996;86:1549–1552.
160.
Maak TG, Grauer JN. The contemporary treatment of odontoid injuries. Spine. 2006;31:S53–S60.
161.
Majercik S, Tashjian RZ, Biffl WL, et al. Halo vest immobilization in the elderly: A death sentence? J Trauma. 2005;59:350–357.
162.
Martinez-Lage JF, Perez-Espejo MA, Masegosa J, et al. Bilateral brain abscesses complicating the use of Crutchfield tongs. Childs Nerv Syst. 1986;2:208–210.
163.
Matar LD, Doyle AJ. Prevertebral soft-tissue measurements in cervical spine injury. Australas Radiol. 1997;41:229–237.
164.
McBride AD, Mukherjee DP, Kruse RN, et al. Anterior screw fixation of type II odontoid fractures. A biomechanical study. Spine. 1995;20:1855–1859; discussion 1859–1860.
165.
McCulloch PT, France J, Jones DL, et al. Helical computed tomography alone compared with plain radiographs with adjunct computed tomography to evaluate the cervical spine after high-energy trauma. J Bone Joint Surg Am. 2005;87:2388–2394.
166.
Menaker J, Stein DM, Philip AS, et al. 40-slice multidetector CT: Is MRI still necessary for cervical spine clearance after blunt trauma. Am Surg. 2010;76:157–163.
167.
Meyer PG, Hartman JT, Leo JS. Sentinel spinous process fractures. Surg Neurol. 1982;18:174–178.
168.
Mihara H, Cheng BC, David SM, et al. Biomechanical comparison of posterior cervical fixation. Spine. 2001;26:1662–1667.
169.
Miller CP, Brubacher JW, Biswas D, et al. The incidence of noncontiguous spinal fractures and other traumatic injuries associated with cervical spine fractures: A 10-year experience at an academic medical center. Spine. 2011;36:1532–1540.
170.
Miyachi S, Okamura K, Wantanabe M, et al. Cerebellar stroke due to vertebral artery occlusion after cervical spine trauma. Two case reports. Spine. 1994;19:83–88.
171.
Miyazaki C, Katsume M, Yamazaki T, et al. Unusual occipital condyle fracture with multiple nerve palsies and Wallenberg syndrome. Clin Neurol Neurosurg. 2000;102:255–258.
172.
Muchow RD, Resnick DK, Abdel MP, et al. Magnetic resonance imaging (MRI) in the clearance of the cervical spine in blunt trauma: A meta-analysis. J Trauma. 2008;64:179–189.
173.
Mulder DS, Wallace DH, Woolhouse FM. The use of fiberoptic bronchoscope to facilitate endotracheal intubation following head and neck trauma. J Trauma. 1975;15:638–640.
174.
Muller EJ, Schwinnen I, Fischer K, et al. Non-rigid immobilisation of odontoid fractures. Eur Spine J. 2003;12:522–525.
175.
Muratsu H, Doita M, Yanagi T, et al. Cerebellar infarction resulting from vertebral artery occlusion associated with a Jefferson fracture. J Spinal Disord Tech. 2005;18:293–296.
176.
Nazarian SM, Louis RP. Posterior internal fixation with screw plates in traumatic lesions of the cervical spine. Spine. 1991;16:S64–S71.
177.
Niijima K. Hangman’s fracture vs. hanged-man’s fracture. J Neurosurg. 1991;75:669.
178.
Nimityongskul P, Bose WJ, Hurely DP, et al. Superficial temporal artery laceration. A complication of skull tong traction. Orthop Rev. 1992;21:761, 764–765.
179.
Northrup BE, Vaccaro AR, Rosen JE, et al. Occurrence of infection in anterior cervical fusion for spinal cord injury after tracheostomy. Spine. 1995;20:2449–2453.
180.
Nowak DD, Lee JK, Gelb DE, et al. Central cord syndrome. J Am Acad Orthop Surg. 2009;17:756–765.
181.
