Chapter 56: Knee Dislocations

Daniel B. Whelan, Bruce A. Levy

Chapter Outline

Introduction to Knee Dislocations

Frank dislocation of the tibiofemoral articulation at the knee is a devastating injury with the potential for limb-threatening complications (Fig. 56-1). Traditionally, it was considered a rare injury but—with improved diagnostic suspicion and accuracy—it has been noted with increased frequency.24,83,97,168 Complicating estimates of the true incidence is the fact that a knee that was dislocated or subluxed at the time of trauma will very often spontaneously reduce prior to assessment.208 
Figure 56-1
Anteroposterior (AP) radiograph of a severe knee dislocation.
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Prognosis following a knee dislocation is often determined by the type and severity of associated injury. Traction to surrounding nerves and blood vessels at the time of joint separation can compromise the viability of the involved limb acutely or dramatically impair function in the long term. The high energy of trauma required to cause a dislocation of such a large joint usually brings with it systemic injuries that can be life threatening. Not uncommonly, patients who have sustained knee dislocations also have concomitant trauma to the head, chest, and abdomen.214 
The first publication on knee dislocations dates to 1825. Sir Astley Cooper suggested: “Of this I have only seen one instance, and I conclude it, therefore, to be a rare occurrence…there are scarcely any accidents to which the body is liable which more demand immediate amputation than these.”26 In 1850, Birkett13 described the first attempted reduction of an open dislocation under chloroform anesthesia. With the introduction of radiographs at the turn of the century, more accurate descriptions and diagnosis became possible. In the modern era (1950–1990), the majority of the literature pertaining to knee dislocations has been case series of varying sizes describing primarily open repair techniques for torn or stretched ligaments. More recently, the introduction of arthroscopy and the use of modern reconstructive techniques have advanced care considerably. The concentration of expertise and resources in specialized trauma centers has allowed for the acquisition of experience through multiple cases with what was once thought to be an injury few surgeons would see more than once in a lifetime of practice. Effective treatment strategies have evolved from a fusion of principles derived from the fields of orthopedic sports medicine (applied anatomy, biomechanics, and knee function) and traumatology (polytrauma algorithms, fracture care, and high-energy soft tissue trauma). 

Assessment of Knee Dislocations

Mechanisms of Injury for Knee Dislocations

The potential mechanisms by which the knee can become dislocated and/or subluxed are varied. A common element is that of hyperextension, which is thought to lead to cruciate ligament disruption, with combined varus, valgus, or rotatory forces that result in the various patterns of collateral ligament injury97,176 (Fig. 56-2). 
Figure 56-2
Combined hyperextension and varus mechanism of injury resulting in knee dislocation
 
(From Levy BA, Stuart MJ, Whelan DB. Posterolateral instability of the knee: evaluation, treatment, results. Sports Med Arthrosc Rev. 2010;18(4):254–262, with permission).
(From Levy BA, Stuart MJ, Whelan DB. Posterolateral instability of the knee: evaluation, treatment, results. Sports Med Arthrosc Rev. 2010;18(4):254–262, with permission).
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Figure 56-2
Combined hyperextension and varus mechanism of injury resulting in knee dislocation
(From Levy BA, Stuart MJ, Whelan DB. Posterolateral instability of the knee: evaluation, treatment, results. Sports Med Arthrosc Rev. 2010;18(4):254–262, with permission).
(From Levy BA, Stuart MJ, Whelan DB. Posterolateral instability of the knee: evaluation, treatment, results. Sports Med Arthrosc Rev. 2010;18(4):254–262, with permission).
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Frank dislocations are more often observed after motor vehicular and other high-energy trauma. Given the velocity at which most of these injuries occur, associated trauma—both locally at the joint and systemically—is the rule and can hamper prompt diagnosis and assessment of the knee. 
Lower energy mechanisms—such as those from sports participation—can give rise to isolated knee dislocations. These events are rare and often associated with contact sports. Obese patients have the potential to dislocate their knees with simple falls from a standing height.9,38,61 These “ultra-low” energy dislocations have a surprisingly high rate of associated neurovascular complications. Further complicating the management of these patients is the fact that standard braces and splints often do not fit appropriately and custom orthoses or long leg casts may be required to initially immobilize the injured limb. 

Associated Injuries with Knee Dislocations

Given the extent of force required to dissociate the femur and tibia, associated trauma to local joint and limb structures other than ligaments is the rule. Wascher et al.214 have reported the rates of an associated fracture at 57%, of multiple fractures at 41%, and of open fractures at 27% (Fig. 56-3). Fractures present specific problems to the identification and assessment of multiligament injuries as the inherent instability of the long bones can preclude performing an effective examination of the knee joint. Within the joint, damage to the cartilage and menisci is not uncommon, with one prospective series suggesting that this occurs in at least one third of patients.40 It is our observation that extensor mechanism disruption—while not specifically reported in frequency—can have disastrous functional sequelae given that restoration of the quadriceps mechanism is made exceptionally difficult in the setting of a highly unstable joint. 
Figure 56-3
Radiographic example of a knee dislocation with associated tibial and fibular fractures.
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The viability of the limb itself is threatened with associated vascular injury. The popliteal artery is at particular risk with knee dislocations because of its “tethered” position behind the joint; between the adductor hiatus proximally and the soleal arch distally, the vessel is relatively immobile and thus particularly susceptible to both traction and blunt injury. Blunt injuries are thought to occur with posterior dislocations secondary to direct compression by the tibia while traction injuries are more commonly ascribed to anterior dislocations. Estimates as to how often the popliteal artery is compromised following multiligament knee injury vary, but range as high as 50%, likely because of the inherent sensitivities of the investigations used to detect them.3,55,69,181,191,218 
Injury to the peroneal nerve can occur with traction or blunt trauma to the lateral side of the knee. In several large series, peroneal nerve palsy complicated knee dislocations at a frequency of approximately 25%.144,154,214 Recovery is observed in about half of these cases, most of which are partial peroneal nerve palsies.64,65,136 Dense motor and sensory palsies are rare but exceptionally dysfunctional for patients, as they mandate the permanent use of an ankle-foot orthosis or subsequent surgery to restore active dorsiflexion power to the foot and ankle, such as a partial tibial nerve transfer.63 Risk factors for associated peroneal nerve injury with knee dislocation have been identified, with predilection for males, patients with a high body mass index, and those with a concomitant fibular head fracture.154 Predictors for nerve recovery are lacking in the literature but currently under study. An unpublished series from the Mayo Clinic of 27 patients with 2- to 18-year follow-up demonstrated that only 37.5% of patients who sustained a complete peroneal nerve palsy in the setting of a multiligament knee injury recovered antigravity ankle dorsiflexion strength compared with 83.3% of those patients with a partial peroneal nerve palsy. This study also demonstrated significantly inferior functional outcomes compared with a matched cohort of knee dislocation patients who did not sustain a peroneal nerve injury.101 
Trauma to the head, chest, and/or abdomen is occasionally observed with high-energy knee dislocations. Wascher et al.214 reported that 27% of patients with a high-energy knee dislocation sustained life-threatening injuries. Such injuries can pose particular problems: extremity soft-tissue trauma can go unrecognized in intubated patients, management of systemic trauma can delay imaging and surgery for knee ligaments beyond a timely window, and patients may be unable to participate in functional rehabilitation programs because of mobility issues. Conversely, the severity of the knee derangement may divert the assessing physician’s attention away from other occult—but potentially serious—traumatic injuries. Given the high-energy nature of most knee dislocations, recognition of a multiligament knee injury should invoke an “ATLS-like” protocol for initial assessment of the patient, akin to that used for a patient with a femoral shaft fracture.135 
Furthermore, associated head injury has implications for both its tendency to stimulate the formation of heterotopic bone in the soft tissues and the impact cognitive dysfunction will have on the patient’s ability to understand and participate in rehabilitation.22,151 

Signs and Symptoms of Knee Dislocations

As has been stated previously, it is a rare occurrence that the knee will present in a dislocated state. Nonetheless, immediate reduction is essential in this instance to avoid the potential for prolonged neurovascular compromise. In most cases, in-line traction and subsequent extension will allow for reduction of the joint. The joint is usually most stable in an extended position also and can be immobilized in this position before proceeding with imaging. 
In the case of a reduced but acute multiligament knee injury, it falls upon the physician to piece together information from the mechanism of injury and the physical examination to determine whether the joint was subluxed or dislocated at some point and—if so—whether it remains “dislocate-able.” Unfortunately, the physical examination is often limited in this regard, as the limb will usually be exceptionally painful to move or manipulate in the awake patient. Moreover, capsular disruption is a frequent sequela of the joint dislocation and as a result, an effusion or a hemarthrosis may not be present. In such cases, it is essential to acquire an accurate history of the events surrounding the injury and maintain a high degree of suspicion throughout assessment. The examiner should carefully examine the skin for lesions that may give clues to the nature of the injury, such as prepatellar abrasions consistent with a “dashboard” injury. Rarely, incarceration of the medial capsule and even the medial collateral ligament (MCL) can prevent concentric reduction of the joint. In this case, the examiner may be alerted to the presence of an “irreducible” dislocation by the presence of skin dimpling on the medial aspect of the knee.212 Such cases require immediate open reduction (Fig. 56-4). 
Figure 56-4
Photographs of an irreducible knee dislocation.
 
(A) the medial skin “dimpling” and (B) the surface of the medial femoral condyle button-holed through the medial retinaculum immediately visible following skin incision.
(A) the medial skin “dimpling” and (B) the surface of the medial femoral condyle button-holed through the medial retinaculum immediately visible following skin incision.
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Figure 56-4
Photographs of an irreducible knee dislocation.
(A) the medial skin “dimpling” and (B) the surface of the medial femoral condyle button-holed through the medial retinaculum immediately visible following skin incision.
(A) the medial skin “dimpling” and (B) the surface of the medial femoral condyle button-holed through the medial retinaculum immediately visible following skin incision.
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Although a specific knee ligament examination may be less than fruitful in the acutely injured patient, serial examinations of the cruciate and collateral ligaments after a period of observation, immobilization, and ice application are essential. If the joint requires reduction, a subsequent examination under anesthesia should always be performed. In the acute phase, the integrity of the extensor mechanism must be determined as a priority, as should patellar position and stability. 
The assessor should also pay close attention to the presence of wounds that could communicate with the dislocated joint, as these mandate a modified protocol to include prompt extensive irrigation and debridement in addition to stabilization. Between 5% and 17% of knee dislocations are reported to be open.98 Open wounds in association with a multiligament injury indicate an extreme degree of soft tissue compromise. Given that the tissues deep within the joint have been disrupted by the dislocation, and that the entire surrounding soft tissue envelope including the skin has been compromised, open knee dislocations can be thought of as a “near complete” traumatic amputation. As such, the assessor should maintain a high degree of suspicion for the presence of associated trauma to nerves and blood vessels. 

Imaging and Other Diagnostic Studies for Knee Dislocations

Radiographs

In the acute setting, supine anteroposterior (AP) and lateral knee radiographs are obtained to evaluate the position of the tibiofemoral articulation. Oftentimes, subtle radiographic findings will also help the surgeon identify and understand ligamentous injury. For example, widening of the lateral joint space may be indicative of a lateral-sided injury, whereas medial joint space widening would indicate injury to the medial-sided structures. In the case of a posterior cruciate ligament (PCL)–deficient knee, the tibia is typically subluxed posteriorly relative to the femur (Fig. 56-5). 
Figure 56-5
 
Lateral radiograph showing posterior subluxation of the tibia consistent with knee dislocation and insufficiency of the posterior cruciate ligament.
Lateral radiograph showing posterior subluxation of the tibia consistent with knee dislocation and insufficiency of the posterior cruciate ligament.
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Figure 56-5
Lateral radiograph showing posterior subluxation of the tibia consistent with knee dislocation and insufficiency of the posterior cruciate ligament.
Lateral radiograph showing posterior subluxation of the tibia consistent with knee dislocation and insufficiency of the posterior cruciate ligament.
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Plain radiographs can also be used to assess for periarticular fractures that can be seen in the setting of a knee dislocation such as distal femur fractures, patella fractures, proximal tibia fractures, and tibial plateau fractures as well as extensor mechanism disruptions. Oftentimes, as well, tibial rim fractures will be noted on these views. Tibial rim fractures typically occur in the setting of knee dislocation when the femur rides over the front of the tibia and then spontaneously relocates, resulting in a small fracture of the anterior tibial plateau (Fig. 56-6). Rim fractures are typically treated nonoperatively but are often a sign of a more ominous knee injury and, when seen, should stimulate a careful investigation for associated soft tissue injuries. Associated injuries such as proximal tibiofibular injuries can sometimes accompany knee dislocation, especially with a high-energy mechanism, and may also be present on AP radiographs. An example of this is the so-called “arcuate sign.” The arcuate sign is a linear lucency through the head of the fibula best seen on AP radiographs and indicating a fibular head avulsion fracture.85,195 When present, this is pathognomonic for a posterolateral corner (PLC) injury. These “arcuate fractures” usually indicate bony avulsion of the distal fibular collateral ligament (FCL) and biceps femoris tendon attachment from the fibular head (Fig. 56-7). The AP radiograph may also provide clues to a patellar dislocation, which can be associated with a tibiofemoral dislocation. For example, a significantly lateralized patella will be a clue to this injury. 
Figure 56-6
Lateral radiograph showing a tibial rim fracture (arrow).
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Figure 56-7
 
A: AP and (B) lateral radiographs of a fibular head avulsion fracture indicating injury to the posterolateral corner of the knee.
A: AP and (B) lateral radiographs of a fibular head avulsion fracture indicating injury to the posterolateral corner of the knee.
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Figure 56-7
A: AP and (B) lateral radiographs of a fibular head avulsion fracture indicating injury to the posterolateral corner of the knee.
A: AP and (B) lateral radiographs of a fibular head avulsion fracture indicating injury to the posterolateral corner of the knee.
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In the chronic setting, 3 weeks or more after the injury, we typically obtain bilateral AP knee standing x-rays, bilateral posteroanterior flexion x-rays, a supine lateral x-ray, bilateral sunrise views, and bilateral hip to ankle radiographs. The bilateral AP and posteroanterior flexion views delineate any joint space narrowing indicative of osteoarthrosis and/or malalignment. The lateral radiographs are helpful for identifying arthritis and the positioning of the tibiofemoral and patellofemoral articulations. In addition, as noted previously, a chronic PCL-deficient knee will typically show posterior subluxation of the tibia relative to the femur. The sunrise views are obtained to assess the patellofemoral compartment and to identify any asymmetric findings consistent with associated patellofemoral dislocation or instability. Bilateral hip-to-ankle x-rays are obtained to assess for overall limb alignment. In the chronic setting, overall limb alignment is extremely important to define as it may have significant implications for success or failure of ligament reconstruction. For example, in the setting of an anterior cruciate ligament (ACL), PCL, and lateral-sided injury, varus deformity of the knee has been shown to be associated with a high rate of failure of a lateral-sided reconstruction.8 In those cases, a proximal tibial osteotomy is often required prior to any ligament reconstruction. 

Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) remains a gold standard imaging modality for ligamentous pathology. With the advent of 3-T MRI, high-definition images allow the assessment of all ligamentous structures about the knee, as well as cartilage lesions, meniscus pathology, and muscular and tendinous injuries, as well as capsular disruptions. With multiple separate planes (sagittal, coronal, axial, and oblique), a three-dimensional image of the disrupted structures can be obtained. MRI is very helpful at identifying not only a torn ligament but also the precise location of the ligament tear, which is very important to understand as it influences surgical decision making. For example, if the FCL is avulsed from the fibula, studies have shown reasonable success rates with repairing it directly back to bone.59,105 However, if a distal avulsion of the FCL is identified and there is also midsubstance signal change within the ligament, then reconstruction of the ligament is preferred. 
In addition to aiding in the diagnosis of ligamentous injuries, T1- and T2-weighted MRI can also be helpful in identifying fractures. Although not as valuable as radiographs or computed tomographic (CT) scan for bony definition, 3-T MRI does offer very good quality and detail of bony injury. Suffice it to say, in all knee dislocation and in multiligament injured knees, we recommend MRI to identify all pathology and facilitate surgical planning (Fig. 56-8). 
Figure 56-8
 
A: Sagittal T2 MRI showing ACL and PCL disruptions and (B) coronal view showing complete disruption of the superficial and deep MCL from its femoral attachment.
A: Sagittal T2 MRI showing ACL and PCL disruptions and (B) coronal view showing complete disruption of the superficial and deep MCL from its femoral attachment.
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Figure 56-8
A: Sagittal T2 MRI showing ACL and PCL disruptions and (B) coronal view showing complete disruption of the superficial and deep MCL from its femoral attachment.
A: Sagittal T2 MRI showing ACL and PCL disruptions and (B) coronal view showing complete disruption of the superficial and deep MCL from its femoral attachment.
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One important caveat in the radiographic evaluation of the acute knee dislocation is that at times when the tibiofemoral articulation cannot be maintained in adequate reduction, a spanning external fixator will be used to stabilize the knee. Whenever a spanning external fixator is used, it is important to know whether or not the fixator frame is magnetic resonance (MR) compatible. Most newer external fixator frames are MR compatible, but some are not. Therefore, whenever a spanning fixator is chosen to treat an acutely dislocated knee, it is important to choose an MR-compatible frame. It is important to understand that MRI with a spanning external fixator—even with an MR-compatible frame—does not allow high-definition resolution even in the best of circumstances. Therefore, obtaining an MRI will oftentimes be delayed until or repeated once the spanning fixator has been removed. 

Stress Radiographs

Stress radiography is another helpful tool in evaluating the dislocated knee as it provides an objective measurement of side-to-side differences in ligamentous laxity between the injured and uninjured knees. Side-to-side comparison of valgus stress films can be used to identify medial-sided injury, varus stress films can be used to identify lateral-sided injury, and finally posterior drawer stress views can be used to assess the integrity of the PCL. We typically perform stress radiography under fluoroscopic imaging. This allows the surgeon to obtain a perfect orthogonal view of the joint surfaces and more accurately assess the joint space. The medial and lateral tibial plateaus have different shapes with the medial plateau tending to be more concave and the lateral plateau more convex. For this reason, it is important when obtaining fluoroscopic stress views that the image intensifier is perfectly perpendicular to the joint surface in order to see a flat line at the tibial plateau margins. This makes comparison of side-to-side differences and side-by-side comparison with prior assessments more accurate (Figs. 56-9 and 56-10). Stress views are extremely helpful not only in measuring side-to-side differences but also in the setting of a globally unstable knee where all four ligaments are disrupted. In these cases, it is very difficult to determine the true degree of laxity on the medial and lateral sides and stress views will help delineate the exact amounts. 
Figure 56-9
Fluoroscopic varus stress imaging of (A) normal joint and (B) lateral joint space opening indicating lateral-sided injury
 
(From Levy BA, Stuart MJ, Whelan DB. Posterolateral instability of the knee: evaluation, treatment, results. Sports Med Arthrosc Rev. 2010;18(4):254–262, with permission).
(From Levy BA, Stuart MJ, Whelan DB. Posterolateral instability of the knee: evaluation, treatment, results. Sports Med Arthrosc Rev. 2010;18(4):254–262, with permission).
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Figure 56-9
Fluoroscopic varus stress imaging of (A) normal joint and (B) lateral joint space opening indicating lateral-sided injury
(From Levy BA, Stuart MJ, Whelan DB. Posterolateral instability of the knee: evaluation, treatment, results. Sports Med Arthrosc Rev. 2010;18(4):254–262, with permission).
(From Levy BA, Stuart MJ, Whelan DB. Posterolateral instability of the knee: evaluation, treatment, results. Sports Med Arthrosc Rev. 2010;18(4):254–262, with permission).
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Figure 56-10
 
Fluoroscopic valgus stress views of (A) normal joint and (B) medial joint space widening >10° in full extension indicative of ACL, PCL, MCL, and posteromedial corner injury.
Fluoroscopic valgus stress views of (A) normal joint and (B) medial joint space widening >10° in full extension indicative of ACL, PCL, MCL, and posteromedial corner injury.
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Figure 56-10
Fluoroscopic valgus stress views of (A) normal joint and (B) medial joint space widening >10° in full extension indicative of ACL, PCL, MCL, and posteromedial corner injury.
Fluoroscopic valgus stress views of (A) normal joint and (B) medial joint space widening >10° in full extension indicative of ACL, PCL, MCL, and posteromedial corner injury.
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The amount of side-to-side difference is important as the findings will often dictate surgical management. LaPrade et al.106 have shown that a side-to-side difference of greater than 2.7 mm of lateral joint space opening is indicative of an isolated FCL tear whereas more than 4 mm of side-to-side difference is consistent with injuries to both the FCL and the PLC. Similarly, LaPrade et al.102 also found that a side-to-side difference of 3.8 mm is indicative of an isolated MCL tear whereas a side-to-side difference of greater than 9.8 mm on average is indicative of a combined MCL and posteromedial corner (PMC) disruption. Additional biomechanical studies have shown that a grade II posterior drawer is consistent with isolate PCL injury whereas a grade III posterior drawer indicates combined PCL and PLC injury.177,179 In a cadaver study, Sekiya et al.179 found that, on average, 9.8 mm of posterior translation is indicative of an isolated PCL rupture, but with a combined PCL and PLC injury, the posterior drawer stress views showed a mean of 19.4 mm of posterior subluxation of the tibia relative to the femur. Similarly, Schulz et al.177 reported that posterior translation of more than 8 mm indicated complete insufficiency of the PCL while more than 12 mm of posterior translation suggested additional injury to the PLC structures. 
Stress views can also be used in the postoperative phase to determine clinical outcome. Side-to-side comparison with stress radiography is often utilized to objectively document success or failure of ligament surgery. 

