Epidemiology of Cervical Injuries
General Principles of Management
Mechanisms of Injury
History and Physical Examination
Imaging and Other Diagnostic Studies
Outcome Scores and Instruments
Pathoanatomy and Applied Anatomy
Upper Cervical Spine (Occiput to C2)
Lower Cervical Spine (C3–C7)
Spinal Canal and Canal Compromise
Cervical Spinal Cord Anatomy
Skull-Based Traction and Closed Reduction
Posterior Approaches to the Cervical Spine
Posterior Instrumentation and Fusion of the Cervical Spine
Authors’ Preferred Method of Treatment
Posterior Stabilization and Fusion of the Upper Cervical Spine
Posterior Stabilization and Fusion of the Lower Cervical Spine
Stabilization of the Lower Cervical Spine
Complications of Surgery
Complications Associated with the Anterior Approach
Complications Associated with the Posterior Approach
Perioperative Neurologic Deficit
Early Postoperative Complications
Late Postoperative Complications
Treatment Options for Specific Injuries
Occipitocervical Dislocation (C0–C1)
Pearls and Pitfalls
Occipital Condyle Fractures
Diagnosis and Classification
Atlas Fractures (C1)
Isolated C1 Ring Fractures
Sagittal Atlantoaxial Instability without Fracture (C1–C2)
Sagittal Atlantoaxial Instability
Atlantoaxial Rotatory Dislocation (C1–C2)
Odontoid Fractures (C2)
Traction and Reduction
Halo Vest Immobilization
Anterior Odontoid Screw
Posterior C1–C2 Fusion
Anterior C1–C2 Fusion
Posterior C1–C2 Stabilization and Fusion with C1 Lateral Mass C2 Isthmus Screws
Hangman’s Fractures (Traumatic Spondylolisthesis, C2–C3)
Anterior Discectomy and Fusion
Subaxial Cervical Fractures and Dislocations (C3–C7)
Subaxial Cervical Injury Scoring Systems
Vertebral Body Fractures
Pedicle and Lamina Fractures
Anterior Tension Band Disruption
Mechanism of Injury
Treatment of Specific Injuries
Anterior Corpectomy and Stabilization
Posterior Instrumentation and Fusion
Flexion-Type Teardrop Fractures
Facet Fractures without Dislocation
Anterior Tension Band Injuries
Cervical Injuries of the Ankylosed and Spondylotic Spine
Spinal Cord Injury Without Instability in the Spondylotic Spine
Gunshot Wounds to the Cervical Spine
Vertebral Artery Injury in Association with Cervical Trauma
C7 Spinous Process (Clay-Shoveler’s Fractures)
Controversies and Future Directions
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.
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
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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.
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).
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.
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 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.
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.
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.
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.
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).
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 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).
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.
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.
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.
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
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.
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.
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 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.
Surgical stabilization has a role in select cases, often after the failure of nonoperative measures, or concomitant disruption of the transverse ligament.
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
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.
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.
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.
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.
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 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.
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.
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
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
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 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.
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
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
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.
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.
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
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.
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.
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.
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
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.
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.
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 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.
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
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 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.
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 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.
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
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.
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.
Surgical results for odontoid fractures vary according to technique. The results of individual operative methods are discussed below.
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.
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 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
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.
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.
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.
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
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
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).
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.
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.
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.
A standard posterior midline approach to expose the posterior elements of C1 and C2 is performed, as described earlier.
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.
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.
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.
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.
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
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).
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
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.
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.
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 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.
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.
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.
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.
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.
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.
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.
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.
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.
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).
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).
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.
DE injuries, like DF injuries, are associated with substantial ligamentous injury. Initial failure occurs through the anterior ligaments (Fig. 44-50).
LF injuries occur through compression on one side of the spine. With further energy, the contralateral side can fail under tension.
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
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.
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.
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%.
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.
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 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.
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.
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.
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.
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
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
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.
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.
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.
As yet, there are no series reporting the results of nonoperative management for simple compression fractures of the subaxial cervical spine.
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.
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.
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.
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.
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.
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.
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.
PLC, posterior ligamentous complex.
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.
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.
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.
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.
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
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.
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.
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.
GW, gardner wells; PLC, posterior ligamentous complex.
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
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.
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
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.
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).
MRI, magnetic resonance imaging.
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.
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.
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.
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 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.
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.
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 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.
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.
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.
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.
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.
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).
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 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.
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 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.
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.
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
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.
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.