Nucci RC, Seigal S, Merola AA, et al. Computed tomographic evaluation of the normal adult odontoid. Implications for internal fixation. Spine. 1995;20:264–270.
182.
Oda I, Abumi K, Sell LC, et al. Biomechanical evaluation of five different occipitoatlanto-axial fixation techniques. Spine. 1999;24:2377–2382.
183.
Orlando ER, Caroli E, Ferrante L. Management of the cervical esophagus and hypofarinx perforations complicating anterior cervical spine surgery. Spine. 2003;28:E290–E295.
184.
Panjabi MM, Shin EK, Chen NC, et al. Internal morphology of human cervical pedicles. Spine. 2000;25:1197–1205.
185.
Panjabi MM, White AA, Johnson RM. Cervical spine mechanics as a function of transection of components. J Biomech. 1975;8:327–336.
186.
Papadopoulos SM, Selden NR, Quint DJ, et al. Immediate spinal cord decompression for cervical spinal cord injury: Feasibility and outcome. J Trauma. 2002;52:323–332.
187.
Papagelopoulos PJ, Currier BL, Neale PG, et al. Biomechanical evaluation of posterior screw fixation in cadaveric cervical spines. Clin Orthop. 2003;411:13–24.
188.
Parbhoo AH, Govender S, Corr P. Vertebral artery injury in cervical spine trauma. Injury. 2001;32:565–568.
189.
Patel AA, Lindsey R, Bessey JT, et al. Surgical treatment of unstable type II odontoid fractures in skeletally mature individuals. Spine. 2010;35(suppl 21S):S209–S218.
190.
Pull ter Gunne AF, Aquarius AE, Roukema JA. Risk factors predicting mortality after blunt traumatic cervical fracture. Injury. 2008;39:1437–1441.
191.
Rabinowitz RS, Eck JC, Harper CM Jr, et al. Urgent surgical decompression compared to methylprednisolone for the treatment of acute spinal cord injury: A randomized prospective study in beagle dogs. Spine. 2008;33:2260–2268.
192.
Ramasamy A, Midwinter M, Mahoney P, et al. Learning the lessons from conflict: Pre-hospital cervical spine stabilisation following ballistic neck trauma. Injury. 2009;40:1342–1345.
193.
Randle MJ, Wolf A, Levi L, et al. The use of anterior Caspar plate fixation in acute cervical spine injury. Surg Neurol. 1991;36:181–189.
194.
Razack N, Green B, Levi AD. The management of traumatic cervical bilateral facet fracture-dislocations with unicortical anterior plates. J Spinal Disord. 2000;13:374–381.
195.
Reindl R, Sen M, Aebi M. Anterior instrumentation for traumatic C1-C2 instability. Spine. 2003;28:E329–E333.
196.
Richter D, Latta LL, Milne EL, et al. The stabilizing effects of different orthoses in the intact and unstable upper cervical spine: A cadaver study. J Trauma. 2001;50:848–854.
197.
Rogers WA. Fracture and dislocations of the cervical spine: An end result study. J Bone Joint Surg Am. 1957;39:341–376.
198.
Rojas CA, Bertozzi JC, Martinez CR, et al. Reassessment of the craniocervical junction: normal values on CT. AJNR Am J Neuroradiol. 2007;28:1819–1823.
199.
Roy-Camille R, Saillant G, Laville C, et al. Treatment of lower cervical spinal injuries: C3 to C7. Spine. 1992;17:S442–S446.
200.
Ruf M, Melcher R, Harms J. Transoral reduction and osteosynthesis C1 as a function-preserving option in the treatment of unstable Jefferson fractures. Spine. 2004;29:823–827.
201.
Rushton SA, Vaccaro AR, Levine MJ, et al. Bivector traction for unstable cervical spine fractures: a description of its application and preliminary results. J Spinal Disord. 1997;10:436–440.
202.
Sack JA, Etame AB, Shah GV, et al. Management and outcomes of patients undergoing surgery for traumatic cervical fracture-subluxation associated with asymptomatic vertebral artery injury. J Spinal Disord Tech. 2009;22:86–90.