Vascular Assessment

It is critically important to recognize that the dislocated knee is a limb-threatening injury with a high risk for vascular and neurologic compromise. The reported risk of vascular injury in the dislocated knee approaches 40% to 50%.3,55,69,181,218 Vascular injury is so common with knee dislocations due to the fact that the popliteal artery and vein are tethered by the adductor hiatus proximally and the tendinous arch of the proximal soleus distally. The ideal technique to screen for vascular injury is still under debate and many questions remain. Can one rely on physical examination alone? Is angiography required in all cases? And, what about other screening modalities such as ankle brachial indices (ABI), ultrasound, and CT or MR angiography? 
When there are “hard” signs of ischemia (i.e., a cool pulseless limb), and the zone of injury is known (knee dislocation/popliteal artery), then the vascular surgeon will often perform an immediate arterial exploration at the level of the knee without additional studies. If, however, the zone of injury is not well known, for example, a gunshot wound to the lower extremity with a large “blast zone,” then arteriography is typically performed to identify the location of the lesion.6,7 
In the setting of “soft” signs of ischemia where the limb may be slightly cooler or paler than the other but still have palpable, albeit potentially diminished, pulses, further arterial screening is mandated. Several authors have shown that palpable pulses can be noted in the presence of a major popliteal artery injury.57,153,171,187 While still controversial, palpable pulses alone do not rule out a significant vascular injury and, therefore, we recommend further screening for vascular injury in all documented or presumed knee dislocations (Fig. 56-11). 
Figure 56-11
Angiogram of patient with intact distal pulses showing (A) a complete popliteal artery occlusion with (B) collateral distal flow.
 
(From Levy BA, Boyd JL, Stuart MJ. Surgical treatment of acute and chronic anterior and posterior cruciate ligament and lateral side injuries of the knee. Sports Med Arthrosc Rev. 2011;19(2):110–119, with permission).
(From Levy BA, Boyd JL, Stuart MJ. Surgical treatment of acute and chronic anterior and posterior cruciate ligament and lateral side injuries of the knee. Sports Med Arthrosc Rev. 2011;19(2):110–119, with permission).
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Figure 56-11
Angiogram of patient with intact distal pulses showing (A) a complete popliteal artery occlusion with (B) collateral distal flow.
(From Levy BA, Boyd JL, Stuart MJ. Surgical treatment of acute and chronic anterior and posterior cruciate ligament and lateral side injuries of the knee. Sports Med Arthrosc Rev. 2011;19(2):110–119, with permission).
(From Levy BA, Boyd JL, Stuart MJ. Surgical treatment of acute and chronic anterior and posterior cruciate ligament and lateral side injuries of the knee. Sports Med Arthrosc Rev. 2011;19(2):110–119, with permission).
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One of the easiest methods to evaluate for vascular injury is the bedside measurement of the ABI. To obtain an ABI, a blood pressure cuff is placed at the level of the lower leg above the malleoli and bedside Doppler ultrasound is used to assess dorsalis pedis artery flow (Fig. 56-12). The blood pressure cuff is inflated and the systolic pressure as noted by the Doppler is identified. The same steps are repeated at the level of the arm and the ABI is a ratio of the ankle pressure to the brachial pressure. An ABI of 0.91 to 1.3 is considered normal. An ABI <0.90 requires further arterial screening.121 It is also important to note that patients with peripheral arterial disease may, in fact, have lower than normal ratios. So this factor needs to be considered in the acutely dislocated knee in the older patient population. Mills et al.133 have shown that an ABI of greater than 0.9 has shown 100% negative predictive value for a major arterial lesion. In other words, if the ABI is greater than 0.9, the odds of having a major arterial lesion approach 0%. Therefore, we recommend performing ABIs on all patients with a presumed or documented knee dislocation. 
Figure 56-12
Illustration of ankle brachial index measurement
 
(From Levy BA, Zlowodzki MP, Graves M, Cole PA. Screening for extremity arterial injury with the arterial pressure index. Am J Emerg Med. 2005;23(5):689–695, with permission).
(From Levy BA, Zlowodzki MP, Graves M, Cole PA. Screening for extremity arterial injury with the arterial pressure index. Am J Emerg Med. 2005;23(5):689–695, with permission).
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Figure 56-12
Illustration of ankle brachial index measurement
(From Levy BA, Zlowodzki MP, Graves M, Cole PA. Screening for extremity arterial injury with the arterial pressure index. Am J Emerg Med. 2005;23(5):689–695, with permission).
(From Levy BA, Zlowodzki MP, Graves M, Cole PA. Screening for extremity arterial injury with the arterial pressure index. Am J Emerg Med. 2005;23(5):689–695, with permission).
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CT angiography, which has been available since the 1990s, is now widely used as a screening tool for arterial injury (Fig. 56-13). It is less invasive than conventional arteriography because dyes are injected through the antecubital fossa as opposed to the femoral vein. It also exposes the patient to one-fourth the radiation of conventional arteriography and has been shown to have near 100% sensitivity and specificity.94,172 The only disadvantage to CT angiogram is the potential for an adverse reaction to contrast or—if contrast has already been used in other scans of the abdomen and pelvis—the potential for a toxic dye load. In cases where investigations requiring contrast have already been performed, a time frame of 4 to 6 hours is often necessary before performing a CT angiogram of the lower extremity. Thus, for polytrauma patients, CT angiogram may not be the ideal tool. Alternatively, if the patient is in the operating room for other reasons, intraoperative arteriography may be used to identify vascular injury of the lower limb. 
Figure 56-13
CT angiogram showing complete disruption of right popliteal arterial flow.
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Conventional arteriography has long been considered the gold standard for vascular assessment in complex knee trauma. Authors have demonstrated a sensitivity of 95% and specificity of 93%. However, a 5% to 7% false-positive rate has been identified, not to mention the fact that arteriography is fairly invasive and expensive and includes several risks including renal toxicity, pseudoaneurysm, and death from anaphylaxis.80,187 
Duplex ultrasonography has also been utilized as a noninvasive and quick arterial screening tool. It has been shown to have an excellent negative predictive value with a sensitivity of up to 90% but a specificity of only 68%. The other drawback to duplex ultrasonography is that it is technician-dependent and not all emergency departments have technicians available at all times to perform emergency studies.131,150 
Many vascular injuries that accompany a dislocated knee are not necessarily complete arterial occlusions but may, in fact, be intimal tears. Several authors have noted that the clinical course of intimal tears is fairly benign and therefore Stannard et al.191 recommend serial clinical examinations for patients with intimal tears. 
Our current recommendation for all patients with suspected or documented knee dislocation is to perform an ABI. If the ABI is greater than 0.9, we perform serial clinical vascular examinations every 2 to 4 hours for a 48-hour period. If the ABI is less than 0.9, we recommend a CT angiogram for further screening121,166 (Fig. 56-14). 
Figure 56-14
Mayo clinic algorithm for arterial injury screening (CTA, computed tomographic angiography)
 
(From Redmond JM, Levy BA, Dajani KA, Cass JR, Cole PA. Detecting vascular injury in lower-extremity orthopedic trauma: the role of CT angiography. Orthopedics. 2008;31(8):761–767, with permission).
(From Redmond JM, Levy BA, Dajani KA, Cass JR, Cole PA. Detecting vascular injury in lower-extremity orthopedic trauma: the role of CT angiography. Orthopedics. 2008;31(8):761–767, with permission).
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Figure 56-14
Mayo clinic algorithm for arterial injury screening (CTA, computed tomographic angiography)
(From Redmond JM, Levy BA, Dajani KA, Cass JR, Cole PA. Detecting vascular injury in lower-extremity orthopedic trauma: the role of CT angiography. Orthopedics. 2008;31(8):761–767, with permission).
(From Redmond JM, Levy BA, Dajani KA, Cass JR, Cole PA. Detecting vascular injury in lower-extremity orthopedic trauma: the role of CT angiography. Orthopedics. 2008;31(8):761–767, with permission).
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Classification of Knee Dislocations

Knee dislocations can be classified according to the direction of displacement or the anatomical structures (ligaments) damaged. A directional classification was first put forward by Kennedy et al.97 in 1963. Apart from the primary four types of dislocation corresponding to the direction of displacement of the tibia with respect to the femur (i.e., anterior, posterior, medial, and lateral), a fifth rotatory pattern was identified with four subtypes: anteromedial (AM), anterolateral (AL), posteromedial (PM), and posterolateral (PL). Complicating the directional classification is the recognition that most “dislocatable” knees will have spontaneously been reduced by the time of presentation. 
Because of the various factors making the use of a pure directional classification difficult, Schenck and colleagues have211 suggested that these injuries be classified according to the anatomic structures disrupted. A further modification by Wascher allows for the consideration of associated fractures.215 Most publications in the modern era have widely adopted this scheme, which has been made even more accurate with the incorporation of findings on MRI (Table 56-1). 
Table 56-1
Modified Schenck Classification System of Knee Dislocations
Classification Injury Description
KD I PCL intact knee dislocation with a functioning PCL and variable collateral involvement (usually lateral)
KD II Complete bicruciate injury with both collaterals intact (uncommon)
KD III An injury to both cruciate ligaments and one collateral ligament, either medial (M) or lateral (L)
KD IV An injury to both cruciate ligaments and both collateral ligaments
KD V A knee dislocation with periarticular fracture
 

An appended uppercase C indicates circulatory injury, an N denotes neurologic damage. For example, KD III-MC implies tearing of both cruciate ligaments and the medial collateral ligament, with an associated popliteal artery injury.

 

PCL, posterior cruciate ligament.

 

(From Wascher DC. High-velocity knee dislocation with vascular injury. Treatment principles. Clin Sports Med. 2000;19(3):457–477, with permission).

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Other classification systems have been developed specifically for FCL and PLC injuries.44,114 These classifications consider both the location of injury and the specific structures injured, including ligaments, soft tissue, and bony avulsions (Tables 56-2 and 56-3). 
Table 56-2
Fanelli Posterolateral Instability Classification of Knee Dislocations
Classification Injury Description Damaged Structures
PLI-A Increased tibial external rotation only PFL, popliteus tendon only
PLI-B Increased tibial external rotation and mild varus laxity (approximately 5 mm increased lateral joint line opening) PFL, popliteus tendon, attenuation of FCL
PLI-C Increased tibial external rotation and severe varus laxity (>10 mm increased lateral joint line opening) PFL, popliteus tendon, FCL, lateral capsular avulsion, cruciate ligament disruption
 

PLI, posterolateral instability; PFL, popliteofibular ligament; FCL, fibular collateral ligament.

 

(From Fanelli GC, Feldmann DD. Management of combined anterior cruciate ligament/posterior cruciate ligament/posterolateral complex injuries of the knee. Oper Tech Sports Med. 1999;7(3):144)

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Table 56-3
Boyd Classification of Posterolateral Corner Injuries in Knee Dislocations
Classification Injury Description
Type I Isolated ligamentous injury of the PLC, including the FCL, popliteus, or PFL
Type IIa Combined ligamentous injury of the PLC including injury to the distal FCL and biceps femoris, with either avulsion or fracture of the fibular head.
Type IIb Combined ligamentous injury of the PLC including injury to the FCL and popliteus, occurring at the proximal femoral origin.
Type IIIa Posterolateral corner knee injury with some combination of FCL (proximal, distal or midsubstance), popliteus (proximal, midsubstance, or musculotendinous), biceps femoris (distal, musculotendinous), posterolateral capsule, IT band.
Type IIIb PLC knee injury Type IIIa with unicruciate or bicruciate injury
 

PLC, posterolateral corner; FCL, fibular collateral ligament; PFL, popliteofibular ligament; IT, Iliotibial.

 

(From Levy BA, Boyd JL, Stuart MJ. Surgical treatment of acute and chronic anterior and posterior cruciate ligament and lateral side injuries of the knee. Sports Med Arthrosc. 19(2):111, with permission)

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Outcome Measures for Knee Dislocations

In broad terms, the spectrum of outcomes following multiligament knee injury will encompass those patients who have relatively stiff and painful joints as well as those who describe primarily residual instability and apprehension. The optimal outcome measure by which to assess these patients then would be one that captures functional data from these seemingly disparate profiles while avoiding significant floor and ceiling effects. In the absence of such a measure, investigators often employ a broad range of outcomes designed to capture stiffness (range of motion testing including contractures and flexion), laxity (KT-1000 measurement, Lachman’s test, pivot shift test, posterior drawer test), return to activity (preinjury employment and preinjury sporting activity) and functionality (Lysholm and IKDC scores). The practice of using so many different outcomes can be costly and time-consuming and lead to “responder burden” on behalf of study subjects. 
No current outcome measure is optimal, nor has one been previously validated for use specifically in those patients with multiligament knee injury. Reviews of relevant outcome studies (in patients with multiligament injured knees) that have utilized both the International Knee Documentation Committee (IKDC) and the Lysholm scores have revealed that there is often a discrepancy in functional outcome scores between these two measures. For example, in the retrospective series by Mariani et al., individuals who underwent a repair or reconstruction of their ligamentous structures had an average Lysholm score of 85, which has been defined as “good.”127 However, using the IKDC subjective score, only 25% of patients were able to achieve good or excellent results. Furthermore, there were no individuals in the repair group who were able to return to their preinjury level of sport. 
Currently available “knee specific” instruments lack the content necessary to evaluate patients with multiligament knee injuries. For example, the Lysholm and IKDC scores do not take into account the impact of associated polytrauma or of neurologic and vascular injuries often seen in this subset of patients. There appears to be a need for the development of a disease-specific quality of life instrument that is reliable, valid, and responsive and that can be utilized to distinguish the often vastly disparate outcomes experienced by patients who have had knee dislocations. 

Pathoanatomy and Applied Anatomy Relating to Knee Dislocations

The management of multiligament knee injury mandates a comprehensive understanding of the anatomy on all sides of the joint. Imperative to repair or reconstructive procedures is an intimate knowledge of the structure of the cruciate and collateral ligaments, as well as the complex confluence of structures that comprise the PMC and PLC. Reconstructing multiple ligaments simultaneously demands the surgeon be attentive to balancing the joint in several different planes, while avoiding “interference” among the individual reconstructive constructs. 
Beyond the ligamentous anatomy, the surgeon must also be aware of the potential for neurologic and vascular compromise—from both injury and treatment—that can often complicate multiligament knee injuries. A sound knowledge of the anatomy about the knee affords the greatest chance of success to restore stability while minimizing risk. 

Medial Side Knee Anatomy

The MCL complex was first dissected in detail by Brantigan and Voshell in the 1940s and is made up of three main components that blend into one; the superficial MCL, the deep MCL, and the posterior oblique ligament.16,17,126 An important concept to understand is the posteromedial corner, or PMC, which is a term for the medial anatomy posterior to the superficial MCL and extending to the PCL. The PMC is made up of the posterior oblique ligament (POL), the semimembranosus tendon (and its reflections), the oblique popliteal ligament, the posterior horn of the medial meniscus, and the medial joint capsule.171,206 
The superficial MCL originates from a depression slightly proximal and posterior to the medial femoral epicondyle, and has a broad, elongated insertion onto the proximal medial tibia (Fig. 56-15).104,185 A detailed anatomical dissection by LaPrade et al. showed that, on average, the superficial MCL takes origin 3.2 mm proximal and 4.8 mm posterior to the medial epicondyle of the femur; the tibial insertion is much more broad, attaching primarily to soft tissue proximally and to the bone of the tibia distally at a point approximately 60 mm from the joint surface.102 The deep MCL is a vertical thickening of the capsule, found underneath the superficial MCL, and sometimes separated from it by a bursa. Made up of distinct meniscofemoral and mensicotibial components, the deep MCL attaches just below the cartilage of the medial tibial plateau (Fig. 56-16). 
Figure 56-15
 
The medial side structures of the knee (MM, medial meniscus; SMCL, superficial medial collateral ligament; POL, posterior oblique ligament; SM, semimembranosus; MGN, medial head of the gastrocnemius).
The medial side structures of the knee (MM, medial meniscus; SMCL, superficial medial collateral ligament; POL, posterior oblique ligament; SM, semimembranosus; MGN, medial head of the gastrocnemius).
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Figure 56-15
The medial side structures of the knee (MM, medial meniscus; SMCL, superficial medial collateral ligament; POL, posterior oblique ligament; SM, semimembranosus; MGN, medial head of the gastrocnemius).
The medial side structures of the knee (MM, medial meniscus; SMCL, superficial medial collateral ligament; POL, posterior oblique ligament; SM, semimembranosus; MGN, medial head of the gastrocnemius).
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Figure 56-16
The osseous insertion sites for the medial side structures of the knee.
 
(ME, medial epicondyle; MPFL, medial patellofemoral ligament; AT, adductor tubercle; AMT, adductor magnus tendon insertion; GT, gastrocnemius tubercle; MGT, medial gastrocnemius tendon insertion; POL, posterior oblique ligament; sMCL, superficial medial collateral ligament.)
 
(From LaPrade RF, Engebretsen AH, Ly TV, Johansen S, Wentorf FA, Engebretsen L. The anatomy of the medial part of the knee. J Bone Joint Surg Am Vol. 2007;89(9):2000–2010, with permission).
(ME, medial epicondyle; MPFL, medial patellofemoral ligament; AT, adductor tubercle; AMT, adductor magnus tendon insertion; GT, gastrocnemius tubercle; MGT, medial gastrocnemius tendon insertion; POL, posterior oblique ligament; sMCL, superficial medial collateral ligament.)
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Figure 56-16
The osseous insertion sites for the medial side structures of the knee.
(ME, medial epicondyle; MPFL, medial patellofemoral ligament; AT, adductor tubercle; AMT, adductor magnus tendon insertion; GT, gastrocnemius tubercle; MGT, medial gastrocnemius tendon insertion; POL, posterior oblique ligament; sMCL, superficial medial collateral ligament.)
(From LaPrade RF, Engebretsen AH, Ly TV, Johansen S, Wentorf FA, Engebretsen L. The anatomy of the medial part of the knee. J Bone Joint Surg Am Vol. 2007;89(9):2000–2010, with permission).
(ME, medial epicondyle; MPFL, medial patellofemoral ligament; AT, adductor tubercle; AMT, adductor magnus tendon insertion; GT, gastrocnemius tubercle; MGT, medial gastrocnemius tendon insertion; POL, posterior oblique ligament; sMCL, superficial medial collateral ligament.)
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The posterior oblique ligament (POL) is an anatomically separate structure posterior to the superficial MCL, described in 1943, and named in 1973.17,89 Arising behind the medial femoral epicondyle, near the adductor tubercle, the POL fans out obliquely from the posterior aspect of the superficial MCL and inserts via three main arms; central, capsular, and superficial.104,170,185 The central arm is the largest, inserting near the margin of the articular surface of the tibia; the capsular arm reinforces the PM joint capsule and blends with the oblique popliteal ligament; while the superficial arm blends with the semimembranosus. Laprade et al.104 described the origin of the POL as being 7.7 mm distal and 6.4 mm posterior to the adductor tubercle, and 1.4 mm distal and 2.9 mm anterior to the newly described gastrocnemius tubercle. 
The MCL complex is dynamically reinforced by the pes anserinus, direct attachments of the vastus medialis to the superficial MCL, and by expansions of the semimembranosus tendon. The semimembranosus tendon (SM) has multiple attachments, including a direct PM tibial insertion, an expansion to the POL, an expansion to the popliteal fascia, and an insertion that passes deep to the superficial MCL to the anterior aspect of the tibia. It also forms the oblique popliteal ligament, which attaches to the fabella. The pes anserinus is made up of the sartorius, gracilis, and semitendinosus attachments to the tibia; they do so in a linear fashion from proximal to distal and insert proximally and anterior to the distal attachment of the superficial MCL. 

Medial Knee Anatomy—Function and Biomechanics

The MCL complex is a primary stabilizer that has both static and dynamic resistance (due to muscular attachments) to direct valgus stress. The MCL also provides constraint to external rotation and to anterior–posterior translation.126 Griffith et al.70 demonstrated that the proximal division of the superficial MCL is the primary static stabilizer to valgus motion at all angles of flexion while the deep MCL is an important secondary stabilizer. The distal division of the superficial MCL is the primary stabilizer for external rotation at 30°, while the POL is the primary stabilizer for internal rotation at all angles of flexion. 
The MCL also serves as a secondary stabilizer to AP motion; sectioning of the MCL with intact cruciates does not increase AP translation, but sectioning the superficial MCL in combination with the ACL increases the anterior translation compared to sectioning the ACL alone.76,198 This has also been demonstrated in clinical studies, with the use of computer navigation demonstrating increased AP laxity at 90° in patients with combined ACL and grade II MCL injuries, compared with patients with isolated ACL injuries.224 
The PMC is a primary stabilizer of the extended knee, providing one third of the restraint to valgus stress in extension, but slackening in flexion.170 The PMC also has a role as a secondary stabilizer to posterior translation, as sectioning both the POL and the PMC in a PCL-deficient knee increases posterior tibial translation in extension.156 Importantly, the PMC is a restraint to external rotation; sectioning studies have demonstrated that combined sectioning of the superficial and deep MCL in conjunction with the PMC increases tibial external rotation and anterior tibial translation at 30°—this phenomenon is known as AM rotatory instability (AMRI).87,88,145 Clinically this is detected by performing the anterior drawer test with the foot in external rotation; injury to the medial side of the knee allows anterior subluxation of the medial tibial plateau compared to the medial femoral condyle. 
A dynamic stabilizer of the medial side of the knee, the pes anserinus serves to reinforce the complex in extension, and prevents excessive external rotation of the tibia during flexion. In addition, it is thought that the semimembranosus tightens both the superficial MCL and the POL during active flexion, as well as retracting the medial meniscus; this action tightens the medial structures when they would normally be lax, preventing meniscal impingement. The important dynamic role of the pes anserinus and medial hamstring tendons should be considered when choosing grafts for high-grade medial sided ligamentous lesions; avoiding the harvest of autograft hamstring may be preferable in favor of other graft options in these cases. 

Medial Injury Patterns in Knee Dislocations

Twaddle et al.,208 in a series of 63 dislocated knees in 60 patients, demonstrated that an MCL injury was seen in 44% (28) of the knees. The majority of these injuries were distal avulsions. Although the PMC was not identified as a specific structural complex in this series, there was a significant proportion of knees identified with secondary injuries to the meniscocapsular, mensicofemoral, and meniscotibial attachments. 
An MRI study of 27 consecutive knee dislocations found that injury to at least one structure in the PMC was seen in 81% of cases, with injury to the superficial MCL detected in 63%.21 In this series, patients with high-grade laxity on examination had a high incidence of injury to the PMC and medial meniscus—suggesting the combined role of these structures in medial support. 
In a case series of 93 patients treated for symptomatic AMRI, 99% of the patients had an injury to the POL, 70% to the SM expansions, 33% to the superficial MCL, and 25% to the deep MCL.185 The POL and the superficial MCL had relatively equal incidences of injury to the tibial and femoral attachments; while it was not uncommon for the POL to have interstitial or multifocal injury, these patterns of injury were rarely seen with the superficial MCL. 
The close proximity of the insertions of the pes anserinus and superficial MCL create the potential for a “Stener-like lesion” to occur with tibial-sided MCL avulsions. Similar to the Stener lesion observed in thumb, the pes anserinus and its component tendons can become interposed deep to a superficial MCL that is pulled away from the tibia, usually the result of a profound valgus moment.28 The subsequent inability of the native ligament to heal to its anatomic attachment site has implications for prognosis and treatment—most surgeons will consider surgery in this scenario to reattach the avulsed ligament to the tibia and deep to the pes. 
Another unique injury pattern occasionally observed on the medial side with knee dislocations is that of the “irreducible” joint. First described in detail in the 1960s, this phenomenon occurs with PL dislocation of the tibia in the presence of an extreme valgus force.18,159 The force is such that the medial femoral condyle is forced through the knee capsule anteromedially. In this situation, the joint cannot be concentrically reduced via traditional manipulation techniques due to interposition of the medial soft tissue envelope (most commonly the medial joint capsule). Surgery should be performed emergently to reduce the joint (Fig. 56-17). 
Figure 56-17
 
A: Coronal MRI and B: Intraoperative photo demonstrating “button-holing” of the medial femoral condyle through the medial capsule with incarceration of the MCL and medial capsule in the joint preventing reduction (white arrow).
 
(Courtesy Robert G. Marx, MD).
A: Coronal MRI and B: Intraoperative photo demonstrating “button-holing” of the medial femoral condyle through the medial capsule with incarceration of the MCL and medial capsule in the joint preventing reduction (white arrow).
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Figure 56-17
A: Coronal MRI and B: Intraoperative photo demonstrating “button-holing” of the medial femoral condyle through the medial capsule with incarceration of the MCL and medial capsule in the joint preventing reduction (white arrow).
(Courtesy Robert G. Marx, MD).
A: Coronal MRI and B: Intraoperative photo demonstrating “button-holing” of the medial femoral condyle through the medial capsule with incarceration of the MCL and medial capsule in the joint preventing reduction (white arrow).
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From the series available then, MCL injuries are common in the setting of knee dislocations. Generalizations as to the location of the MCL disruptions (proximal vs. distal) are difficult to make given the relatively small numbers and inconsistent reporting. Associated injury to the PMC is likely more common than previously appreciated and accounts for significant laxity—particularly in rotation. Surgery is often required for tibial sided avulsions and interposed AM capsular disruptions with PL dislocations. 

Considerations in Repair and Reconstruction of Medial Knee Injury

While not addressing the technical aspects of medial repair and reconstructive procedures in detail (this will be done elsewhere in this chapter), most techniques involve a direct curvilinear medial approach and exposure. The main structures at risk on the medial side of the knee during such an exposure are the saphenous nerve and vein. Accompanied by the greater saphenous vein, the saphenous nerve descends along the medial side of the knee behind the sartorius, emerging between sartorius and gracilis to become subcutaneous; it is at this point that it gives off the infrapatellar branch, supplying the skin in front of the patella.139 

Lateral Side Knee Anatomy

Although PLC injuries in isolation occur in <2% of acute knee injuries, PLC injury in association with anterior and PCL tears occurs between 43% and 80% of the time.10,29,32,90,163 For this reason, an understanding of the complex ligamentous and musculotendinous anatomy is critical to the management of injury to this region of the knee. When considering repair and/or reconstruction after injury, the most important distinct anatomical structures to consider in the PLC are the popliteus tendon, the popliteofibular ligament (PFL), and the FCL, also referred to as the lateral collateral ligament (LCL) (Fig. 56-18). 
Figure 56-18
The posterolateral anatomy of the knee.
 
(LCL, lateral collateral ligament; PFL, popliteofibular ligament; LGN, lateral head of the gastrocnemius).
(LCL, lateral collateral ligament; PFL, popliteofibular ligament; LGN, lateral head of the gastrocnemius).
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Figure 56-18
The posterolateral anatomy of the knee.
(LCL, lateral collateral ligament; PFL, popliteofibular ligament; LGN, lateral head of the gastrocnemius).
(LCL, lateral collateral ligament; PFL, popliteofibular ligament; LGN, lateral head of the gastrocnemius).
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Similar to the medial side of the knee, exposure laterally usually proceeds via a curvilinear incision. The iliotibial band (ITB) is the first structure encountered in the approach, and it has three components: superficial, deep, and capsulo-osseous.174 The superficial fibers of the ITB run from the anterior superior iliac spine and anterior iliac crest to insert on the AL aspect of the lateral tibial plateau, or Gerdy’s tubercle; it is rarely injured in disruption of the PLC of the knee. The deep layer runs from the medial aspect of the superficial ITB to the lateral intermuscular septum, while the capsulo-osseous layer runs from the lateral intermuscular septum to blend with the short head of the biceps femoris, forming an AL sling over the lateral femoral condyle.123,202,204 
The biceps tendon is composed of both short and long heads; its primary function is to flex the knee and externally rotate the flexed knee. The long head takes origin from the ischial tuberosity, while the short head originates from the medial aspect of the linea aspera of the distal femur.139 The direct arm of the long head inserts onto the PL aspect of the fibular styloid, with an anterior arm that passes lateral to the FCL to insert onto the tibial plateau.204 The short head also has multiple tendinous arms; an anterior arm that passes deep to the FCL to attach to the meniscotibial capsule, a direct arm to the fibular styloid, and a capsular arm to the PL capsule. Avulsion of the anterior arm is seen with ACL injuries and may cause a Segond fracture. It is the direct arm that can give rise to fibular head avulsions—seen commonly in AM dislocations and high-grade varus knee injuries. The most distal edge of the capsular arm of the biceps forms the fabellofibular ligament—a component structure of the PLC.112,203,204 
The FCL arises from the femur in a small depression just proximal and posterior to the lateral epicondyle (mean 1.4 mm proximal and 3.1 mm posterior) (see Fig. 56-18).109 The ligament is approximately 70 mm long and extracapsular and runs distally to insert onto the lateral fibular head; the insertion is a mean of 8.2 mm posterior to the anterior border, and 28.4 mm anteroinferior to the proximal tip of the fibular styloid.103,204 
The popliteus complex consists of the popliteus muscle and tendon and multiple ligamentous connections; it acts as a dynamic internal rotator of the tibia. The popliteus muscle originates from the posteromedial aspect of the proximal tibia, forming the floor of the inferior popliteal fossa, and becomes the popliteal tendon at the lateral one third of the fossa. The tendon’s average length is 54 mm; passing through the popliteal hiatus in the coronary ligament, it becomes intra-articular and inserts into the popliteal sulcus of lateral femoral condyle, consistently in the proximal half and anterior one-fifth of the sulcus.109,193 The popliteus tendon insertion is anterior and distal to the femoral insertion of the FCL (18.5 mm anterior and distal to the femoral insertion of FCL, 15.8 mm anterior and distal to the lateral epicondyle of the femur.193,204 The popliteus also has multiple attachments to the tibia, fibula, and meniscus; the meniscal attachments act to dynamically stabilize the lateral meniscus. The fibular attachments are known as the anterior and posterior PFLs (previously the arcuate ligament). 
The PFL is a continuation of the popliteus tendon, present in between 94% and 100% of knees; it is a static stabilizer, resisting varus, external rotation, and posterior tibial translation.112,130,217 Arising from just proximal to the musculotendinous junction of the popliteus, it consists of anterior and posterior divisions attaching to the fibular in a “Y” configuration.109 The posterior division is stronger and attaches to the apex and downslope of the PM fibular styloid process (1.6 to 2.8 mm distal to the PM tip of the fibular styloid) while the anterior division attaches just medial to the FCL. In PLC injuries, the posterior division may avulse a fragment of the fibular head known as an arcuate fracture, and it is this larger, posterior division of the PFL that is usually reconstructed in PLC injuries.109,174 
The fabellofibular ligament is the most distal edge of the capsular arm of the biceps femoris, running from the lateral edge of the fabella (osseous in 10% to 20% of knees) to the fibular head just behind the posterior division of the PFL.112,161 The fabellofibular ligament is tightest in full extension and likely provides stability in this position. The PL capsule has superficial and deep laminae, which become one layer anterior to the ITB. There is commonly a thickening of the middle third of the lateral capsule, in a manner similar to the deep MCL; it is composed of both meniscofemoral and meniscotibial components and is a secondary stabilizer to varus instability. Injury to the meniscotibial component is responsible for the bony avulsion fracture known as the Segond fracture. The arcuate ligament is a Y-shaped condensation of the PL capsule of varying thickness, present in a variable percentage of knees; some fibers pass to the tip of the styloid process. 

Lateral Knee Anatomy—Function and Biomechanics

The primary functions of the PLC are to resist varus rotation, external tibial rotation, and posterior translation of the tibia. The most important structures in imparting stability are the FCL, the popliteus tendon, and the PFL.66,72,103,174 The FCL is the primary static stabilizer to varus forces at all flexion angles of the knee, especially between 0° and 30° of flexion, with the PLC and PCL important secondary stabilizers.103,174 
The popliteus complex, in conjunction with the FCL, provides primary restraint to external rotation of the knee. Sectioning of the PLC increases external rotation at all angles of knee flexion.66 The FCL primarily resists external rotation early in knee flexion (0° to 30°). The popliteus tendon and the PFL become more highly loaded with external rotation at knee flexion angles of greater than 60°.111 Sectioning of the PLC in the PCL intact knee increases external rotation at 30° more than at 90°, and combined sectioning of the PLC and the PCL results in increased external rotation at all angles of knee flexion and maximally at 90°; this is the basis of the clinical dial test.66,72 
The PCL is the dominant restraint to posterior tibial translation; however, it has been observed that reconstructing the PCL only in PCL- and PLC-deficient knees results in increased residual posterior tibial translation.78 Sectioning of the PL structures with the PCL intact increases the posterior translation of the lateral tibial plateau in extension; in the PCL-deficient knee, such sectioning increases posterior translation at 30° and 90°. In fact, at 90° isolated PCL sectioning generates between 5 and 11 mm of laxity; combined sectioning of the PCL and PLC generates up to 15 to 21 mm of laxity. Clinically, a grade 3 PCL deficiency can be observed only if the PLC is also deficient.179 
While the PLC does not prevent primary anterior tibial translation, in the ACL-deficient knee it becomes an important restraint, especially in extension. This function is seen in the setting of an ACL-deficient knee with a torn PLC, examination will often reveal a markedly positive Lachman test with only a subtle anterior drawer.222 

Lateral Injury Patterns in Knee Dislocations

The incidence of injury to the PLC in the multiple ligaments-injured knee is high. In a series by Karataglis et al., 73% (27/37) of the knee dislocations had an associated PLC injury.96 In 89 patients, all of whom had both ACL and PCL ruptures, the incidence of FCL rupture was 38% (34/89).167 Not all components of the PLC are injured in every case; in a series of 89 consecutive patients treated surgically for knee dislocation, 32% had a FCL injury, 31% had a popliteus injury, and 12% had a biceps tendon injury.81 
The location of the ligament injuries is also variable and may be proximal, distal, or midsubstance. Feng et al.,48 in a series of 48 acute grade III PLC injuries undergoing surgery, showed that 40% of patients (19/48) had femoral avulsions of the popliteus, the FCL, or both. 
The common peroneal nerve (CPN) is extremely vulnerable to injury in knee dislocation, due to the fact that it is tethered proximally at the fibular neck and distally at the intermuscular septum. CPN injury is most commonly associated with injury to the PLC.2,30,64 The overall rate of neurologic injury following knee dislocation is as high as 40%, with complete motor and sensory disruption of the CPN reported in 19% of patients in some series; it is usually a traction injury occurring over a substantial length of the nerve.148,154,167 Recovery is related to the severity of the initial injury, and while patients with incomplete injuries have a better prognosis, only 40% or less of patients with CPN injuries will experience functional recovery.136 
The arcuate sign is a term referring to avulsion fractures of the proximal fibula seen on radiographs. In a series of 18 knees with arcuate sign on radiographs, MRI confirmed that in every case the FCL, biceps femoris, or both were attached to the bony fragment, with an associated injury to at least one of the cruciate ligaments detected in 89% of knees.95 

Considerations in Repair and Reconstruction of Lateral Knee Injury

The CPN is found deep and posterior to the biceps tendon and runs around the lateral aspect of the fibular head 1.5 to 2 cm distal to the fibular styloid at the level of the fibular neck. It should be the first structure identified and protected during a dissection of the PLC. The inferior lateral geniculate artery runs along the posterior joint capsule at the superior edge of the lateral meniscus, between the superficial and deep layers of the PL capsule; at the top of the fibular styloid, it is found between the popliteofibular and fabellofibular ligaments. 

Posterior Anatomy of the Knee

The anatomy of the posterior aspect of the knee is a complicated network of dynamic and static stabilizers; these structures include the PCL, capsule, and the multiple attachments of the SM and popliteus muscles.110 
The PCL is the largest of the intra-articular ligaments, with an average length of 38 mm, and a mean diameter at the midpoint of 13 mm; its cross-sectional area is approximately 120% to 150% greater than that of the ACL.15 Arising from the lateral aspect of the medial femoral condyle, and inserting onto the posterior tibia, the PCL is most narrow in its midsubstance, fanning out at both the femoral origin and the tibial insertion. The PCL has two distinct bundles defined by their insertion on the femur: an AL bundle and a PM bundle. The AL bundle is larger and comprises 85% of the PCL’s cross-sectional area. 
The femoral footprint is a broad, semicircular attachment on the AL aspect of the medial femoral condyle, adjacent to the articular surface. In the coronal plane, this attachment is typically between 12 and 4 o’clock in the right knee, and between 12 and 8 o’clock in the left knee; insertion of the two bundles is separated by a medial bifurcate ridge53,132 (Fig. 56-19). 
Figure 56-19
 
Sagittal photograph of a sectioned cadaver femur showing the anatomic insertions of the PCL onto the medial femoral condyle (from Edwards A, Bull AM, Amis AA. The attachments of the fiber bundles of the posterior cruciate ligament: an anatomic study. Arthroscopy. 2007;23(3):284–290, with permission).
Sagittal photograph of a sectioned cadaver femur showing the anatomic insertions of the PCL onto the medial femoral condyle (from Edwards A, Bull AM, Amis AA. The attachments of the fiber bundles of the posterior cruciate ligament: an anatomic study. Arthroscopy. 2007;23(3):284–290, with permission).
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Figure 56-19
Sagittal photograph of a sectioned cadaver femur showing the anatomic insertions of the PCL onto the medial femoral condyle (from Edwards A, Bull AM, Amis AA. The attachments of the fiber bundles of the posterior cruciate ligament: an anatomic study. Arthroscopy. 2007;23(3):284–290, with permission).
Sagittal photograph of a sectioned cadaver femur showing the anatomic insertions of the PCL onto the medial femoral condyle (from Edwards A, Bull AM, Amis AA. The attachments of the fiber bundles of the posterior cruciate ligament: an anatomic study. Arthroscopy. 2007;23(3):284–290, with permission).
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The PCL inserts onto a midline depression on the tibia, 10 to 15 mm below the level of the medial and lateral tibial plateaus; this fossa is trapezoidal in shape.15 The AL bundle occupies the superolateral aspect of the tibial footprint, with the PM occupying the inferomedial aspect of the intercondylar fossa.199 (Fig. 56-20). Accompanying the PCL are the meniscofemoral ligaments, at least one of which is present in 93% of knees; these lie anterior (ligament of Humphrey) and posterior (ligament of Wrisberg) to the PCL.74 Contributing significantly to the PCL footprint and cross-sectional area (mean 17.2% in one cadaver study), the meniscofemoral ligaments connect the posterior horn of the lateral meniscus to the intercondylar notch, and are thought to be secondary restraints to posterior translation, as well as acting to stabilize the posterior horn of the lateral meniscus.113,143,158 However, the degree to which these ligaments contribute to knee stability is currently unknown. 
Figure 56-20
 
A: Axial and (B) posterior photographs of a cadaver knee showing the anatomic insertions of the PCL onto the PCL facet of the tibia.
 
(From Edwards A, Bull AM, Amis AA. The attachments of the fiber bundles of the posterior cruciate ligament: an anatomic study. Arthroscopy. 2007;23(3):284–290, with permission)
A: Axial and (B) posterior photographs of a cadaver knee showing the anatomic insertions of the PCL onto the PCL facet of the tibia.
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Figure 56-20
A: Axial and (B) posterior photographs of a cadaver knee showing the anatomic insertions of the PCL onto the PCL facet of the tibia.
(From Edwards A, Bull AM, Amis AA. The attachments of the fiber bundles of the posterior cruciate ligament: an anatomic study. Arthroscopy. 2007;23(3):284–290, with permission)
A: Axial and (B) posterior photographs of a cadaver knee showing the anatomic insertions of the PCL onto the PCL facet of the tibia.
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The posterior joint capsule originates at the proximal margin of the posterior femoral condyles and attaches below the tibial plateau; it is continuous medially with the superficial MCL and the POL.110 There is commonly a variably sized defect in the PM joint capsule, between the medial head of the gastrocnemius and the direct attachment of the SM; this is likely the cause of Baker’s cysts. In addition to its contribution to the medial aspect of the knee, the semimembranosus has multiple extensions to the posterior aspect of the knee; these include proximal posterior capsular arms, distal tibial expansions, and its contributions to the oblique popliteal ligament. The oblique popliteal ligament is a distinct thickening of the capsule, arising medially as a confluence of an SM expansion and an arm of the POL. Usually 48 mm long and widening from 9.5 mm medially to 16.4 mm at its lateral attachment, it attaches to both the fabella and the posterior tibia just lateral to the PCL; the ligament did not attach to the lateral femoral condyle in any of the 20 knees dissected by Laprade et al.110 The posterior capsule is also strengthened by an expansion from the medial aspect of the popliteus that attaches to the PM joint capsule (Fig. 56-21). 
Figure 56-21
 
Deep anatomy of the posterior aspect of the knee (SM, semimembranosus; OPL, oblique popliteal ligament; LCL, lateral collateral ligament; PCL, posterior cruciate ligament).
Deep anatomy of the posterior aspect of the knee (SM, semimembranosus; OPL, oblique popliteal ligament; LCL, lateral collateral ligament; PCL, posterior cruciate ligament).
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Figure 56-21
Deep anatomy of the posterior aspect of the knee (SM, semimembranosus; OPL, oblique popliteal ligament; LCL, lateral collateral ligament; PCL, posterior cruciate ligament).
Deep anatomy of the posterior aspect of the knee (SM, semimembranosus; OPL, oblique popliteal ligament; LCL, lateral collateral ligament; PCL, posterior cruciate ligament).
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Posterior Knee Anatomy—Function and Biomechanics

The PCL provides the majority of the total restraint to posterior tibial displacement at all flexion angles, and 95% of the posterior stability between 30° and 90°.20,66 It is likely that the larger AL bundle is the major contributor, with biomechanical tests demonstrating that the AL bundle has a tensile strength of 1620 N compared with 258 N of the PM bundle.160 However, at flexion angles beyond 120°, the PM bundle becomes horizontal, suggesting increased function of the PM bundle with increased knee flexion.1 
As previously mentioned, the PCL is a secondary restraint to varus rotation; while sectioning the PCL alone does not increase varus rotation, doing so in addition to sectioning the PLC significantly increases varus rotation.66,72 In the same manner, the PCL is a secondary restraint to valgus rotation; again sectioning of the PCL with an intact FCL does not affect varus rotation.174 The PCL also acts as a secondary restraint to both internal and external rotation of the tibia, with sectioning mildly increasing the range of external rotation at 30° and 90° and of internal rotation at 90°. The function of the OPL has only recently become clearer. A cadaver study by Morgan et al.141 showed that the OPL was the primary ligamentous restraint to knee hyperextension; in all groups the increase in knee hyperextension after sectioning the OPL approached or exceeded the increases seen after sectioning the ACL and PCL combined. Whether surgical repair or reconstruction is indicated in patients with knee hyperextension after knee dislocation remains to be seen. 