203.
Saifuddin A, Green R, White J. Magnetic resonance imaging of the cervical ligaments in the absence of trauma. Spine. 2003;28:1686–1691.
204.
Sasso RC, Ruggiero RA Jr, Reilly TM, et al. Early reconstruction failures after multilevel cervical corpectomy. Spine. 2003;28:140–142.
205.
Sawers A, DiPaola CP, Rechtine GR II. Suitability of the noninvasive halo for cervical spine injuries: A retrospective analysis of outcomes. Spine J. 2009;9:216–220.
206.
Scher AT. Overdistraction of cervical spinal injuries. S Afr Med J. 1981;59:639–641.
207.
Schneider AM, Hipp JA, Nguyen L, et al. Reduction in head and intervertebral motion provided by 7 contemporary cervical orthoses in 45 individuals. Spine. 2007;32:E1–E6.
208.
Schoenfeld AJ. Orthopaedic surgery in the United States Army: A historical review. Mil Med. 2011;176:689–695.
209.
Schoenfeld AJ, Bono CM. Measuring spine fracture outcomes: Common scales and checklists. Injury. 2011;42:265–270.
210.
Schoenfeld AJ, Bono CM, McGuire KJ, et al. Computed tomography alone versus computed tomography and magnetic resonance imaging in the identification of occult injuries to the cervical spine: A meta-analysis. J Trauma. 2010;68:109–114.
211.
Schoenfeld AJ, Bono CM, Reichmann WM, et al. Type II odontoid fractures of the cervical spine: Do treatment type and medical comorbidities affect mortality in elderly patients. Spine. 2011;36:879–885.
212.
Schoenfeld AJ, Harris MB, McGuire KJ, et al. Mortality in elderly patients with hyperostotic disease of the cervical spine after fracture: An age- and sex-matched study. Spine J. 2011;11:257–264.
213.
Schoenfeld AJ, McCriskin B, Hsiao M, et al. Incidence and epidemiology of spinal cord injury within a closed American population: The United States military (2000–2009). Spinal Cord. 2011;49:874–879.
214.
Schoenfeld AJ, Sielski B, Rivera KP, et al. Epidemiology of cervical spine fractures in the US military [published online ahead of print March 9, 2011]. Spine J. 2012;12(9):777–783. doi:10.1016/j.spinee.2011.01.029.
215.
Sears W, Fazl M. Prediction of stability of cervical spine fracture managed in the halo vest and indications for surgical intervention. J Neurosurg. 1990;72:426–432.
216.
Sekhon LH. Posterior cervical lateral mass screw fixation: Analysis of 1026 consecutive screws in 143 patients. J Spinal Disord Tech. 2005;18:297–303.
217.
Seybold EA, Bayley JC. Functional outcome of surgically and conservatively managed dens fractures. Spine. 1998;23:1837–1845.
218.
Shapiro SA. Management of unilateral locked facet of the cervical spine. Neurosurgery. 1993;33:832–837.
219.
Sharpe KP, Rao S, Ziogas A. Evaluation of the effectiveness of the Minerva cervicothoracic orthosis. Spine. 1995;20:1475–1479.
220.
Simon JB, Schoenfeld AJ, Katz JN, et al. Are “normal” multidetector computed tomographic scans sufficient to allow collar removal in the trauma patient? J Trauma. 2010;68:103–108.
221.
Smith CE, Fallon WF. Sevoflurane mask anesthesia for urgent tracheostomy in an uncooperative trauma patient with a difficult airway. Can J Anaesth. 2000;47:242–245.
222.
Spence KF, Decker S, Sell KW. Bursting atlantal fracture associated with rupture of the transverse ligament. J Bone Joint Surg Am. 1970;52:543–549.
223.
Starr JK, Eismont FJ. Atypical hangman’s fractures. Spine. 1993;18:1954–1957.
224.
Stiell IG, Clement CM, Grimshaw J, et al. Implementation of the Canadian C-spine rule: Prospective 12 centre cluster randomised trial. BMJ. 2009;339:b4146.