Posterior Injury Patterns in Knee Dislocations

The incidence of PCL injury in the multiply ligament injured knee is very high, but the pattern of injury varies. In a series of 63 knee dislocations, the incidence of PCL injury was 87%, with the majority being proximal avulsions or midsubstance tears; only 5% were distal avulsions.208 In a separate study, Richter et al.167 operated on 68 knee dislocations with PCL injury; the most common patterns of injury were intrasubstance ruptures (37%), tibial avulsion without bone (28%), and femoral avulsion without bone (18%). Femoral bony avulsion (7%) and tibial bony avulsion (10%) were less common. 
The pattern of injury is important to recognize in PCL injury, as some may be amenable to primary repair. In the series by Twaddle et al.,208 46% of the PCLs were avulsed from the femur and were repaired. Isolated distal PCL avulsions with a bony fragment are frequently repaired, either through an open approach or by arthroscopic means—while this pattern seems relatively uncommon, primary repair of such lesions has been described in the knee dislocation population, but not usually via a posterior approach.11,73,148,167 
Becoming the popliteal artery after the femoral artery passes through the hiatus of the adductor magnus, it usually divides into the anterior and posterior tibial arteries at the lower border of the popliteus but can divide more proximally with the anterior tibial artery passing anterior to the popliteus.139 The popliteal artery is specifically at risk during the initial trauma of knee dislocation, as it is tethered proximally by the tendinous insertion of the adductor magnus onto the medial femoral epicondyle and distally by the tendon of the soleus. Relative displacement of the tibia posteriorly in posterior dislocations—or of the femur posteriorly in anterior dislocations—can result in either a traction or blunt injury to the artery at its “fixed” segment (Fig. 56-22A). The severity of injury can vary from an intimal flap to complete transection of the vessel, although the former is often more sinister in its clinical implications. Collateral flow can often perfuse the limb distally in cases of acute partial injury or intimal flaps but is insufficient to maintain flow in the long term or at times of increased demand. Disruptions of popliteal flow demand a high index of suspicion, early recognition, and often vascular surgery for either repair or bypass. 
Figure 56-22
 
Illustrations of popliteal artery anatomy; A: The course of the popliteal artery behind the knee. Note the “fixation’ points proximally at the adductor hiatus and distally at the soleal arch that put the artery at risk during injury. B: The popliteal artery at risk during surgery. (AM, adductor magnus).
Illustrations of popliteal artery anatomy; A: The course of the popliteal artery behind the knee. Note the “fixation’ points proximally at the adductor hiatus and distally at the soleal arch that put the artery at risk during injury. B: The popliteal artery at risk during surgery. (AM, adductor magnus).
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Figure 56-22
Illustrations of popliteal artery anatomy; A: The course of the popliteal artery behind the knee. Note the “fixation’ points proximally at the adductor hiatus and distally at the soleal arch that put the artery at risk during injury. B: The popliteal artery at risk during surgery. (AM, adductor magnus).
Illustrations of popliteal artery anatomy; A: The course of the popliteal artery behind the knee. Note the “fixation’ points proximally at the adductor hiatus and distally at the soleal arch that put the artery at risk during injury. B: The popliteal artery at risk during surgery. (AM, adductor magnus).
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The reported rate of injury to the popliteal artery ranges between 7% and 32% in knee dislocations, with a mean of 30%.68 Direct injury is thought to be more common in posterior dislocations due to the posterior displacement of the tibia; however, Wascher et al.214 found that the direction of the knee dislocation did not predict the presence of an arterial injury. 

Considerations in Repair and Reconstruction of PCL Injury

The popliteal artery is specifically at risk when drilling the tibial tunnel in arthroscopic PCL reconstructions, as the anterior wall of the popliteal artery is only 7 to 10 mm from the posterior aspect of the PCL162 (Fig. 56-22B). Direct open posterior exposure of the PCL has been described for both repair of tibial avulsions or “inlay” type reconstructions. Traditionally, the posterior neurovascular bundle was formally exposed and retracted using a long curvilinear posterior incision before addressing the ligamentous injury. A more limited exposure described by Burks and Schaffer19 affords exposure of the tibial footprint utilizing the muscular interval between the medial head of the gastrocnemius and semimembranosus. This approach can be performed through a smaller distal curved incision with the neurovascular structures being protected by a laterally retracted medial gastrocnemius; structures at risk in this approach include the middle geniculate artery that often needs ligation, and the motor branch of the tibial nerve to the medial head of the gastrocnemius. 

ACL Anatomy

The ACL is an intra-articular ligament, but technically extrasynovial as it is surrounded by synovium. Running from the femur to the tibia in an anterior–medial direction, the ACL has both a variable length (22 to 41 mm) and width (7 to 12 mm), although it is consistently narrowest in the midsubstance.4,35,77 The ACL is made up of two bundles, the AM and the PL, which are named according to their tibial insertion.62 
The femoral origin of the ACL is on the PM edge of the lateral femoral condyle, posterior to the lateral intercondylar ridge (also known as Resident’s ridge). The attachment is usually oval in shape, with the AM bundle arising from the superior and anterior aspects and the PL bundle arising from the posterior and inferior aspects.12 Anatomically, these bundles are often separated by the lateral bifurcate ridge, which runs from anterior to posterior on the femur.49 Using a clock-face description, based on the posterior outlet of the femoral intercondylar notch, Edwards et al.37 found that the bulk of the AM bundle was attached between 9.30 and 11.30 o’clock and the PL bundle between 8.30 and 10 o’clock. The distance on the femur between the centers of these two bundles varies from 8 to 10 mm, depending on the size of the knee.225 
The tibial footprint of the ACL is on the tibial plateau, in the anterior intercondylar fossa, between the medial and lateral tibial spines; the tibial insertion is 120% larger than the femoral insertion.77 This insertion is AL to the medial tibial spine, with some fibers passing deep to the transverse meniscal ligament, and some merging with the anterior aspect of the lateral meniscus.12 Generally, the AM bundle attaches to the AM portion, and the PL bundle attaches to the PL portion, as their names suggest; however, there is some anatomical variation. With regard to anatomical localization of the tibial footprint, the most commonly used landmarks are the anterior aspect of the PCL (between 7 and 10.4 mm anterior to the PCL), the posterior border of the anterior horn of the lateral meniscus (aligned with the center of the AM bundle), and the medial tibial spine (center of the PL bundle is 4 ± 1 mm and the center of the AM bundle is 5 ± 1 mm from this landmark).36,93,140 

ACL Function and Biomechanics

The ACL provides the primary resistance to anterior tibial translation; it also guides rotation of the tibia during the screw-home mechanism.51 In extension, the PL bundle is tight, and the AM bundle somewhat lax; as the knee flexes, the ACL becomes more horizontal, causing the more vertically orientated PL bundle to loose tension while the more horizontal AM bundle tightens.4 This has been shown to correspond to the respective mechanical function of each bundle, with the PL bundle resisting anterior tibial translation in extension, and the AM bundle becomes more important as flexion increases, carrying a higher force than the PL bundle beyond 45° of flexion. It has also been demonstrated that internal rotation places strain on the ACL, and that the ACL-deficient knee has increased internal tibial rotation compared with the ACL-intact knee; it is likely that the PL bundle plays the most significant role in this respect.5,52,58 

ACL Injury Patterns in Knee Dislocations

Richter et al.167 reported on the pattern of injury of the ACL in traumatic knee dislocations; 32% (22/68) were intraligamentous ruptures, 24% (16/68) were femoral avulsions without bone, and 26% (18/68) were tibial avulsions without bone. Similar to the pattern of injury noticed with the PCL, femoral avulsion with bone (7%) and tibial avulsion with bone (10%) were relatively uncommon patterns. 

Knee Dislocation Treatment Options

Following reduction of the dislocated knee joint, the goals of initial management are to diagnose and treat limb-threatening injuries. In the absence of concomitant diagnoses requiring urgent surgical management, such as open dislocations, irreducible dislocations, vascular injury, or compartment syndrome, the goal of definitive management is to provide a pain-free and functional knee through restoration of ligamentous stability and range of motion. 
Traditionally, immobilization was the mainstay of management for the reduced knee dislocation.3,194,200 Protocols called for a long leg cast or brace to promote early stiffness initially in the weeks following injury, followed by a program of prolonged therapy to restore strength and motion over subsequent months. The philosophy at the time was that a stiff joint would be less likely to redislocate, albeit with some residual functional limitations. 
More recently, acute surgical repair and/or reconstruction has been advocated as a potential means to restore stability early while affording motion and minimizing the potential for muscle weakness and atrophy.194 The advent of arthroscopic surgery and minimally invasive techniques and the utilization of allograft tissue and the evolution of ligament fixation devices have added further enthusiasm to the early surgery movement. 
Several comparisons of these two disparate treatment philosophies—prolonged immobilization to promote stiffness versus early surgery to prevent loss of motion and strength—have been published. Dedmond and Almekinders31 reviewed the literature available prior to 2000 identifying 17 studies that described treatment for 206 knee dislocations (132 operative and 74 nonoperative). Average range of motion and Lysholm scores were significantly superior in the operative group. In a review of studies published after 2000, and up to 2011, Peskun and Whelan155 identified a further 35 studies describing 916 dislocations, the vast majority of which were treated operatively representing the shift in philosophy over time (855 operative vs. 61 nonoperative). Again the superiority of operative treatment was demonstrated when considering a broader range of outcomes including functional outcome, stability, and motion, as well as return to sports and work. 
There have also been studies, albeit retrospective, that have directly compared groups of patients treated operatively and nonoperatively at the same centers.157,167 Richter et al.167 reported on 89 patients with knee dislocations treated at a single level 1 trauma center. At an average follow-up of more than 8 years, surgical repair or reconstruction of the ligaments (63 patients) was superior to nonsurgical treatment (26 patients). Functional rehabilitation—which comprised early range-of-motion exercises—was identified as the single most important prognostic factor. Plancher and Siliski157 found that operatively treated patients were not only better from a functional standpoint but also less likely to develop severe radiographic degenerative changes. 

Nonoperative Management of Knee Dislocations

Despite the relative abundance of recent information suggesting the superiority of operative treatment for knee dislocations and multiligament knee injuries in general, there are times when surgery may not be possible or is strongly contraindicated. Such instances would include—but are not limited to—those patients with substantial comorbidities or polytrauma in whom the risk of operative intervention likely outweighs the benefit. These types of circumstances are not uncommon with knee dislocations. As mentioned previously, life-threatening polytrauma is associated with high-energy mechanism knee dislocations in approximately 27% of cases.214 Moreover, multiligament knee injury can occur with minimal trauma in obese individuals (the “ultra-low” energy knee dislocation),9,38,61 many of whom have concomitant medical conditions that preclude a general anesthetic. In those with significant open wounds, the implantation of allograft tissue for reconstruction of torn knee ligaments may be too dangerous, given the risk of contamination and potential infection. 
The role of surgical reconstruction in skeletally immature and elderly patients with knee dislocations is unknown. In the elderly, there is obvious risk imposed by comorbidity. Complicating matters further are the technical difficulties presented by poor bone quality and the unpredictability of surgical reconstruction of ligamentous injury in those with any degree of preexisting arthritis. Although techniques have been described to surgically treat children with open growth plates,14,54,86,165,210 the complex constructs described for reconstruction of multiligament injuries—especially those with several tibial tunnels—significantly increase the chance for growth disturbance. 

Immobilization

Nonoperative care begins initially with reduction of the joint and observation for vascular injury, nerve injury, or developing compartment syndrome. Assuming that there are no concomitant limb-threatening injuries or open wounds, and the joint remains concentrically reduced, the knee is immobilized in full extension in a long leg cylindrical cast (or splint) for at least 3 weeks.71,200 The period of immobilization may be extended as long as 6 weeks, depending on the extent of the original injury and the treating physician’s impression of the degree of ligamentous laxity persisting at 3 weeks. Immobilization for longer than 6 weeks is not recommended.200 The goal of nonoperative care is the “titration” of a sufficient amount of stiffness so that the joint will remain reduced but will maintain a functional arc of motion. Following the initial period of immobilization, range-of-motion exercises are introduced and progressed until these goals are met. 

External Fixator

Occasionally the application of an external fixator may be required to maintain reduction of a highly unstable joint (Fig. 56-23). While this procedure requires a general anesthetic, it is not nearly as invasive as a multiligament repair and/or reconstruction and thus still considered under the realm of “nonoperative” treatment options. An essential part of the procedure prior to fixator application should be an extensive examination of the joint and ligaments to document the extent and severity of the injury under anesthesia. 
Figure 56-23
 
External fixator placed to maintain knee joint reduction; note the pin placement anteromedial on the tibia and anterolateral on the femur.
External fixator placed to maintain knee joint reduction; note the pin placement anteromedial on the tibia and anterolateral on the femur.
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Figure 56-23
External fixator placed to maintain knee joint reduction; note the pin placement anteromedial on the tibia and anterolateral on the femur.
External fixator placed to maintain knee joint reduction; note the pin placement anteromedial on the tibia and anterolateral on the femur.
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A fixator is an essential adjunct in the treatment of knee dislocations complicated by vascular injury requiring a revascularization procedure.197 In this instance, the fixator is optimally applied just before performing the vascular bypass and allows for a stable construct so that the vessel repair can be performed—and heal—undisturbed by subluxation and instability episodes. 
There are times when a fixator can be helpful but not essential—particularly with extensive open wounds and compromise of the soft tissue envelope requiring multiple irrigation and debridement procedures.98,196,221 In the case of extensor mechanism disruption, a fixator will allow a period of “splinting” that will protect a quadriceps or patellar tendon repair prior to consideration of formal ligament reconstruction and/or repair.149,223 
We recommend against the routine application of external fixators after reduction of knee dislocations. Pin site infections are not uncommon and have the potential to colonize the soft tissue envelope around the joint—thereby putting planned subsequent ligament reconstruction procedures (especially those with allograft tissue) in jeopardy. Moreover, fixators are not easy to apply in the setting of a highly unstable joint and can significantly compromise the ability to restore quadriceps muscle bulk and function if left on too long. 
If required, an external fixator is placed across the reduced knee with pins in both the femur and the tibia. Care should be taken to position pins in extra-articular locations to avoid potential colonization of the joint. The surgeon should be aware of the proximal extent of the knee joint capsule and its reflections. Proximal pins are also optimally positioned so that they avoid the quadriceps mechanism. Distally, pins are best placed in the subcutaneous AM surface of the tibia so as to limit the potential for infection. Several pin/frame constructs, including articulated and hinged fixators, have been described. These have the advantage of allowing some early motion but are exceptionally difficult to apply.50,125 
Table 56-4 lists the indications and contraindications for nonoperative management of knee dislocations. Note that application of a fixator may be considered as an adjunct in situations of dysvascularity, extensive soft tissue compromise, compartment syndrome, and after reduction of irreducible dislocations. In all other situations—provided that the knee is concentrically reduced—immobilization in extension with a brace or cast is the preferred method of initial nonoperative management. 
Table 56-4
Indications and Relative Contraindications for Nonoperative Treatment of Knee Dislocations
Knee Dislocations
Nonoperative Treatment
Indications Relative Contraindications
Comorbidity and/or concomitant injury of sufficient severity to preclude extensive surgery and/or anesthetic. (relative) Open dislocationsa
Skeletal immaturity (relative) Dislocations with associated vascular injuryb
Irreducible dislocationsc
Dislocations with associated compartment syndromed
Dislocations with subsequent multiligament laxity and joint subluxation.
X

Operative Treatment of Knee Dislocations

Timing of surgery is controversial in the dislocated knee. A systematic review by Levy et al.116 reported improved outcomes for patients treated with early surgical intervention. Conversely, Mook et al.138 reported an increased rate of arthrofibrosis in patients undergoing early surgical intervention. The timing of surgery is also influenced by additional factors beyond the ligamentous injuries such as periarticular fractures, soft tissue injury, or other concomitant injuries. For the purposes of this chapter, we divide the timing of surgery into two categories: (1) emergent and (2) nonemergent. Nonemergent surgery will then be further subdivided into (1) early (1 to 3 weeks) or (2) delayed (greater than 3 weeks). We also provide specific sections on ligament repair, ligament reconstruction, and the indications for staged procedures. 

Emergent Intervention—Indications/Contraindications

Indications for emergent surgery include the dislocated knee with an arterial injury requiring repair, knee dislocation with associated compartment syndrome, open knee dislocation, and irreducible knee dislocation. In the setting of an arterial injury requiring repair, we typically apply a spanning external fixator just before having the vascular surgeons perform the vascular repair or bypass graft. This allows for a stable limb during the vascular procedure and protects the arterial repair thereafter. 
In the setting of a compartment syndrome, four compartment fasciotomies are emergently performed followed by an examination under anesthesia with fluoroscopic stress radiography. If the joint is able to be maintained in a reduced position, negative pressure wound therapy and a brace are applied. However, if the tibiofemoral articulation is unable to be maintained in a reduced position, a spanning external fixator is applied. 
Open knee dislocations require that all skin and tissue wounds undergo a thorough irrigation and debridement (I&D). A spanning external fixator is then applied to allow easy transportation of patients who will be having multiple subsequent I&D procedures. Oftentimes, skin grafts or muscle flaps are required and a team approach is therefore mandated with the help of plastic surgery colleagues. Open knee dislocations require a stable soft tissue envelope and without evidence of infection before proceeding with ligament reconstruction. 
The irreducible knee dislocation is uncommon but requires prompt recognition and intervention. Irreducible dislocations typically occur with a PL knee dislocation where the medial femoral condyle dislocates anterior to the tibia and is buttonholed through the medial retinaculum or MCL. Oftentimes, a puckering or dimpling of the medial soft tissues is noted.212 In this situation, an emergent arthrotomy is performed to release the entrapped medial femoral condyle from the surrounding structures and allow joint reduction. A straight midline arthrotomy is typically performed to achieve the best exposure and allow prompt reduction. 

Operative Considerations

Preoperative Planning.
Prompt recognition of an emergent limb-threatening injury is the first step in preoperative planning. Early discussion with the orthopedic trauma team, general surgery trauma team, and the vascular surgery team is imperative so that all surgical personnel are aware of the emergent situation and the surgical plan. In the case of a vascular injury requiring repair, the vascular surgeons will address all of their operative needs. From an orthopedic standpoint, we plan to have intraoperative fluoroscopy available and we have a spanning external fixation device in the room unopened, in case it is needed. 
For open knee dislocations, we have 9 to 12 L of normal saline with low-pressure pulsatile lavage available and make sure that a negative pressure wound therapy device is readily available. The extent of the bony injury as evaluated intraoperatively will ultimately determine which treatment is utilized. 
Surgical Techniques.
Patient positioning for any emergent surgical indication is generally supine, but specific situations may require alternative positions. For vascular injuries requiring repair, the injured limb is typically put in a slightly flexed and externally rotated position that allows the vascular surgeon to have access to the artery through a PM approach. Prior to the arterial repair, intraoperative fluoroscopy is used for a quick assessment of the knee with valgus and varus and posterior drawer stress views to define the ligament instability pattern. It is our preference to apply a fixator prior to vascular repair to stabilize the limb and protect the repair site. Once the vascular repair is complete, the limb may be fully extended in the fixator at the discretion of the orthopedic and vascular surgeons. 
When applying an external fixator, we typically place two or three Schanz pins in the AM tibial distal to where our tunnels will be placed later during reconstruction and then two or three Schanz pins in the AL femur within one-hand breadth of the proximal pole of the patella with the leg in full extension. It is essential to avoid placing them in the suprapatellar pouch and potentially contaminating the knee joint. 
In the case of compartment syndrome with a knee dislocation, our typical technique for fasciotomies is that as described by Mubarak and Owen142 using two 15-cm-long incisions on the medial and lateral sides of the lower leg with at least a 7-cm bridge between the two (Fig. 56-24). 
Figure 56-24
 
A: Lateral and (B) medial views of the limb with an external fixator in place and four-compartment fasciotomy incisions after knee dislocation; note the incision on the medial distal thigh for the popliteal artery repair.
A: Lateral and (B) medial views of the limb with an external fixator in place and four-compartment fasciotomy incisions after knee dislocation; note the incision on the medial distal thigh for the popliteal artery repair.
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Figure 56-24
A: Lateral and (B) medial views of the limb with an external fixator in place and four-compartment fasciotomy incisions after knee dislocation; note the incision on the medial distal thigh for the popliteal artery repair.
A: Lateral and (B) medial views of the limb with an external fixator in place and four-compartment fasciotomy incisions after knee dislocation; note the incision on the medial distal thigh for the popliteal artery repair.
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In the case of an irreducible knee dislocation, one can perform either a mid-line arthrotomy with large soft tissue flaps or a straight medial incision to directly approach the medial retinaculum through which the medial femoral condyle has perforated. At times, a combination of these approaches is necessary to reduce the knee. 
Postoperative Care.
If an external fixator is placed, it is imperative that the pin sites are cleaned on a daily basis. In addition, the patient should do straight leg raises as well as ankle pumps for rehabilitation while the external fixator is in place. 
In the setting of an open knee dislocation, patients are typically returned to the operating room at 48 hours for further debridement and irrigation as necessary to treat all open or degloving wounds about the knee. 
When fasciotomies are performed, our normal approach is to return the patient to surgery at 48-hour increments for further debridement as necessary. When possible, the wounds are closed, or if the wounds are not able to be closed, split-thickness skin grafts are used to obtain coverage. 
Following reduction of an irreducible knee dislocation, we will permit early range-of-motion exercises and then plan ligament reconstruction and/or repairs depending on the specific injury patterns as noted later. 
Potential Pitfalls and Preventive Measures.
When applying a spanning external fixator, one of the key pitfalls to avoid is improper placement of the Schanz pin sites. It is critical to avoid placing the distal femoral pin intra-articularly as doing so could damage the intra-articular structures and predispose the patient to intra-articular infection. In addition, the proximal tibial pin must not be placed too close to the anticipated tunnels or sockets for the ACL and PCL reconstructions. Following the instructions as noted later in the technique section will help prevent improper placement of these pin sites. 
In the case of an irreducible knee dislocation, even when the knee appears to be reduced, the extensive soft tissue injury may create gross tibiofemoral joint instability. Therefore, it is important to use fluoroscopy intraoperatively to ensure that the tibiofemoral joint is reduced and to assess instability to decide whether or not a spanning fixator will be necessary. 
Treatment-Specific Outcomes.
We have previously reported outcomes after the use of a spanning external fixator following our staged protocol.118 In this series, final functional outcomes were similar to those reported in patients who did not have spanning fixation. Also, Sems et al.180 reported on the safety of placing a spanning external fixator with regard to the development of deep venous thrombosis (DVT) and showed only a 2.1% DVT risk with the use of lower extremity spanning fixators following trauma, a rate similar to a published rate for DVT in a setting without spanning fixation. 
Open knee dislocations are uncommon injuries and there is little in the literature on outcomes after this injury. In 1995, Wright et al.221 reported on 19 open knee dislocations in 18 patients. Only 14 knees were able to be salvaged as 3 required above-knee amputation, 1 required arthrodesis, and 1 required a total knee arthroplasty. All 14 salvaged knees had poor or fair functional outcomes as measured with the Hospital for Special Surgery Knee Injury Score. More recently, King et al.98 performed a retrospective review of outcomes after traumatic open knee dislocation in seven patients treated with ligament reconstruction after limb salvage procedures were completed. These patients underwent an average of 10.7 surgical procedures including an average of 6.6 I&Ds. Even with the extensive and aggressive management, three patients still developed an infection with 1 patient requiring an amputation secondary to the infection. Only two of the seven patients had good or excellent results and six reported residual symptoms or function deficits. 
Irreducible knee dislocations are quite rare, and as such, there is very little in the literature regarding outcomes. Case reports have reported success in allowing good ambulation and return to work for patients treated emergently for irreducible knee dislocations,34,84,146,184 but no large series have been published. 

Nonemergent Intervention—Indications/Contraindications

Early Repair.
Repair versus reconstruction remains a controversial topic. Previously, many surgeons advocated early repair of injured structures before scarring of the soft tissues occurred. Other authors advocated lateral-sided repair, but waiting until scar tissue formed then releasing the scar tissue “en mass” and advancing and reattaching it with screw fixation.182 Levy et al.116 performed a systematic review of the management of knee dislocations and reported a higher rate of failure for repair of lateral-sided structures and repair of the cruciate ligaments resulted in decreased stability and range of motion, and lower return to preinjury activity levels compared with reconstruction. Several authors have noted high failure rates with early repair of the lateral side. Stannard et al.189 reported a prospective nonrandomized trial comparing 57 patients with minimum 2-year follow-up. The failure rate in the repair group was 37% and the failure rate in the reconstruction group was only 9%. Subsequently, Levy et al.115 compared repair versus reconstruction of the lateral-sided structures with minimal 2-year follow-up in 28 patients and found a failure rate of 40% in the repair group and 6% in the reconstruction group. These 2 studies were very similar with regard to failure rates, and most authors now agree that repair alone of lateral and PLC structures in the acute setting is not ideal. 
For the medial and PMC structures, a systematic review of operative management of medial sided-injuries showed satisfactory results with both repair and reconstruction of the MCL, but no studies directly compared repair with reconstruction.100 To our knowledge, there is only 1 published study comparing the results of repair versus reconstruction. Stannard et al.188 reported their results in 73 dislocated knees with medial-sided injuries with a mean follow-up of 43 months. They had 25 patients in their repair group, 27 in an autograft reconstruction group, and 21 in an allograft reconstruction group. The failure rate for the repair group was 20% compared with 4% in the reconstruction groups combined. 

Indications/Contraindications

Early Reconstruction (± Repair).
If there are no emergent indications for surgery, it is recommended that patients undergo early surgical intervention.120 This affords both the surgeon and patient time to monitor the vascular status, allow reduction of any swelling, obtain advanced imaging, plan the optimal surgical procedures, procure the necessary equipment and grafts, and assemble an experienced team. Indications for acute surgery include (1) an extensive medial-sided disruption and (2) a flipped or displaced meniscal tear preventing range of motion. 
In the setting of a flipped meniscus, it is often not possible to perform preoperative range-of-motion exercises. Therefore, a displaced meniscus tear, although not an emergent situation, typically represents an acute situation that needs to be addressed surgically. The surgeon, through either an open or arthroscopic approach, should repair the meniscus and then protect the knee with either a brace or spanning fixator. Once the meniscus has healed, the patient will then return for a second-stage ligament repair and/or reconstruction. 
Extensive medial-sided disruption will often involve meniscocapsular separations and complete tears of the MCL and PMC structures distally. Fanelli et al.42,43 showed improved outcomes when these extensive medial-sided disruptions were treated and repaired within 10 to 14 days with simultaneous reconstruction of the MCL. 

Staged Approaches

Indications/Contraindications

Several authors39,75 have noted decreased morbidity in periarticular fracture care with so-called “staged protocols.” We have, therefore, utilized a staged protocol for the acutely dislocated knee in a similar fashion. Stage 1 consists of an examination under anesthesia with the selected use of spanning external fixation followed by MRI and DVT prophylaxis. Stage 2 is ligamentous repair and/or reconstruction when the soft tissues allow, typically at 2 to 6 weeks postinjury. The reasons for using spanning external fixation are (1) to protect a vascular repair, (2) to stabilize and allow dressing changes and repeated debridements of an open dislocation, and (3) to maintain joint reduction when gross instability is present. In a study by Levy et al.,118 patients treated with a staged protocol and spanning external fixation showed no difference in final functional outcomes compared with patients who did not have a spanning external fixator, although those with a fixator did have a higher rate of arthrofibrosis. 

Delayed Reconstruction

Indications/Contraindications

Surgical intervention is typically delayed beyond 3 weeks in the setting of unacceptable skin condition or swelling, vascular repair, or associated injuries that preclude the ability to perform ligament reconstruction such as tibial plateau fractures or femoral fractures requiring internal fixation (Fig. 56-25). Another indication for delayed surgery is combined ACL, PCL, and MCL disruptions where the MCL is avulsed from its femoral attachment (Fig. 56-26). This particular MCL injury has a very high likelihood of healing within 6 to 8 weeks, at which point the surgeon can then perform ACL and PCL reconstructions, avoiding MCL surgery altogether. The advantages of delayed surgery include those of acute surgery in addition to promoting wound healing, securing additional time for swelling reduction, having the ability to monitor vascular repair status, treating associated injuries, and beginning a controlled rehabilitation program using a brace to control range of motion while maintaining joint reduction prior to ligament reconstruction. 
Figure 56-25
 
A: AP radiograph of a knee dislocation with a proximal tibial plateau fracture, a fibular fracture, and a proximal tibiofibular joint disruption requiring. B: Acute open reduction and internal fixation and delayed reconstruction of the dislocation
 
(From Levy BA, Stuart MJ. ACL, PCL, and medial-sided injuries of the knee. In: Fanelli GC, ed. The Multiple Ligament Injured Knee: A Practical Guide to Management. New York: Springer; 2012, with permission).
A: AP radiograph of a knee dislocation with a proximal tibial plateau fracture, a fibular fracture, and a proximal tibiofibular joint disruption requiring. B: Acute open reduction and internal fixation and delayed reconstruction of the dislocation
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Figure 56-25
A: AP radiograph of a knee dislocation with a proximal tibial plateau fracture, a fibular fracture, and a proximal tibiofibular joint disruption requiring. B: Acute open reduction and internal fixation and delayed reconstruction of the dislocation
(From Levy BA, Stuart MJ. ACL, PCL, and medial-sided injuries of the knee. In: Fanelli GC, ed. The Multiple Ligament Injured Knee: A Practical Guide to Management. New York: Springer; 2012, with permission).
A: AP radiograph of a knee dislocation with a proximal tibial plateau fracture, a fibular fracture, and a proximal tibiofibular joint disruption requiring. B: Acute open reduction and internal fixation and delayed reconstruction of the dislocation
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Figure 56-26
 
Coronal T2 MRI scan showing an MCL avulsion from its femoral attachment; note the medial joint space widening.
Coronal T2 MRI scan showing an MCL avulsion from its femoral attachment; note the medial joint space widening.
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Figure 56-26
Coronal T2 MRI scan showing an MCL avulsion from its femoral attachment; note the medial joint space widening.
Coronal T2 MRI scan showing an MCL avulsion from its femoral attachment; note the medial joint space widening.
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Operative Considerations of Knee Dislocations

Preoperative Planning

After obtaining appropriate diagnostic imaging, which typically includes plain radiographs, MRI, and stress views, the surgeon can begin preoperative planning. As noted previously, the timing of surgery is dependent on a multitude of factors of which the surgeon must be aware. Once the decision of repair and/or reconstruction has been made on the basis of the ligaments injured and their zones of injury, the surgeon may start developing the operative plan. Factors that must be considered during preoperative planning include the type of grafts and fixation to be used, tunnel, and/or socket position and size, and all equipment and implants needed. Because of the complexity of multiligament reconstruction, it is very valuable to template the tunnels and/or sockets. Using plain radiographs with digital scanning, the tunnel positions or socket positions for the ligaments are drawn out as an operative template, noting the size of the tunnels and/or sockets and the size of the screws needed (Fig. 56-27). All necessary grafts, implants, and equipment are recorded, as is the order of the surgical intervention. Thorough preoperative planning is absolutely critical to maintain a safe and efficient environment for the patient. 
Figure 56-27
 
Anteroposterior (AP) radiograph with digital scanning showing planned tunnel placements for multiligament reconstruction.
Anteroposterior (AP) radiograph with digital scanning showing planned tunnel placements for multiligament reconstruction.
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Figure 56-27
Anteroposterior (AP) radiograph with digital scanning showing planned tunnel placements for multiligament reconstruction.
Anteroposterior (AP) radiograph with digital scanning showing planned tunnel placements for multiligament reconstruction.
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Positioning

Positioning of the patient in the operating room is somewhat surgeon-dependent. Some surgeons recommend starting with the patient positioned supine with both limbs flat. In other words, if you were operating on a left lower extremity, the right leg would be lying flat on the operating table and the left leg would be positioned in a holder to be able to extend and flex the knee. Other surgeons position the patient so that both legs hang over the edge of the table in an abducted position. This allows fluoroscopy to enter easily from either side and allows the surgeon to perform the central pivot reconstruction in a standard fashion using an arthroscopic leg holder. The disadvantage of having the contralateral limb in a dependent position for several hours is the risk of compartment syndrome of that lower extremity. By having the leg flat on the table, one can avoid this complication. If the central pivot portion of the operation is performed with the legs hanging over the table edge, then the patient must be repositioned before performing the medial and lateral-sided reconstructions. 
Fanelli et al.42,46 have popularized a technique in which the contralateral limb is lying flat on the operating table and the operated limb hangs over the edge of the table at 90°. The surgeon sits on a stool with a gown covering the surgeon’s legs down to his or her feet and the foot of the operated limb resting on the surgeon’s lap. Once the central pivots are reconstructed, the operated leg is placed back flat on the operating table and medial and lateral-sided reconstructions are performed as indicated. 

Surgical Approach/Technique

The first step in all cases is a thorough physical examination under anesthesia. We typically perform bilateral physical examination of both knees to get a good sense of the true ligament instability pattern. A complete ligamentous examination of the contralateral knee is critical as patients have variable degrees of generalized laxity. Therefore, ligamentous instability can only really be assessed after having a full understanding of what the patient’s normal knee laxity is. Once the physical examination is complete, we objectively document the amount of laxity with bilateral fluoroscopic stress views. We perform varus and valgus stress tests, as well as anterior and posterior drawer tests of both knees. This allows us not only to confirm our physical examination findings but to objectively document the amount of laxity with side-to-side comparison. 
The next step is to position the patient as noted previously for the surgical procedure and apply a tourniquet, although it is rarely inflated. The leg is then prepared and draped, and the image intensifier is draped as well. Before commencing the surgical procedure, the entire surgical team, including the surgeons, nursing staff, circulating nurse, and anesthesia team, gathers to discuss the steps of the operation, the expected timing of the operation, and all the potential complications. This will ensure an efficient and safe surgical intervention. We also recommend that the fluoroscopy technicians perform trial AP and lateral views so they are properly positioned to avoid any delays during the surgical procedure. 
After the patient is positioned and the surgical team briefing is complete, the next step is preparing the grafts as necessary. Some surgeons will prepare all the grafts before the patient even enters the room, while other surgeons, if they have a large enough team, will begin the surgical procedure while members of their team prepare the grafts. This can be done only in the setting of allograft reconstructions; otherwise, autografts are typically harvested at the beginning of the operation prior to the ligament surgery. Graft preparation is performed as per surgeon preference and all of the grafts are labeled and marked in separate containers. 
A diagnostic arthroscopy is first performed in all cases to identify any loose bodies and chondral surface or meniscal injury and treat them as indicated. Arthroscopically, we assess the ACL and PCL as well as the popliteus tendon, which is easily identified at its femoral attachment site. Special attention is paid to any medial or lateral joint space widening with the so-called “drive through” signs. Once the diagnostic arthroscopy has been completed, we focus our attention on ligament repair or reconstruction as indicated. 

Ligament Repair Related to Knee Dislocations

FCL/PLC Repair

Lateral-sided repairs are approached through a lateral incision regardless of location of injury. A 6-cm incision starts just at the midway portion of the fibular head/neck junction and is brought about 2 cm proximal to the lateral epicondyle. Dissection is carried down to the IT band and then the three window incisions as described by Terry and LaPrade204 are performed. Window 1 is in the midsubstance of the IT band starting just proximal to the epicondyle and extending to Gerdy’s tubercle. Window 2 is the soft tissue plane between the posterior border of the IT band and the anterior border of the biceps femoris tendon. Window 3 is the soft tissue window posterior to the biceps femoris where the peroneal nerve is located. 
Once the windows are created, the peroneal nerve is dissected free, protected with a vessel loop, and traced proximally and distally. This allows complete protection of the nerve throughout the procedure. Through these windows, there are several anatomical structures that need to be identified, including the FCL, the biceps femoris tendon, the popliteal fibular ligament, the popliteus tendon, the PL capsule, and the lateral head of the gastrocnemius. One of the tricks to finding the FCL fibular attachment site is to make a little slit in the biceps bursa. It lies just proximal to the fibular head where the biceps tendon attaches. If you expose this region, you can find the distal attachment of the FCL and pull on it, which will help direct your proximal dissection as well. 
In most distal avulsions, the PL capsule is detached from the tibia, the FCL and biceps are detached from the fibula, and at times, the popliteus tendon is detached from the femur. In addition, the popliteus sometimes has a musculotendinous junction tear. Once all these structures have been identified, locking whip stitches are placed in the FCL and the biceps tendon and passed through drill holes in the fibular head and the FCL and the biceps tendon are reattached to the bone as described by Geeslin and LaPrade59,60 (Fig. 56-28). In the case of poor-quality tissue, we may use a bidirectional repair augmenting the sutures through drill holes in the bone with suture anchors for bidirectional support. 
Figure 56-28
 
A: Lateral radiograph showing a fibular head avulsion fracture in the setting of knee dislocation; (B) photograph depicting suture fixation of an avulsed fibular head fracture. (From Levy BA, Stuart MJ. Treatment of PCL, ACL, and lateral-side knee injuries: acute and chronic. J Knee Surg. 2012;25(4):295–305, with permission).
A: Lateral radiograph showing a fibular head avulsion fracture in the setting of knee dislocation; (B) photograph depicting suture fixation of an avulsed fibular head fracture. (From Levy BA, Stuart MJ. Treatment of PCL, ACL, and lateral-side knee injuries: acute and chronic. J Knee Surg. 2012;25(4):295–305, with permission).
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Figure 56-28
A: Lateral radiograph showing a fibular head avulsion fracture in the setting of knee dislocation; (B) photograph depicting suture fixation of an avulsed fibular head fracture. (From Levy BA, Stuart MJ. Treatment of PCL, ACL, and lateral-side knee injuries: acute and chronic. J Knee Surg. 2012;25(4):295–305, with permission).
A: Lateral radiograph showing a fibular head avulsion fracture in the setting of knee dislocation; (B) photograph depicting suture fixation of an avulsed fibular head fracture. (From Levy BA, Stuart MJ. Treatment of PCL, ACL, and lateral-side knee injuries: acute and chronic. J Knee Surg. 2012;25(4):295–305, with permission).
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Fibular head fractures are often associated with peroneal nerve injury and necessitate early intervention. In the case of a fibular head fracture, the same exposures are performed. The fibular head is reduced with a reduction clamp, and then a long 100 mm × 3.5 mm or 4.5-mm flexible titanium screw is used for fixation (Fig. 56-29). In the case of a proximal disruption of the FCL and popliteus tendon, our results have shown very poor outcomes with repair alone. Therefore, in those settings we will identify the attachment sites of the FCL and the popliteus tendon and reattach them with suture anchors and augment the repaired tissues with a reconstruction using either autograft or allograft tissue as described later for our routine PLC and FCL reconstruction technique (Fig. 56-30). 
Figure 56-29
 
Anteroposterior (AP) radiographs of (A) a fibular head avulsion fracture and (B) open reduction and internal fixation of the fibular head fracture with a 3.5-mm screw (From Levy BA, Stuart MJ. Treatment of PCL, ACL, and lateral-side knee injuries: acute and chronic. J Knee Surg. 2012;25(4):295–305, with permission).
Anteroposterior (AP) radiographs of (A) a fibular head avulsion fracture and (B) open reduction and internal fixation of the fibular head fracture with a 3.5-mm screw (From Levy BA, Stuart MJ. Treatment of PCL, ACL, and lateral-side knee injuries: acute and chronic. J Knee Surg. 2012;25(4):295–305, with permission).
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Figure 56-29
Anteroposterior (AP) radiographs of (A) a fibular head avulsion fracture and (B) open reduction and internal fixation of the fibular head fracture with a 3.5-mm screw (From Levy BA, Stuart MJ. Treatment of PCL, ACL, and lateral-side knee injuries: acute and chronic. J Knee Surg. 2012;25(4):295–305, with permission).
Anteroposterior (AP) radiographs of (A) a fibular head avulsion fracture and (B) open reduction and internal fixation of the fibular head fracture with a 3.5-mm screw (From Levy BA, Stuart MJ. Treatment of PCL, ACL, and lateral-side knee injuries: acute and chronic. J Knee Surg. 2012;25(4):295–305, with permission).
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Figure 56-30
 
Intraoperative photographs of A: a native FCL repair with B: augmentation of the repair with a gracilis tendon autograft.
Intraoperative photographs of A: a native FCL repair with B: augmentation of the repair with a gracilis tendon autograft.
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Figure 56-30
Intraoperative photographs of A: a native FCL repair with B: augmentation of the repair with a gracilis tendon autograft.
Intraoperative photographs of A: a native FCL repair with B: augmentation of the repair with a gracilis tendon autograft.
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Midsubstance injuries have also done poorly with repair alone as demonstrated by Levy et al.115 and Stannard et al.189 Therefore, in this case, we again prefer not to repair the tissue but perform a reconstruction technique. 