225.
Stiell IG, Clement CM, McKnight RD, et al. The Canadian C-spine rule versus the NEXUS low-risk criteria in patients with trauma. N Engl J Med. 2003;349:2510–2518.
226.
Subach BR, Morone MA, Haid RW Jr, et al. Management of acute odontoid fractures with single-screw anterior fixation. Neurosurgery. 1999;45:812–819; discussion 819–820.
227.
Swenson TM, Lauerman WC, Blanc RO, et al. Cervical alignment in the immobilized football player: radiographic analysis before and after helmet removal. Am J Sports Med. 1997;25:226–230.
228.
Taggard DA, Traynelis VC. Management of cervical spinal fractures in ankylosing spondylitis with posterior fixation. Spine. 2000;25:2035–2039.
229.
Taller S, Suchomel P, Lukas R, et al. CT-guided internal fixation of a hangman’s fracture. Eur Spine J. 2000;9:393–397.
230.
Tashjian RZ, Majercik S, Biffl WL, et al. Halo-vest immobilization increased early morbidity and mortality in elderly odontoid fractures. J Trauma. 2006;60:199–203.
231.
Templeton PA, Young JW, Mirvis S, et al. The value of retropharyngeal soft tissue measurements in trauma of the adult cervical spine. Cervical spine soft tissue measurements. Skeletal Radiol. 1987;16:98–104.
232.
Teo EC, Paul JP, Evans JH, et al. Experimental investigation of failure load and fracture patterns of C2 (axis). J Biomech. 2001;34:1005–1010.
233.
Torg JS, Sennett B, Vegso JJ, et al. Axial loading injuries to the middle cervical spine segment. An analysis and classification of twenty-five cases. Am J Sports Med. 1991;19:6–20.
234.
Traynelis VC, Marano GD, Dunker RO, et al. Traumatic atlanto-occipital dislocation. Case report. J Neurosurg. 1986;65:863–870.
235.
Tuite GF, Papadopoulos SM, Sonntag VK. Caspar plate fixation for the treatment of complex hangman’s fractures. Neurosurgery. 1992;30:761–764; discussion 764–765.
236.
Tuli S, Tator CH, Fehlings MG, et al. Occipital condyle fractures. Neurosurgery. 1997;41:368–376; discussion 376–377.
237.
Urculo E, Arrazola M, Arrazola M Jr, et al. Delayed glossopharyngeal and vagus nerve paralysis following occipital condyle fracture. Case report. J Neurosurg. 1996;84:522–525.
238.
Vaccaro AR, Daugherty RJ, Sheehan TP, et al. Neurologic outcome of early versus late surgery for cervical spinal cord injury. Spine. 1997;22:2609–2613.
239.
Vaccaro AR, Falatyn SP, Flanders AE, et al. Magnetic resonance evaluation of the intervertebral disc, spinal ligaments, and spinal cord before and after closed traction reduction of cervical spine dislocations. Spine. 1999;24:1210–1217.
240.
Vaccaro AR, Falatyn SP, Scuderi GJ, et al. Early failure of long segment anterior cervical plate fixation. J Spinal Disord. 1998;11:410–415.
241.
Vaccaro AR, Hulbert RJ, Patel AA, et al. The subaxial cervical spine injury classification system: a novel approach to recognize the importance of morphology, neurology, and integrity of the disco-ligamentous complex. Spine. 2007;32:2365–2374.
242.
Vaccaro AR, Lehman AP, Ahlgren BD, et al. Anterior C1-C2 screw fixation and bony fusion through an anterior retropharyngeal approach. Orthopedics. 1999;22:1165–1170.
243.
Vaccaro AR, Madigan L, Bauerle WB, et al. Early halo immobilization of displaced traumatic spondylolisthesis of the axis. Spine. 2002;27:2229–2233.
244.