MCL/PMC Repair

For medial-sided injuries, exposure of the MCL femoral attachment sites on the medial side of the knee can be performed either through a midline approach to the knee or, more commonly, through a separate medial incision. A 4-cm incision is carried down to the crural fascial layer and then under fluoroscopic control, on a true lateral view of the knee the isometric point and superficial MCL femoral attachment site is identified according to the method of Wijdicks et al.219 with a 2.4-mm K-wire (Fig. 56-31). This will help guide the rest of the dissection, which will be essentially full thickness down to the MCL. In the acute setting where the anatomical layers are readily identifiable, it is important to identify key anatomic structures including the semimembranosus tendon attaching at the proximal tibia; the adductor magnus, which has a very discrete tendinous and bony protuberance; and the medial head of the gastrocnemius. These are all PM structures, which can make the medial epicondyle sometimes very difficult to palpate. For this reason, we use fluoroscopic guidance to help identify the superficial MCL attachment site. Once this is achieved and the MCL is identified, a 3.2-mm drill is inserted at the MCL anatomic insertion to a depth of approximately 35 to 40 mm. The MCL is prepared with a suture post/spiked ligament washer construct where a modified running locking stitch is placed and woven up and down both sides of the proximal attachment of the MCL. A small slit is made in the proximal fibers and then a 4.5-mm screw with a soft tissue spiked washer is placed through the slit in the MCL into the predrilled region and secured. The sutures extend proximally and actually act as a post so one can achieve dual fixation with the screw/washer construct. The first fixation is the soft tissue washer and the second is the sutures around the post (Fig. 56-32). 
Figure 56-31
Illustration (left) and fluoroscopic view (right) of the femoral osseous insertion sites for the medial side structures of the knee.
 
Line 1 is a distal extension of the posterior femoral cortex. Line 2 runs perpendicular to line 1 from the posterior aspect of Blumensat’s line. Point “E” corresponds to the femoral attachment of the superficial MCL and lies just anterior (with the knee extended) to the intersection of line 1 and Blumensat’s line. (From Wijdicks CA, Griffith CJ, LaPrade RF, et al. Radiographic identification of the primary medial knee structures. J Bone Joint Surg Am Vol. 2009 Mar 1;91(3):521–529, with permission).
Line 1 is a distal extension of the posterior femoral cortex. Line 2 runs perpendicular to line 1 from the posterior aspect of Blumensat’s line. Point “E” corresponds to the femoral attachment of the superficial MCL and lies just anterior (with the knee extended) to the intersection of line 1 and Blumensat’s line. (From Wijdicks CA, Griffith CJ, LaPrade RF, et al. Radiographic identification of the primary medial knee structures. J Bone Joint Surg Am Vol. 2009 Mar 1;91(3):521–529, with permission).
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Figure 56-31
Illustration (left) and fluoroscopic view (right) of the femoral osseous insertion sites for the medial side structures of the knee.
Line 1 is a distal extension of the posterior femoral cortex. Line 2 runs perpendicular to line 1 from the posterior aspect of Blumensat’s line. Point “E” corresponds to the femoral attachment of the superficial MCL and lies just anterior (with the knee extended) to the intersection of line 1 and Blumensat’s line. (From Wijdicks CA, Griffith CJ, LaPrade RF, et al. Radiographic identification of the primary medial knee structures. J Bone Joint Surg Am Vol. 2009 Mar 1;91(3):521–529, with permission).
Line 1 is a distal extension of the posterior femoral cortex. Line 2 runs perpendicular to line 1 from the posterior aspect of Blumensat’s line. Point “E” corresponds to the femoral attachment of the superficial MCL and lies just anterior (with the knee extended) to the intersection of line 1 and Blumensat’s line. (From Wijdicks CA, Griffith CJ, LaPrade RF, et al. Radiographic identification of the primary medial knee structures. J Bone Joint Surg Am Vol. 2009 Mar 1;91(3):521–529, with permission).
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Figure 56-32
An MCL repair using the suture post and ligament washer construct
 
(From Levy BA, Stuart MJ. ACL, PCL, and medial-sided injuries of the knee. In: Fanelli GC, ed. The Multiple Ligament Injured Knee: A Practical Guide to Management. New York: Springer; 2012, with permission).
(From Levy BA, Stuart MJ. ACL, PCL, and medial-sided injuries of the knee. In: Fanelli GC, ed. The Multiple Ligament Injured Knee: A Practical Guide to Management. New York: Springer; 2012, with permission).
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Figure 56-32
An MCL repair using the suture post and ligament washer construct
(From Levy BA, Stuart MJ. ACL, PCL, and medial-sided injuries of the knee. In: Fanelli GC, ed. The Multiple Ligament Injured Knee: A Practical Guide to Management. New York: Springer; 2012, with permission).
(From Levy BA, Stuart MJ. ACL, PCL, and medial-sided injuries of the knee. In: Fanelli GC, ed. The Multiple Ligament Injured Knee: A Practical Guide to Management. New York: Springer; 2012, with permission).
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Distal MCL avulsions can be easily approached through a 4-cm AM incision midway between the PM border of the tibia and the tibial tubercle. Dissection is carried down to the sartorius expansion and the expansion is incised over the top of the pes tendons. The pes tendons are identified and retracted distally, and the superficial MCL will be found just deep to the pes tendons in this area. Most distal avulsions will occur below the level of the pes tendons, and sometimes the superficial MCL is retracted a significant distance proximally. Our first step is to place two suture anchors at the level of the superficial MCL attachment site in the proximal tibia, about 1 cm below the joint line, and then we weave those sutures through the proximal MCL fibers. Then, similar to the proximal MCL attachment, the distal MCL is identified and locking whip stitches are run along the anterior and posterior borders. A slit is made in the ligament. Using a 3.2-mm drill, a pilot hole is drilled and then a 4.5-mm bicortical spiked washer and screw construct are placed. The suture is then wrapped around the post prior to final tensioning, which is performed with the leg in about 20° to 30° degrees of flexion and slight varus. Once the distal avulsion has been repaired, the leg is placed in full extension and the proximal anchors are then sutured securely. 
The so-called “Stener” lesion of the knee occurs when the superficial MCL fibers are torn from their distal attachment and then flip up and over the gracilis and semitendinosus hamstring tendons. In this situation, there is very little chance for the MCL to heal back to the bone as it overlies the tendons. In this situation, acute repair of the distal MCL is performed and then central pivot and lateral-sided injuries are treated in a second stage (Fig. 56-33). In rare instances, high-energy knee dislocations may result in the “ultimate Stener lesion” wherein the avulsed distal MCL is actually trapped underneath a medial tibial plateau rim fracture (Fig. 56-34). In this case, the MCL should be removed from the entrapping bony fragment and repaired to its distal attachment and the fracture treated by open reduction and internal fixation. 
Figure 56-33
 
A: Coronal MRI showing distal “Stener-like lesion” of the MCL; (B) clinical photograph depicting distal MCL avulsion repair. Note that the pes tendons are now superficial to the MCL tibial attachment.
A: Coronal MRI showing distal “Stener-like lesion” of the MCL; (B) clinical photograph depicting distal MCL avulsion repair. Note that the pes tendons are now superficial to the MCL tibial attachment.
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Figure 56-33
A: Coronal MRI showing distal “Stener-like lesion” of the MCL; (B) clinical photograph depicting distal MCL avulsion repair. Note that the pes tendons are now superficial to the MCL tibial attachment.
A: Coronal MRI showing distal “Stener-like lesion” of the MCL; (B) clinical photograph depicting distal MCL avulsion repair. Note that the pes tendons are now superficial to the MCL tibial attachment.
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Figure 56-34
 
A: Coronal T2 magnetic resonance image of the “Ultimate Stener-like lesion” with the superficial MCL trapped underneath a medial tibial plateau rim fracture and (B) fluoroscopic view of ORIF and MCL repair (From Levy BA, Stuart MJ. ACL, PCL, and medial-sided injuries of the knee. In: Fanelli GC, ed. The Multiple Ligament Injured Knee: A Practical Guide to Management. New York: Springer; 2012, with permission).
A: Coronal T2 magnetic resonance image of the “Ultimate Stener-like lesion” with the superficial MCL trapped underneath a medial tibial plateau rim fracture and (B) fluoroscopic view of ORIF and MCL repair (From Levy BA, Stuart MJ. ACL, PCL, and medial-sided injuries of the knee. In: Fanelli GC, ed. The Multiple Ligament Injured Knee: A Practical Guide to Management. New York: Springer; 2012, with permission).
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Figure 56-34
A: Coronal T2 magnetic resonance image of the “Ultimate Stener-like lesion” with the superficial MCL trapped underneath a medial tibial plateau rim fracture and (B) fluoroscopic view of ORIF and MCL repair (From Levy BA, Stuart MJ. ACL, PCL, and medial-sided injuries of the knee. In: Fanelli GC, ed. The Multiple Ligament Injured Knee: A Practical Guide to Management. New York: Springer; 2012, with permission).
A: Coronal T2 magnetic resonance image of the “Ultimate Stener-like lesion” with the superficial MCL trapped underneath a medial tibial plateau rim fracture and (B) fluoroscopic view of ORIF and MCL repair (From Levy BA, Stuart MJ. ACL, PCL, and medial-sided injuries of the knee. In: Fanelli GC, ed. The Multiple Ligament Injured Knee: A Practical Guide to Management. New York: Springer; 2012, with permission).
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In the setting of PM capsular disruption or disruption of the posterior oblique ligament, horizontal mattress sutures are placed in the capsular tissue and, with the knee in full extension, tied down to the MCL to secure the PMC. 

Ligament Reconstruction Related to Knee Dislocations

When ligament reconstruction is indicated, we recommend starting with central pivot reconstruction. Using the arthroscope, the ACL tibial and femoral attachment sites should be debrided of any tissue remnants, with care being taken to make sure that the anatomic footprints are identified. Using a PM portal, the femoral and tibial attachment sites of the PCL are also cleared of all soft tissue debris and the centers of the anatomic footprints are identified. 

ACL Reconstruction

There are many considerations when performing ACL reconstruction including single- or double-bundle techniques, whether to use autograft or allograft, and the method of graft fixation. In the setting of a multiligament knee injury, both autograft and allograft tissue have demonstrated satisfactory clinical outcomes. The use of allograft has the advantages of choosing ideal graft size and eliminating donor site morbidity. There is considerable controversy regarding the use of single- or double-bundle reconstruction. While there may be some biomechanical benefit to double-bundle ACL reconstructions in regard to stability,99 no clinical studies have shown an advantage of one technique over the other.92,99,152 In the setting of multiligament knee reconstruction, however, the double-bundle ACL technique is contraindicated because other associated ligament reconstructions require socket and tunnel placements that may coalesce with the extra ACL sockets/tunnels. Our preferred technique for ACL reconstruction in the setting of multiligament surgery is a single-bundle soft tissue allograft with suspensory fixation on the femoral side and interference screw fixation on the tibial side with secondary backup. Alternatively, a patellar tendon allograft with femoral and tibial side interference screw fixation is also an excellent technique. More novel “all-inside” techniques, using a quadruple-looped, soft tissue allograft with suspensory fixation on both the tibial and femoral sides, have been developed, but we are unaware of any clinical data supporting their use. The advantage of these “all inside” techniques is that sockets are utilized as opposed to full bony tunnels, which minimizes the risk of interfering with other (PCL, FCL, and PLC) reconstructions. 
Arthroscopically, the femoral and tibial footprints are identified and the center of the femoral footprint is premarked with a 30° degree microfracture awl, and the tibial side is premarked with a radiofrequency device. Our preferred technique for femoral socket drilling is via a low AM portal using a hyperflexion technique. A spade-tip blade guide pin is positioned with the knee in hyperflexion. The osseous length that is typically between 35 and 45 mm is measured. Then, depending on the size of the graft, we use a low-profile reamer and ream the socket to a depth of approximately 25 mm. We then pass a suture for graft passage purposes and dock it through an accessory portal. For the tibial side, we use a standard tibial aiming guide at 55° to 60° and drill the tunnel retrograde with a 3.5-mm FlipCutter (Arthrex, Inc., Naples, Florida), although various sizes are available to use depending on the graft diameter. We then pass a suture for graft passage purposes through the tibia and dock it through a separate accessory portal. We then bring the graft construct through the tibial tunnel, first passing the femoral side sutures and flipping the tightrope button on the femur. We bring the graft up to a depth of 20 to 25 mm. The knee is then cycled to remove any creep in the system. We then secure the tibial side with a line-to-line bioabsorbable or BioComposite (Arthrex, Inc.) interference screw and back this up with a 5.5-mm SwivelLock (Arthrex, Inc.). Finally, the graft is assessed for stability. 

PCL Reconstruction

Similar to the ACL, there are numerous methods of PCL reconstruction including single- and double-bundle techniques, transtibial and tibial inlay, and allograft versus autograft. While successful outcomes have been shown for each of the different methods, the ideal technique remains controversial without a clear advantage to any particular technique.119 As with the ACL, in the setting of multiligament knee surgery, our preferred technique is a single-bundle allograft transtibial reconstruction. This technique, using Achilles tendon allograft, has demonstrated excellent long-term clinical outcomes.42 The first step in graft preparation is to create an 11-mm-thick by 28-mm-long bone block. A 2.4-mm guide pin is used to make holes in the bone block and #2 FiberWire (Arthrex, Inc.) sutures are placed through the holes for graft passage purposes. The soft tissue portion of the grafts typically extends 12 to 13 cm from the edge of the bone block and is tubularized using #2 FiberLoop (Arthrex, Inc.). The FiberLoop typically starts at 6 cm from the end of the graft and helps secure interference fixation (Fig. 56-35). 
Figure 56-35
PCL graft from Achilles tendon allograft
 
(From Levy BA, Kuzma SA, Krych AJ. Current concepts of posterior cruciate ligament reconstruction. Minerva Ortoped E Traumatol. 2012;63(5):345–363, with permission).
(From Levy BA, Kuzma SA, Krych AJ. Current concepts of posterior cruciate ligament reconstruction. Minerva Ortoped E Traumatol. 2012;63(5):345–363, with permission).
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Figure 56-35
PCL graft from Achilles tendon allograft
(From Levy BA, Kuzma SA, Krych AJ. Current concepts of posterior cruciate ligament reconstruction. Minerva Ortoped E Traumatol. 2012;63(5):345–363, with permission).
(From Levy BA, Kuzma SA, Krych AJ. Current concepts of posterior cruciate ligament reconstruction. Minerva Ortoped E Traumatol. 2012;63(5):345–363, with permission).
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Arthroscopically, the tibial and femoral PCL footprints are identified. For the tibial side, a PM portal is established to help remove all soft tissue from the base of the PCL facet. Oftentimes, a 70º arthroscope is utilized to aid in this step. It is critical to identify the most distal aspect of the PCL facet to ensure anatomic tunnel location. We then use the anatomic contoured PCL guide to hook the bottom of the PCL facet and set the guide to 60º to 65º off the tibial crest (Fig. 56-36). We then use an 11-mm FlipCutter and ream the tunnel in a retrograde fashion. On the femoral side, we identify the center of the AL bundle footprint. We drill the femoral side, using an inside-out technique, as we feel that this is safer with less risk of damaging the articular cartilage as the drilling can be directly visualized. We drill a Beath pin through the femur and, using a low-profile reamer, drill inside-out through the low accessory AL portal to create the femoral tunnel. An accessory superomedial incision with a subvastus approach to the femur is performed to access the femoral tunnel. The graft is then passed from the femoral side down out the tibial tunnel. The femoral side is secured with interference screw fixation and the knee is repetitively cycled to remove any creep from the system. We then place a Graft Tensioning Boot (Biomet, Warsaw, IN) on the leg to aid in graft tensioning and secure the PCL graft sutures. The knee is then flexed to 90º and the tibial side is secured with interference screw fixation backed up with a 5.5-mm SwiveLock. 
Figure 56-36
 
Fluoroscopic views of PCL anatomic contour guide: note the position of the guide pin at the most inferior aspect of the PCL facet between the mamillary bodies.
Fluoroscopic views of PCL anatomic contour guide: note the position of the guide pin at the most inferior aspect of the PCL facet between the mamillary bodies.
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Figure 56-36
Fluoroscopic views of PCL anatomic contour guide: note the position of the guide pin at the most inferior aspect of the PCL facet between the mamillary bodies.
Fluoroscopic views of PCL anatomic contour guide: note the position of the guide pin at the most inferior aspect of the PCL facet between the mamillary bodies.
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One important point when dealing with ACL and PCL reconstructions is the timing of fixation and graft tunnel/socket preparation. We typically prepare all the tunnels for the ACL and PCL reconstructions on both the femoral and tibial sides prior to graft passage and fixation (Fig. 56-37). We pass the PCL graft first and secure it to the femur, but not to the tibia. Similarly with the ACL, we will pass the ACL graft and secure it to the femur but not to the tibia. To fix the grafts on the tibia, we “set” the knee in full extension, pull tension on both the ACL and PCL tibial sides of the grafts, then flex the knee to 90º, and secure the PCL onto the tibia. We then put the leg back into full extension and secure the ACL graft. Once the ACL and PCL grafts are secured, we move on to lateral- and medial-sided repairs and/or reconstructions as indicated. 
Figure 56-37
Intraoperative fluoroscopic views showing (A) lateral view and (B) AP view of tibial PCL tunnel placement
 
(From Levy BA, Fanelli GC, Whelan DB, Stannard JP, MacDonald PA, Boyd JL, et al. Controversies in the treatment of knee dislocations and multiligament reconstruction. J Am Acad Orthopaed Surg. 2009;17(4):197–206, with permission).
(From Levy BA, Fanelli GC, Whelan DB, Stannard JP, MacDonald PA, Boyd JL, et al. Controversies in the treatment of knee dislocations and multiligament reconstruction. J Am Acad Orthopaed Surg. 2009;17(4):197–206, with permission).
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Figure 56-37
Intraoperative fluoroscopic views showing (A) lateral view and (B) AP view of tibial PCL tunnel placement
(From Levy BA, Fanelli GC, Whelan DB, Stannard JP, MacDonald PA, Boyd JL, et al. Controversies in the treatment of knee dislocations and multiligament reconstruction. J Am Acad Orthopaed Surg. 2009;17(4):197–206, with permission).
(From Levy BA, Fanelli GC, Whelan DB, Stannard JP, MacDonald PA, Boyd JL, et al. Controversies in the treatment of knee dislocations and multiligament reconstruction. J Am Acad Orthopaed Surg. 2009;17(4):197–206, with permission).
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As with ACL reconstruction, novel “all-inside” PCL reconstructions have been developed with the advantages of sockets as opposed to full tunnels. This may significantly reduce not only tunnel convergence with other ligament reconstructions in a primary case, but also the risk of tunnel widening and the need for bone grafting in revision cases. Currently, however, there are no clinical data available for these techniques. 

FCL/PLC Reconstruction

We have previously described our FCL and PLC reconstruction technique175 (Fig. 56-38). Dissection is carried through to the IT band. A three-window technique, as described by LaPrade et al.,27,108 is performed. We create one window through the midsubstance of the IT band all the way to Gerdy’s tubercle distally, a second window between the IT band and the biceps femoris, and a third window posterior to the biceps femoris. We expose the peroneal nerve and protect it, using a vessel loop. Once adequate exposure is obtained, we drill a 9-mm-diameter × 20-mm-deep socket at the site of the popliteus attachment. We secure our graft, typically an Achilles tendon allograft with a bone block, in the socket with an interference screw for bone-on-bone fixation. We then create a track between the popliteal hiatus and the posterior aspect of the fibula and pass the graft from posterior to anterior. We then expose both the anterior and posterior aspects of the fibular head and neck junction and, starting at the AL head and neck junction, we drill a 7-mm tunnel to the PM tubercle. We pass the graft through the fibular tunnel from posterior to anterior, re-creating the popliteus tendon and popliteofibular ligament portion of the reconstruction. We then find the isometric point on the femur just proximal and posterior to the lateral epicondyle and drill a Beath pin through the femur and create a 7-mm-diameter × 40-mm-deep socket over the Beath pin. We bring the graft from the fibula to the femur to re-create the FCL portion. Using the Beath pin to pull the sutures through the femur, we secure the FCL portion of the graft with double fixation with a BioComposite interference screw in the socket and a suspensory button on the medial femoral cortex. Before passing the graft, we place three suture anchors at the PL articular margin for later capsular imbrication. We pass the sutures through the capsule but do not tie them. Once the graft construct is completed and, with the leg in full extension, we tie the sutures to imbricate the capsule. We then close the capsule over the top of the construct and close the IT band. Prior to skin closure, we also tighten the lateral gastrocnemius to the back of the biceps to provide a little more PL support. It is important to note that for stability this technique requires an intact proximal tibiofibular joint as there is no direct tibial fixation. 
Figure 56-38
 
A: FCL and posterolateral corner reconstruction technique. and (B) the posterolateral capsule imbricated to the graft construct.
 
(From Schechinger SJ, Levy BA, Dajani KA, Shah JP, Herrera DA, Marx RG. Achilles tendon allograft reconstruction of the fibular collateral ligament and posterolateral corner. Arthroscopy. 2009;25(3):232–242, with permission).
A: FCL and posterolateral corner reconstruction technique. and (B) the posterolateral capsule imbricated to the graft construct.
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Figure 56-38
A: FCL and posterolateral corner reconstruction technique. and (B) the posterolateral capsule imbricated to the graft construct.
(From Schechinger SJ, Levy BA, Dajani KA, Shah JP, Herrera DA, Marx RG. Achilles tendon allograft reconstruction of the fibular collateral ligament and posterolateral corner. Arthroscopy. 2009;25(3):232–242, with permission).
A: FCL and posterolateral corner reconstruction technique. and (B) the posterolateral capsule imbricated to the graft construct.
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LaPrade et al. recently reported on an “anatomic” FCL/PLC reconstruction technique107 that was first developed and tested in the biomechanics laboratory108 (Fig. 56-39). The primary difference between this technique and ours is that this technique requires transtibial tunnels for the two-tailed approach. Using a standard lateral approach, and dissecting down to the level of the biceps femoris, an incision is made just posterior to the biceps femoris and the peroneal nerve is identified and protected. The fibular head is exposed via the FCL-biceps bursa and the insertion of the FCL on the fibular head is identified. Focus is next turned to drilling the fibular and tibial tunnels. A 7-mm tunnel is drilled from the insertion of the FCL anterolaterally to the insertion of the PFL posteromedially. A 9-mm tunnel is drilled through the tibia from anterior to posterior going from just distal and medial to Gerdy’s tubercle and exiting at the popliteus sulcus on the posterior tibia. The IT band is split and the FCL and popliteus tendon insertions on the femur are identified. Two parallel 9 × 20-mm-deep sockets are drilled over K-wires inserted in an AM direction from the popliteus tendon and FCL insertions exiting the femur proximal and medial to the medial epicondyle and adductor tubercle. Two separate tendon grafts are prepared using an Achilles tendon allograft that is at least 22 cm long and split lengthwise. The bone blocks for each graft are sized to fit the 9 × 20-mm femoral tunnels and are fixed into the femur with interference screws. The graft re-creating the popliteus tendon is passed through the popliteus hiatus and then through the tibial tunnel from posterior to anterior. The second graft is used to re-create the FCL and PFL and is passed deep to the superficial layer of the IT band, through the fibular tunnel from anterior to posterior and then through the tibial tunnel from posterior to anterior. The grafts are cycled and fixed with a bioabsorbable interference screw and backed up with a bone staple on the anterior tibia (Fig. 56-40). 
Figure 56-39
 
A: Posterior and (B) lateral views of “anatomic” FCL and posterolateral corner reconstruction technique as described by LaPrade et al. (From LaPrade RF, Johansen S, Wentorf FA, Engebretsen L, Esterberg JL, Tso A. An analysis of an anatomical posterolateral knee reconstruction: an in vitro biomechanical study and development of a surgical technique. Am J Sports Med. 2004;32(6):1405–1414, with permission).
A: Posterior and (B) lateral views of “anatomic” FCL and posterolateral corner reconstruction technique as described by LaPrade et al. (From LaPrade RF, Johansen S, Wentorf FA, Engebretsen L, Esterberg JL, Tso A. An analysis of an anatomical posterolateral knee reconstruction: an in vitro biomechanical study and development of a surgical technique. Am J Sports Med. 2004;32(6):1405–1414, with permission).
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Figure 56-39
A: Posterior and (B) lateral views of “anatomic” FCL and posterolateral corner reconstruction technique as described by LaPrade et al. (From LaPrade RF, Johansen S, Wentorf FA, Engebretsen L, Esterberg JL, Tso A. An analysis of an anatomical posterolateral knee reconstruction: an in vitro biomechanical study and development of a surgical technique. Am J Sports Med. 2004;32(6):1405–1414, with permission).
A: Posterior and (B) lateral views of “anatomic” FCL and posterolateral corner reconstruction technique as described by LaPrade et al. (From LaPrade RF, Johansen S, Wentorf FA, Engebretsen L, Esterberg JL, Tso A. An analysis of an anatomical posterolateral knee reconstruction: an in vitro biomechanical study and development of a surgical technique. Am J Sports Med. 2004;32(6):1405–1414, with permission).
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Figure 56-40
 
A: AP and (B) lateral fluoroscopic views of femoral and tibial tunnel placement and clinical photographs depicting (C) “anatomic” FCL and posterolateral corner reconstruction and (D) posterolateral capsule imbrication as described by LaPrade et al. (From Levy BA, Stuart MJ, Whelan DB. Posterolateral instability of the knee: evaluation, treatment, results. Sports Med Arthrosc Rev. 2010;18(4):254–262, with permission)
A: AP and (B) lateral fluoroscopic views of femoral and tibial tunnel placement and clinical photographs depicting (C) “anatomic” FCL and posterolateral corner reconstruction and (D) posterolateral capsule imbrication as described by LaPrade et al. (From Levy BA, Stuart MJ, Whelan DB. Posterolateral instability of the knee: evaluation, treatment, results. Sports Med Arthrosc Rev. 2010;18(4):254–262, with permission)
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A: AP and (B) lateral fluoroscopic views of femoral and tibial tunnel placement and clinical photographs depicting (C) “anatomic” FCL and posterolateral corner reconstruction and (D) posterolateral capsule imbrication as described by LaPrade et al. (From Levy BA, Stuart MJ, Whelan DB. Posterolateral instability of the knee: evaluation, treatment, results. Sports Med Arthrosc Rev. 2010;18(4):254–262, with permission)
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Figure 56-40
A: AP and (B) lateral fluoroscopic views of femoral and tibial tunnel placement and clinical photographs depicting (C) “anatomic” FCL and posterolateral corner reconstruction and (D) posterolateral capsule imbrication as described by LaPrade et al. (From Levy BA, Stuart MJ, Whelan DB. Posterolateral instability of the knee: evaluation, treatment, results. Sports Med Arthrosc Rev. 2010;18(4):254–262, with permission)
A: AP and (B) lateral fluoroscopic views of femoral and tibial tunnel placement and clinical photographs depicting (C) “anatomic” FCL and posterolateral corner reconstruction and (D) posterolateral capsule imbrication as described by LaPrade et al. (From Levy BA, Stuart MJ, Whelan DB. Posterolateral instability of the knee: evaluation, treatment, results. Sports Med Arthrosc Rev. 2010;18(4):254–262, with permission)
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A: AP and (B) lateral fluoroscopic views of femoral and tibial tunnel placement and clinical photographs depicting (C) “anatomic” FCL and posterolateral corner reconstruction and (D) posterolateral capsule imbrication as described by LaPrade et al. (From Levy BA, Stuart MJ, Whelan DB. Posterolateral instability of the knee: evaluation, treatment, results. Sports Med Arthrosc Rev. 2010;18(4):254–262, with permission)
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MCL/PMC Reconstruction

For MCL reconstructions, our preferred technique has been described by Marx et al.128 Through a medial incision, we identify the isometric points on the femur radiographically as described by LaPrade et al.219 with a guide pin. We then make an approximately 3-cm incision directly down to the femur. We create a 9-mm socket approximately 25-mm deep and dock our Achilles tendon allograft with a bone block into the socket and secure it with an interference screw. Typically, the ACL and PCL reconstructions require a small AM proximal tibial incision. Through that incision, we can create a tunnel under the sartorius expansion up to the MCL femoral attachment site and pass the graft down through the tunnel to the distal tibia. LaPrade has also shown that the MCL has three points of fixation: (1) on the femoral side of the isometric point just proximal and posterior to the medial epicondyle, (2) at the proximal tibia about 1.5 cm below the joint line, and (3) distal to the insertion of the pes tendons approximately 6 mm below the joint.104,219 We therefore follow the 3-point fixation principle and place two anchors at the proximal aspect of the two superficial MCL attachment sites on the tibia and with the knee in full extension secure the graft with the anchors. For the distal fixation, we use a suture post and ligament washer construct with a large 3.5 bicortical screw and an 18-mm spiked washer (Fig. 56-41). Using a locked whip stitch running up and down the Achilles tendon graft, we tie the sutures around the post. This provides double fixation of the graft on the tibia with both the soft tissue spikes into the graft and sutures around the screw post. 
Figure 56-41
MCL reconstruction using an Achilles tendon allograft
 
(From Levy BA, Stuart MJ. ACL, PCL, and medial-sided injuries of the knee. In: Fanelli GC, ed. The Multiple Ligament Injured Knee: A Practical Guide to Management. New York: Springer; 2013;255–265, with permission).
(From Levy BA, Stuart MJ. ACL, PCL, and medial-sided injuries of the knee. In: Fanelli GC, ed. The Multiple Ligament Injured Knee: A Practical Guide to Management. New York: Springer; 2013;255–265, with permission).
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Figure 56-41
MCL reconstruction using an Achilles tendon allograft
(From Levy BA, Stuart MJ. ACL, PCL, and medial-sided injuries of the knee. In: Fanelli GC, ed. The Multiple Ligament Injured Knee: A Practical Guide to Management. New York: Springer; 2013;255–265, with permission).
(From Levy BA, Stuart MJ. ACL, PCL, and medial-sided injuries of the knee. In: Fanelli GC, ed. The Multiple Ligament Injured Knee: A Practical Guide to Management. New York: Springer; 2013;255–265, with permission).
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Newer “anatomic” MCL/PMC reconstruction techniques have been developed that have been shown biomechanically to restore native stability without overconstraint to knees with complete MCL and posterior oblique ligament injuries.25 Clinical and functional outcomes of these techniques are pending (Fig. 56-42). 
Figure 56-42
New “anatomic” medial side reconstruction of the superficial MCL (sMCL) and posterior oblique ligament (POL).
 
(From Coobs BR, Wijdicks CA, Armitage BM, Spiridonov SI, Westerhaus BD, Johansen S, et al. An in vitro analysis of an anatomical medial knee reconstruction. Am J Sports Med. 2010;38(2):339–347, with permission).
(From Coobs BR, Wijdicks CA, Armitage BM, Spiridonov SI, Westerhaus BD, Johansen S, et al. An in vitro analysis of an anatomical medial knee reconstruction. Am J Sports Med. 2010;38(2):339–347, with permission).
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Figure 56-42
New “anatomic” medial side reconstruction of the superficial MCL (sMCL) and posterior oblique ligament (POL).
(From Coobs BR, Wijdicks CA, Armitage BM, Spiridonov SI, Westerhaus BD, Johansen S, et al. An in vitro analysis of an anatomical medial knee reconstruction. Am J Sports Med. 2010;38(2):339–347, with permission).
(From Coobs BR, Wijdicks CA, Armitage BM, Spiridonov SI, Westerhaus BD, Johansen S, et al. An in vitro analysis of an anatomical medial knee reconstruction. Am J Sports Med. 2010;38(2):339–347, with permission).
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Once all incisions are closed, we use elastic stockinette over our dressings and then place the patient in a hinged knee brace. If we have performed an ACL, PCL, and medial-sided reconstruction, we typically protect the MCL by placing the brace into a varus mold. If, however, for an ACL, PCL, and lateral-sided reconstruction, we mold the brace into a valgus to unload the lateral side. If both the medial and lateral sides have been reconstructed, the brace is kept in a neutral position. 

Postoperative Care

Each patient should have his or her postoperative rehabilitation protocol individually tailored according to the specific surgical intervention. We typically follow the postoperative rehabilitation protocol described by Fanelli and Edson,42,45 although numerous protocols are available. In the Fanelli and Edson protocol, the leg is kept non–weight bearing in a brace molded to protect the reconstructed ligaments and locked in full extension for 3 weeks. After that time, the patient begins passive range-of-motion (ROM) exercises. The patient remains toe-touch weight bearing for an additional 6 weeks and then may progressively increase their weight bearing. The brace is kept on full-time, even during therapy, except for showers. After 6 weeks, closed chain strengthening and proprioceptive exercises are initiated. It is especially important that no hamstring activation is performed for 4 to 6 months depending on the extent of the PCL and PLC reconstructions. After 8 weeks, the patient is prescribed a custom unloader brace that they wear for all activities during the first year postoperatively and for all athletic activities for life. Patients typically are able to return to full activities at 9 to 12 months postoperatively. 
Stannard et al.190 and LaPrade et al.107 have also described their rehabilitation programs with good outcomes. The rehabilitation program prescribed by Stannard et al. has the patient initiating ROM on postoperative day 1 with partial weight bearing for the first week followed by progressive weight bearing as tolerated. They advocate concentrating on early ROM and closed chain strengthening as dictated by the cruciate ligament injuries.190 Similarly, LaPrade et al.107 have their patients perform isometric strengthening (quadriceps sets and straight leg raises) in the brace and ROM exercises out of the brace for the first 2 weeks postoperatively. From 2 to 6 weeks, patients continue to work on non–weight bearing strengthening exercises and ROM with a goal of having full ROM by 6 weeks. Patients remain non–weight bearing for the first 6 weeks and then slowly progress to full weight bearing once they have no limp and begin progressive resistance strength training and proprioceptive exercises. They also advocate avoiding active isolated hamstring exercises for at least the first 4 months. Patients may be cleared for return to activity after 9 months if they have met strength and stability goals. 

Potential Pitfalls and Preventive Measures

One of the most important pitfalls during multiligament reconstruction surgery is damaging the neurovascular bundle during PCL tunnel reaming. Damage to these structures can be limb-threatening and cause severe debilitation. The neurovascular structures of the posterior knee, particularly the popliteal artery and tibial nerve, are at risk of injury due to their close proximity to the posterior tibia and PCL. They are most commonly injured by the guide pin being advanced too far, the guide pin inadvertently advancing during tunnel reaming, or excessive posterior excursion of the drill bit during reaming. Damage to the popliteal artery may be missed if a tourniquet is inflated; therefore, many surgeons will not inflate the tourniquet during PCL tunnel reaming. Preventing damage to the posterior neurovascular structures of the knee can be accomplished by (1) drilling the tunnels with the knee flexed to 90º to allow the neurovascular bundle to fall away from the tibia into the popliteal space; (2) using an instrument such as a tibial PCL guide or 90º curette to prevent the guide pin or drill bit from advancing too far; and (3) using intraoperative fluoroscopy to confirm guide pin or drill bit position relative to the posterior tibial border and PCL facet (Fig. 56-43). 
Figure 56-43
 
Intraoperative lateral fluoroscopic views of (A) guide pin and (B) and (C) reamer during PCL tunnel reaming; note proximity to popliteal artery repair vessel clips.
Intraoperative lateral fluoroscopic views of (A) guide pin and (B) and (C) reamer during PCL tunnel reaming; note proximity to popliteal artery repair vessel clips.
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Intraoperative lateral fluoroscopic views of (A) guide pin and (B) and (C) reamer during PCL tunnel reaming; note proximity to popliteal artery repair vessel clips.
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Figure 56-43
Intraoperative lateral fluoroscopic views of (A) guide pin and (B) and (C) reamer during PCL tunnel reaming; note proximity to popliteal artery repair vessel clips.
Intraoperative lateral fluoroscopic views of (A) guide pin and (B) and (C) reamer during PCL tunnel reaming; note proximity to popliteal artery repair vessel clips.
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Intraoperative lateral fluoroscopic views of (A) guide pin and (B) and (C) reamer during PCL tunnel reaming; note proximity to popliteal artery repair vessel clips.
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Management of Adverse Outcomes and Unexpected Complications in Knee Dislocations

Complications can occur at any point during the assessment and treatment of knee dislocations. Undoubtedly, the most significant is the failure to recognize a significant vascular injury. In the case of frank dysvascularity this is a rare occurrence, nonetheless, failure to restore perfusion to the lower limb within 6 to 8 hours may carry with it up to an 86% amputation rate.67,69,97 Assuming that a vascular injury is recognized, further mistakes can be made in failing to appropriately treat these lesions. Revascularization is strongly recommended to avoid chronic claudication or future dysvascular events in these patients. Moreover, surgical repair and/or reconstruction of an unstable joint is contraindicated (neither acutely nor in the longer term) without an intact arterial tree.69 
Similarly, neurologic injury must be recognized early and treatment initiated in the form of splinting and joint mobilization at the foot and ankle. If these steps are not taken, the resulting equinus contracture will impair ambulation and can preclude future treatment options such as tendon transfer. 
Most surgical reconstructive procedures described for dislocated knees are complex, invasive, and often lengthy. As with any such operative intervention then, there are a myriad of potential complications that can occur intraoperatively and postoperatively. Those adverse events specific to knee dislocation surgery will be discussed in some detail, but surgeons should always be mindful of the possibility for general anesthetic complications, infection, and venous thromboembolism and take appropriate preventative measures. 
Intraoperative vascular injury is always a risk when addressing posterior ligamentous and capsular injury. A prepared surgeon will have this in mind especially when releasing scar tissue posteriorly, drilling tibial PCL or PL reconstructive tunnels from anterior to posterior, and when making posterior incisions or portals in general. A vascular surgeon should be available for prompt intraoperative consultation when planning procedures that might involve these steps. If arterial bleeding is encountered, the anesthetist should be notified immediately, the reconstructive procedure halted, and the vascular surgeon consulted on a stat basis. If a tourniquet is not in use, then one should be applied proximally. Direct pressure and/or packing can be applied if an open approach has been used to gain posterior exposure. In the case of a vascular injury during an arthroscopic case, a tourniquet will likely control arterial bleeding. If this is not the case, and bleeding continues uncontrolled, an extended PM incision can be employed to gain proximal control of the vessel as a provisional step. Definitive management will involve exploration by a vascular surgeon with potential repair and/or bypass of the injured vessel. 
Although not usually a problem with most knee surgeries, excess intraoperative blood loss is a possibility with multiligament reconstruction given the length of time that can be required for complex procedures. Compounding this is the fact that some of the procedures may have to be completed without the benefit of tourniquet. Tourniquet use must be managed strategically to avoid prolonged compression of neurovascular structures. In patients who have had previous vascular procedures, tourniquet use may be contraindicated completely. These patients may also be on chronic anticoagulation. In such cases, the surgeon may choose less complex or lengthy procedures or even forgo operative intervention completely because of the difficulties imposed by uncontrolled bleeding. 
Because of the length of the procedures, meticulous attention must be paid to intraoperative positioning and padding of extremities and bony prominences. Insertion of a Foley catheter should also be considered after the induction of anesthesia. Regional anesthetics may be used as an adjunct intraoperatively or postoperatively, but the duration of surgery may exceed what can be expected from a spinal or epidural block. 
In the postoperative period, we highly recommend that patients be given thromboembolic prophylaxis.118 Intravenous antibiotic regimens are also recommended if allograft tissue is employed in reconstructive procedures or if extensive amounts of hardware are used for fixation. 
Superficial infections should be managed with appropriate antibiotics and immobilization of the affected soft tissues. Acute deep infections are rare but, when encountered, can be treated similarly to those regimens described after ACL reconstruction: serial I&D with primary retention of hardware and grafts. Those infections presenting beyond 3 weeks after surgery are likely established and will require more aggressive management. In these cases, it is recommended that all graft tissue and hardware be removed along with serial irrigation and extensive debridement (either open or arthroscopic). Intravenous antibiotics should be administered; the choice of medication is tailored to sensitivities obtained at surgery; the length of their administration is determined by serial serum analyses of the erythrocyte sedimentation rate and the C-reactive protein level. An external fixator may be required to manage joint subluxation in such cases. The timing of subsequent reconstructive procedures—and even the prudence thereof–is controversial. 
Heterotopic ossification (HO) is an unfortunately common complication following multiligament knee injury and/or reconstruction.134,192 In a series of 88 consecutive knee dislocations at a single level 1 trauma center, HO was observed in 30 (34%).207 The true incidence of HO after nonoperatively treated knee dislocations is unknown. In established cases, the knees are uniformly stiff and occasionally painful. Manipulation of the joint may not be helpful in restoring motion. Excision of heterotopic bone is usually successful but likely best done after the acute period of ossification has passed (usually approximately 3 months) and metabolic activity (based on serial bone scans) has normalized. Routine prophylaxis for HO in the setting of knee ligament reconstruction is controversial and not currently recommended. Furthermore, there is some evidence that the use of nonsteroidal anti-inflammatory medications may interfere with graft integration.23,33 
Although not formally thought of as complications, residual laxity and/or stiffness after multiligament reconstruction are unfortunately common “adverse events.” The relatively high frequency of these outcomes likely reflects the extent of these injuries as well as deficiencies of current reconstructive procedures to consistently restore optimal ligament balance around the joint. In general, it is thought that a “looser” yet mobile joint is more functional and better tolerated than a knee that is more stable yet with a reduced range of motion.82,186 
There are currently no long-term outcome studies to help predict the potential for, and rate of, posttraumatic arthritis in patients who have sustained a knee dislocation. Given the relatively high rate of arthritic changes observed following isolated ACL reconstruction, it is reasonable to predict that multiligament reconstructive procedures also carry some risk of similar degenerative changes.91,147,173 The rate of progression and magnitude of such changes likely depend not only on the extent of ligamentous injury and the effectiveness of surgery in restoring joint balance but also on the presence of associated injury—particularly that to the articular cartilage and meniscus (Table 56-5). 
Table 56-5
Common Adverse Outcomes and Complications After Knee Dislocation
DURING ASSESSMENT
Unrecognized vascular injury
Untreated vascular injurya
Unrecognized/untreated nerve injury
Unrecognized compartment syndrome
Intraoperative
Vascular injury
Bleeding
Postoperative
Infection
Deep venous thrombosis/thromboembolic phenomena
Heterotopic ossification
Residual joint laxity
Recurrent joint subluxation and/or dislocation
Stiffness
Arthritis
X

Authors’ Preferred Treatment for Knee Dislocations

 
 
Central Pivot (ACL/PCL) Injury
 

In the setting of a central pivot (ACL/PCL) injury (KD II) in the absence of collateral ligament disruption, our current practice is to allow the patient to rehabilitate the knee, reduce the swelling, reestablish full range of motion and quadriceps strength, and then perform a delayed ACL/PCL reconstruction. Similar to an isolated ACL injury,183,216 the rate of arthrofibrosis has been shown to be higher if patients undergo acute surgical reconstruction.138,214 We, therefore, in this particular ligamentous injury, allow the patient to completely rehabilitate the knee preoperatively, which normally takes about 6 to 8 weeks from the time of injury and then perform delayed ACL/PCL reconstructions, using the techniques described previously. Our preferred technique in this situation is all inside ACL and all inside PCL reconstructions that have the benefit of sockets instead of full tunnels that may minimize difficulties in the setting of future revisions should they become necessary. Rehabilitation follows our standard rehabilitation protocol as outlined previously.