Vale FL, Burns J, Jackson AB, et al. Combined medical and surgical treatment after acute spinal cord injury: Results of a prospective pilot study to assess the merits of aggressive medical resuscitation and blood pressure management. J Neurosurg. 1997;87:239–246.
245.
van Middendorp JJ, Sloof WBM, Nellestein WR, et al. Incidence of and risk factors for complications associated with halo-vest immobilization: A prospective, descriptive cohort study of 239 patients. J Bone Joint Surg Am. 2009;91:71–79.
246.
Vanderhave KL, Chiravuri S, Caird MS, et al. Cervical spine trauma in children and adults: Perioperative considerations. J Am Acad Orthop Surg. 2011;19:319–327.
247.
Vanderlan WB, Tew BE, Seguin CY, et al. Neurologic sequelae of penetrating cervical trauma. Spine. 2009;34:2646–2653.
248.
Verheggen R, Jansen J. Fractures of the odontoid process: Analysis of the functional results after surgery. Eur Spine J. 1994;3:146–150.
249.
Verheggen R, Jansen J. Hangman’s fracture: Arguments in favor of surgical therapy for type II and III according to Edwards and Levine. Surg Neurol. 1998;49:253–261; discussion 261–262.
250.
Vertullo CJ, Duke PF, Askin GN. Pin-site complications of the halo thoracic brace with routine tightening. Spine. 1997;22:2514–2516.
251.
Vieweg U, Meyer B, Schramm J. Differential treatment in acute upper cervical spine injuries: a critical review of a single-institution series. Surg Neurol. 2000;54:203–210.
252.
Vital JM, Gille O, Senegas J, et al. Reduction technique for uni-and biarticular dislocations of the lower cervical spine. Spine. 1998;23:949–954.
253.
Waters R, Adkins R, Yakura J, et al. Effect of surgery on motor recovery following traumatic spinal cord injury. Spinal Cord. 1996;34:188–192.
254.
Weiner BK, Brower RS. Traumatic vertical atlantoaxial instability in a case of atlantooccipital coalition. Spine. 1997;22:1033–1035.
255.
Wetzel FT, La Rocca H. Grisel’s syndrome: a review. Clin Orthop Relat Res. 1989;240:141.
256.
Whang PG, Goldberg G, Lawrence JP, et al. The management of spinal injuries in patients with ankylosing spondylitis or diffuse idiopathic skeletal hyperostosis: A comparison of treatment methods and clinical outcomes. J Spinal Disord Tech. 2009;22(2):77–85. doi:10.1097/BSD.0b013e3181679bcb.
257.
White A, Panjabi M. Clinical Biomechanics of the Spine. 2nd ed. Philadelphia, PA: Lippincott-Raven; 1990.
258.
White AP, Hashimoto R, Norvell DC, et al. Morbidity and mortality related to odontoid fracture surgery in the elderly population. Spine. 2010;35(suppl 9S):S146–S157.
259.
Whitehill R, Richman JA, Glaser JA. Failure of immobilization of the cervical spine by the halo vest. A report of five cases. J Bone Joint Surg Am. 1986;68A:326–432.
260.
Willis BK, Greiner F, Orrison WW, et al. The incidence of vertebral artery injury after midcervical spine fracture or subluxation. Neurosurgery. 1994;34:441–442.
261.
Woodworth RS, Molinari WJ III, Brandenstein D, et al. Anterior cervical discectomy and fusion with structural allograft and plates for the treatment of unstable posterior cervical injuries. J Neurosurg Spine. 2009;10:93–101.
262.
Ying Z, Wen Y, Xinwei W, et al. Anterior cervical discectomy and fusion for unstable traumatic spondylolisthesis of the axis. Spine. 2008;33:255–258.
263.
Young JP, Young PH, Ackermann MJ, et al. The ponticulus posticus: Implications for screw insertion into the first cervical lateral mass. J Bone Joint Surg Am. 2005;87:2495–2498.
264.
Zipnick RI, Merola AA, Gorup J, et al. Occipital morphology. An anatomic guide to internal fixation. Spine. 1996;21:1719–1724.