 
ACL, PCL, and Medial-Side Injury
 

The ACL/PCL/medial-sided injury (KD-IIIM) is managed in numerous ways and is highly dependent on the extent of disruption to the medial-sided structures as well as the specific location of the medial-sided disruption.

 

In the setting of a distal MCL tear where the MCL is resting superficial to the pes tendons (the so-called “Stener lesion” of the knee), we feel that the rate of healing for this MCL avulsion is extremely poor. In that case, we recommend combined MCL repair of the distal avulsion and early ACL/PCL reconstruction at approximately 2 to 3 weeks from the time of injury. Waiting longer than 2 to 3 weeks makes it more difficult to discern the anatomical structures on the medial side of the knee for appropriate repair. Performing surgery before the 2- to 3-week period increases the risk of arthrofibrosis as noted previously. Our current repair technique involves ensuring 3-point fixation of the MCL. Since the femoral side is still intact, we need two distal points of fixation. We place suture anchors at the proximal tibial superficial MCL attachment site and pass the sutures through the tissue but wait to tighten them until we have completed the distal avulsion repair. The distal MCL repair is performed using a modified locking Krackow stitch weaving up and down the anterior and posterior borders of the ligament creating a small slit in the distal portion of the native ligament. With the knee flexed to 30º, we secure the MCL distally with a suture post and spiked ligament washer construct as described previously. Finally, the superficial MCL sutures at the tibial joint line are tied down with the knee in full extension. If necessary, the posterior oblique ligament and PL capsule are imbricated with a horizontal mattress suture technique to the native MCL ligament. This is also done with the leg in full extension to avoid capturing the knee.

 

In the setting of an ACL/PCL/MCL disruption where there is midsubstance stretch of the MCL as seen on the MRI, repairing the ligament is typically not very effective and we recommend ACL/PCL/MCL reconstructions. This is performed at approximately 6 to 8 weeks postinjury once the soft tissues have settled down and the knee is rehabilitated. Our preferred MCL reconstruction technique uses an Achilles tendon allograft with bone block as described previously.

 

In the setting of an ACL/PCL/MCL disruption with proximal (femoral) MCL avulsion, oftentimes the MCL may heal without surgery. Similarly to a combined ACL and MCL injury with femoral avulsion, we allow the patient to rehabilitate the knee, regain range of motion, and then test the medial-sided structures for integrity after 6 to 8 weeks. If the MCL has healed, we perform delayed ACL and PCL reconstructions. However, if the MCL has not healed, we will perform ACL/PCL/MCL reconstructions accordingly. Alternatively, in certain patients, we will treat femoral MCL avulsions similar to a distal avulsion, using a spiked washer/suture post construct to repair the avulsed MCL at the MCL femoral attachment site. The same principles of timing and surgery as noted previously apply.

 

In the setting of a very extensive medial-sided disruption where there is injury to the proximal, distal, and midsubstance areas of the MCL, as well as injury to the PMC structures (medial head of the gastrocnemius, posterior oblique ligament, semimembranosus tendon, and pes tendons), we typically perform a staged reconstruction. Stage 1 consists of MCL repair with allograft augmentation followed by second-stage ACL and PCL reconstructions at approximately 6 to 8 weeks from injury. Because of the extensive medial-sided disruption in this particular setting, we typically prefer to address the medial-sided structures prior to 2 weeks from injury to avoid scarring that would prevent us from dissecting out the anatomical structures individually and repairing them back to their native sites in an appropriate fashion.

 

Therefore, as noted previously, timing, fixation, and whether or not we stage ACL/PCL/medial-sided repair and/or reconstructions depends on the extent of the injury as well as the specific location of the medial-sided disruption.

 
ACL, PCL, and Lateral-Sided Injury
 

As with ACL/PCL/medial-sided injuries, decision making with ACL/PCL/lateral-sided injuries (KD-IIIL) also depends on the specific location of the lateral-sided injury and the extent of the lateral-sided disruption.

 

Distally based avulsions of the lateral side of the knee have actually demonstrated reasonable success with repair. Shelbourne et al.182 have described the “en mass” repair techniques for such injuries that focus on repairing the PL capsule to the tibia as well as the FCL and biceps tendons to the fibula. In their study of 21 patients followed for a minimum of 2 years, the authors noted good objective and subjective success, using this technique. More recently, Geeslin and LaPrade59 described repair techniques for distal, midsubstance, and proximal avulsions of the FCL. Our preferred technique for distally based avulsions depends not just on the extent of the injury but also on the quality of the tissues and the age of the patient. For example, in the case of an ACL/PCL/lateral-sided injury with a distal avulsion where the capsule is detached from the tibia, the meniscus is separated from the capsule, and the biceps and FCL are torn off the fibula, we recommend early repair augmented with a graft when the quality of the tissue is not good. In young patients, we have found that the tissue quality is typically very good and if we can operate within 10 to 14 days prior to significant scarring, the anatomical structures can often all be identified, located, and repaired back to their native anatomical insertion sites. If after completion of fixation, the construct does not appear to be solid or the tissue is not strong, then we augment the repair with a reconstruction, using either hamstring tendon allograft or autograft tissue as described previously with our reconstruction technique.

 

In the case of an ACL/PCL/lateral-sided injury with midsubstance injury as noted on the MR image, we will typically let the patient rehabilitate the knee and perform delayed ACL/PCL/lateral-sided reconstructions at approximately 6 to 8 weeks from injury. In this case, being able to dissect out the anatomical structures is less critical as we are bypassing all these structures with our graft construct. This approach allows any swelling to subside and the patient to reestablish full range of motion, thereby decreasing the ultimate risk of arthrofibrosis.

 

In the setting of ACL/PCL/lateral-sided injuries with proximal avulsions, we have found poor success rates with repair alone for the avulsed popliteus tendon and FCL.115 Therefore, in this setting, similar to the midsubstance MCL injuries, we prefer ACL/PCL/lateral-sided reconstructions in a delayed fashion at approximately 6 to 8 weeks from the time of injury for the reasons noted previously.

 
ACL, PCL, Medial, and Lateral-Sided Injury
 

In the setting of global instability with ACL/PCL/medial/lateral-sided injuries (KD-IV), all of the same principles we just described for medial and lateral-sided injuries apply here as well. For example, if there is extensive medial-sided disruption and a distally based avulsion of the lateral-sided structures, then we perform a staged procedure. We fix the medial-sided structures acutely, augmenting with graft if the tissues are not acceptable, followed by immediate repair of the distally avulsed tissues, again augmenting with graft if necessary. We then allow the patient to rehabilitate the knee and then perform second-stage ACL and PCL reconstructions in a delayed fashion. However, if there is significant intrasubstance signal change of both the medial and lateral sides of the knee, we allow the patient to rehabilitate the knee, regain range of motion, and perform a multiligament knee reconstruction of the ACL, PCL, MCL/PMC, and FCL/PLC approximately 3 to 6 weeks from injury once the swelling has subsided and the patient has reestablished a reasonable range of motion.

 
Fracture-Dislocations
 

As a general rule, we prefer to treat all fractures first, restoring bony anatomy and allowing the bone to heal, and then perform delayed ligament reconstructions later. Having said that, there are times when there are fractures of the proximal tibia with bony avulsions of the collateral ligament at which point we would address all these bony avulsions (ligament repairs) at the time of the fracture fixation.

 
Other Injury Patterns
 

Although there are other combinations of ligamentous injuries, for example, ACL/medial side, ACL/medial/lateral side, or PCL/lateral side, all of the principles outlined previously pertain to any other combinations of injuries. For example, a PCL/lateral-sided injury would be treated in the same way as an ACL/PCL/lateral-sided injury. Similarly, an ACL/medial-side injury would be treated with the same principles as the ACL/PCL/medial-side injury.

Outcomes, Controversies, and Future Directions Related to Knee Dislocations

Operative Versus Nonoperative Management for Knee Dislocations

Four main studies have compared operative treatment with nonoperative treatment; all are level III or IV retrospective studies.157,167,169,220 In the largest of these, Richter et al.167 compared 63 patients treated with a combination of early and late surgery with 26 patients treated nonoperatively. Statistically superior outcomes were demonstrated in the surgical group in terms of the Lysholm score (78.3 vs. 64.8), the Tegner score (4.0 vs. 2.7), IKDC activity level, and the Lachman test, as well as working ability and sports participation. 
The operative management of multiple ligament injuries, compared with nonoperative management, has been shown to result in superior clinical and functional outcomes in meta-analyses, systematic reviews, and evidence-based reviews.31,116,155 Studies comparing these two treatment options consistently show improved Lysholm scores, as well as higher rates of excellent and good IKDC scores with operative management.31,157,167,169,220 
With regard to range of motion and contractures, an evidence-based review of articles published between 2000 and 2010 demonstrated no statistically significant differences between operative and nonoperative groups; however, there were statistically significant differences between the two cohorts in return to employment and return to sport.155 This is in contrast to a meta-analysis published in 2001 by Dedmond and Almekinders,31 which failed to show that return to preinjury employment or athletic activity was improved by operative management. It may be that the 2001 study had insufficient numbers to detect a significant difference, or that the outcomes of return to work and/or sport were not considered at that time, or it may be that surgical techniques have improved over the last decade. Interestingly, in the review of 31 articles published between 2000 and 2010, the aggregate average Lysholm scores were 84.3 and 67.2 for the operative and nonoperative cohorts, respectively; these are nearly identical to the average Lysholm scores published in 2001 for the operative and nonoperative groups (85.2 and 66.5).31,155 
Most surgeons with experience in multiligament knee injuries agree that operative management is likely the gold standard.47 However, some indications for nonoperative management remain, including severe polytrauma, head injury, advanced age, medical comorbidities, poor patient compliance, and soft tissue compromise about the knee.155 Thus, despite evidence that operative management is superior, there will always remain a subset of patients for whom—usually due to coexistent injury or illness—nonoperative management is prudent. Moreover, the timing and extent of surgery may also require modification based on extenuating patient or injury factors. 

Early Versus Delayed Surgical Management for Knee Dislocations

Early surgery is usually defined as surgical repair or reconstruction performed less than 3 weeks after injury. Three weeks is thought to be the latest time at which damaged structures are still anatomically identifiable, with minimal tissue retraction, and able to accommodate suture “purchase” for repair. Recognizing that some degree of initial capsular healing may be advantageous to allow arthroscopic distension of the joint (and avoid the potential for fluid extravasation into surrounding tissue compartments), the optimal window for surgery is likely between 10 and 20 days after injury.45,117 
Harner et al.,79 in a retrospective study of 31 consecutive patients with a knee dislocation, compared 19 patients who were treated less than 3 weeks after injury, and 12 patients managed with late reconstruction. The mean Lysholm score was 91 points for the acutely reconstructed knees and 80 points for the chronically reconstructed knees, a trend that approached statistical significance (P = 0.07). According to the final overall IKDC rating, no knee in either group received a normal overall IKDC rating. Of the 11 “nearly normal knees,” all but one was treated acutely. 
Tzurbakis et al.209 retrospectively compared 35 early against 9 late surgical interventions, finding a statistically significant improvement in Lysholm score in the early group. In three other studies comparing early and late surgical treatment of the multiligament injured knee, no statistically significant difference in knee outcome scores was demonstrated; however, there was a trend toward better outcomes with acute treatment.45,122,214 Unfortunately, the patterns of injury and the surgical treatment vary from paper to paper and thus preclude data pooling or direct comparison. 
There have been two recent systematic reviews that evaluate the nuances of surgical treatment of knee dislocations and multiligament knee injury in general. Levy et al.116 demonstrated that early surgical treatment resulted in higher mean Lysholm scores and a higher percentage of excellent and good IKDS scores (47% vs. 31%) than delayed surgery. No significant differences were observed in mean range of motion or flexion, but patients treated with early surgery had statistically higher sports activity scores. In 2009, a second systematic review by Mook et al.138 found that acute treatment of knee dislocations led to increased anterior instability compared with chronic treatment. No statistically significant difference was detected with posterior instability, or varus or valgus laxity based on surgical timing. They also demonstrated that acute treatment is more likely to result in flexion loss of >10° versus chronic treatment. This difference was more pronounced when patients were immobilized in the postoperative period. In addition, the number of patients requiring manipulation under anesthesia or operative arthrolysis was increased in the acute treatment group. Staged treatment (defined as a combination of repair and reconstruction, in both the acute and chronic settings) resulted in superior subjective outcomes than either acute or chronic treatment. 
It should also be emphasized that—in comparing early and delayed surgical groups—the latter likely had symptoms necessitating further intervention, a fact that imposes an inherent bias in patient selection and assessment of outcomes. There is likely a subset of patients in the early groups that may have done well without surgery (or with a delayed approach). This is likely not the case for the delayed groups in which (given that the treatments were not randomly allocated) all patients required surgery to address ongoing and intolerable symptoms. A well-designed randomized trial would likely help eliminate this potential bias and go a long way to answering the question of when surgery is optimally performed following knee dislocation. 
The limited data available would seem to suggest that early surgical intervention affords the best opportunity to maximize outcomes following multiligament knee injury. There are admittedly some challenges to getting the acutely multiligament injured knee to surgery within a 3-week window. Some knee dislocations present late, as the knee spontaneously reduces and the severity of the injury is underestimated. In addition, there can sometimes be no effusion due to the capsular disruption, further hampering timely recognition of the extent of the injury. In addition, concomitant injuries can prohibit early surgery, including open knee dislocations, vascular injuries, and associated head, abdominal, or chest trauma, for which the best approach may be delayed surgery. 

Repair Versus Reconstruction for Knee Dislocations

The majority of surgical techniques advocated for treating multiligament knee injuries describe either repair of the torn structures, reconstruction with either allograft, autograft, or synthetic ligaments, or combinations thereof. Apart from graft choices, reconstructive options include various surgical techniques, across very heterogeneous groups of patients. Few comparative studies are available. In general, two philosophies of surgical treatment dominate the literature: early repair versus delayed reconstruction. 
Owens et al.148 performed open primary repair of ligaments in 30 consecutive knee dislocations within the first 2 weeks, including primary repair of the ACL and PCL. A mean postoperative Lysholm score of 89 was reported, with minimal permanent loss of range of motion and good stability.148 In that series, the lack of comparison to cruciate reconstruction is problematic, and many surgeons would feel unfamiliar with open repair in the current age of reconstruction. While the likelihood of encountering a cruciate ligament avulsion fracture amenable to direct repair is increased in the setting of knee dislocation, the incidence of stiffness has been suggested to be greater when directly fixing ACL avulsions.137,208 Furthermore, the long-term results of repairing isolated ACL injuries are generally thought to be inferior to modern reconstructive techniques.201 
Reconstruction of both the ACL and PCL has become popular, with good outcomes reported using autograft, allograft, and synthetic ligaments.40,42,79,96,164,214 Fanelli and Edson42 reported on the 2- to 10-year results of 35 arthroscopically assisted combined ACL and PCL reconstructions with a variety of grafts. Normal Lachman and pivot shift test results were found in 33 of 35 knees (94%), while a normal posterior drawer/tibial step off was found in 16 of 35 knees (46%).42 PCL reconstruction has been described using both single and double bundles, as well as with inlay and transtibial techniques.41,96,119,124,129,178 Mariani et al.127 looked at the outcome in groups of patients with ACL and PCL injuries with three surgical techniques: both cruciates repaired, both cruciates reconstructed, or ACL reconstruction combined with PCL repair. All three groups had very similar IKDC and Lysholm scores. It was noted that the direct repair of both cruciates had statistically significantly increased rates of posterior sag and lower rates of return to preinjury level, whereas the group of patients in whom both the ACL and the PCL were reconstructed had increased rates of return to sport. 
When considering high-grade lateral-sided injuries, it has traditionally been accepted that an avulsed FCL (whether from the femur or fibula), and popliteus tendon (from the femur), can and should be directly repaired acutely.40,42,56,79 In addition, direct repair of the PLC via en bloc advancement has been advocated by Shelbourne et al.,182 with good results reported; 15 of 17 patients had normal lateral laxity, and the mean IKDC score was 91.3. Direct comparisons of repair versus reconstructive approaches to high-grade lateral/PL injuries have been published recently. In 57 knees, Stannard et al.189 could not detect a statistically significant difference in Lysholm scores, IKDC scores, or return-to-work rates between the two groups. However, return to sport and objective stability were increased in the reconstruction group, leading the authors to recommend reconstruction as opposed to repair. In a consecutive series of patients with PLC injuries, Levy et al.115 initially repaired laterally sided injuries, before moving to ligament reconstruction; the 40% (4 of 10) failure rate in the repair group was reduced to a 6% (1 of 18) failure rate in the reconstruction group. Similarly, for high-grade medial sided injuries, Stannard et al.188 has demonstrated a failure rate of 20% (6 of 24) in the repair group and 4% (2 of 48) in the reconstruction group. 
In summary then, reasonable results have been reported with both early repair and early reconstruction of multiligament knee injuries. In the setting of FCL, popliteus, and MCL avulsions, although direct repair is a technically viable option and has been preferred in the past, recent evidence seems to suggest that reconstruction may be the superior technique. Most experienced multiligament surgeons would agree that ACL and PCL reconstructions are optimal for bicruciate injuries and the literature seems to support this opinion. Some controversy continues, however, as to the optimal management of high-grade collateral ligament injury. Repair has the advantage of restoring anatomy directly but is likely not sufficient in isolation. The optimal approach likely involves some combination of the two philosophies such as anatomic repair performed in a timely manner and supplemented with a concomitant reconstructive procedure. Such an approach affords the restoration of normal anatomic attachments provided by repair, with the added stability of the reconstruction to allow early motion and potentially prevent arthrofibrosis. 

Autograft Versus Allograft Reconstruction for Knee Dislocations

So many combinations of different autografts and allografts are described in the multiligament injury literature, with various reconstruction techniques, that attempting to differentiate outcomes is nearly impossible. Given the extreme insult to the joint and its soft tissue envelope at the time of dislocation, most surgeons are hesitant to add further morbidity by harvesting autograft tissue from the injured knee. Moreover, the integrity of autograft tissue may be compromised in the recently traumatized state. Conversely, the mechanical integrity of allograft, its sterility, and its ability to integrate into a foreign host are equally important concerns among surgeons who favor autograft harvest. Furthermore, the debate over the optimal preparation of allograft tissue continues with maintenance of structural integrity being weighed against the complete eradication of potential pathogens. Allograft is unavailable in many countries and centers. In other places, the cost of procuring the grafts may be prohibitive. For those surgeons who do employ allograft in the treatment of multiple ligament knee injuries, a specific conversation with the patient outlining its necessity and potential risks is essential. The issue of autograft versus allograft is likely another question that will only be effectively answered by a multicentered study. 

Postoperative Rehabilitation for Knee Dislocations

Rehabilitation is an important aspect of the treatment of knee dislocations following surgery and protocols described in the literature vary. The difficulty lies in achieving a balance between early mobilization to prevent stiffness and immobilization to promote healing and stability. 
A systematic review by Mook et al.138 suggested—seemingly paradoxically—that immobilizing knees after acute surgery for knee dislocation led to increased posterior instability versus a protocol of early mobilization. This trend was also seen in the incidence of postoperative varus and valgus laxity.138 These (statistically significant) findings would suggest that early mobilization was key to stability; however, within the chronic treatment groups varus laxity was increased with early mobilization. The same systematic review showed that immobilization after acute surgical treatment of knee dislocations increased the incidence of both flexion loss >10° and extension loss >5°. Patients were significantly more likely to have severely abnormal or poor outcomes and were significantly less likely to return to work. 
In 2002, Richter et al.167 compared 6 weeks of immobilization to functional rehabilitation (flexion to 60° allowed after 48 hours) in patients managed both operatively and nonoperatively. Statistically significant improvements were seen in the Lysholm and Tegner scores, but not the IKDC scores in patients treated with functional rehabilitation 
The postoperative use of a hinged knee external fixation device was compared to a hinged knee brace in a prospective randomized study of knee dislocations. Early results suggest reduced instability and reduced surgical failure rates with the use of the hinged external fixator.205 
A randomized comparison of early versus delayed rehabilitation protocols following acute (<3 weeks) multiligament surgery would be possible, but again subject to the issue of heterogeneity among patterns of injury and repair techniques. Given the more recent popularity of combined early repair and reconstruction, early motion may be a more favorable option to surgeons who in the past had been hesitant to mobilize acutely repaired tissues. 

Acknowledgment

The authors thank Scott A. Kuzma, MD, for his relentless dedication, time, and effort in the preparation of this chapter. 

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