Posterolateral corner injuries of the knee.
Article Type: Report
Subject: Knee (Injuries)
Knee (Research)
Knee (Care and treatment)
Knee (Diagnosis)
Authors: Frank, Joshua B.
Youm, Thomas
Meislin, Robert J.
Rokito, Andrew S.
Pub Date: 06/01/2007
Publication: Name: Bulletin of the NYU Hospital for Joint Diseases Publisher: J. Michael Ryan Publishing Co. Audience: Academic Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2007 J. Michael Ryan Publishing Co. ISSN: 1936-9719
Issue: Date: June, 2007 Source Volume: 65 Source Issue: 2
Topic: Event Code: 310 Science & research
Accession Number: 190052885
Full Text: Abstract

The posterolateral region of the knee is an anatomically complex area that plays an important role in the stabilization of the knee relative to specific force vectors at low angles of knee flexion. A renewed interest in this region and advanced biomechanical studies have brought additional understanding of both the anatomy and the function of posterolateral structures in knee stabilization and kinematics. Through sectioning and loading studies, the posterolateral corner has been shown to play a role in the prevention of varus angulation, external rotation, and posterior translation. The potential for long-term disability from these injuries may be related to increased articular pressure and chondral degeneration. The failure of the reconstruction of cruciate ligaments may be due to unrecognized or untreated posterolateral corner injuries. Various methods of repair and reconstruction have been described and new research is yielding superior results from reconstruction of this region.

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Isolated injuries to the posterolateral corner of the knee are rare and represent less than 2% of all ligamentous injuries. (1) These injuries are much more common as part of a multiligamentous pattern. Combined injury patterns have been demonstrated in 43% to 80% of patients with posterolateral injuries. (2-4) The anatomy and function of this region has gained the recent interest of researchers. Anatomic dissections and subsequent biomechanical studies have demonstrated discrete ligamentous structures, which Seebacher and colleagues (5) subsequently organized into three distinct layers. With improved comprehension of the anatomy and function of this region, one may better diagnose and treat these injuries. The role of surgical intervention is related to the potential for disability from chronic posterolateral instability. In addition, this injury pattern may affect the success of cruciate ligament reconstruction and, potentially, to advanced degeneration.

Anatomy and Functional Biomechanics

Multiple investigators have delineated the anatomy of this region. Seebacher and associates5 provided a detailed layer concept by dividing the structures into three layers, akin to the medial aspect of the knee. The first, being the most superficial, contains the iliotibial tract (ITT) and the biceps femoris. While the ITT is fundamentally thought of as inserting into Gerdy's tubercle, there are actually three insertions. One insertion blends into the intermuscular septum and inserts onto the supracondylar tubercle via Kaplan's fibers. The second inserts onto the patella and patellar ligament and the third inserts onto Gerdy's tubercle. (6) The first layer is also composed of the superficial aspect of the biceps femoris. The biceps consists of a long and short head and also has numerous insertions. The major insertion runs posteriorly to the ITT and inserts on the fibular head. The second layer is deep to the first and consists of the quadriceps retinaculum, anteriorly, as well as the patellofemoral ligaments, posteriorly. (5) The third layer, the deepest, can also be divided into a superficial and deep lamina. Superficial are the lateral collateral ligament (LCL) and the fabellofibular ligament. (7) The deep lamina of the third layer contains the popliteofibular ligament (PFL), arcuate ligament, and the popliteus muscle and tendon complex. (5)

Deep Anatomy (Fig. 1)

The LCL originates from the lateral distal femoral condyle and inserts onto the lateral aspect of the fibular head. The femoral site of origin is posterior to the popliteus origin (8) and the fibular site of insertion is distal to the insertions of the arcuate and PFL. The popliteus originates from the posterior aspect of the proximal tibia and passes through a hiatus in the coronary ligament (capsular attachment to the outer edge of the meniscus) as it inserts onto the lateral femoral condyle, inferior to the LCL origin. In addition, less than 20% of the population has attachments between the popliteus tendon and the lateral meniscus, which may aid in lateral meniscal movement and stabilization. (9)

The PFL connects the popliteus tendon to the posterior, proximal region of the fibular head. Its critical role in posterolateral stability has been extrapolated by recent research. (10) The arcuate ligament is a Y-shaped ligament with medial and lateral limbs. The lateral portion is formed from the fascial condensation over the posterior popliteus tendon. (5) Additional structures have been defined in this region that may contribute to posterolateral stability. These include the middle third of the capsular ligament, the lateral head of the gastrocnemius tendon, the lateral meniscus, and the posterolateral joint capsule.

Another reason for the complexity of the posterolateral region is the variability of the ligaments. A study by Sudasna and Harnsiriwattanagit (11) demonstrated only 68% of knees had a fabellofibular ligament and 24% had an identifiable arcuate ligament; however, in 98% of specimens, a fibular origin of the popliteus was identified, the PFL. Seebacher and coworkers (5) also noted variations. The posterolateral region of the knee was reinforced by only the arcuate ligament in 13% of knees and the fabellofibular ligament was the sole reinforcement in 20%. The investigators noted that 67% of knees had both structures. The fabellofibular ligament and the arcuate ligament may have an inverse relationship that embraces the nature of the fabella itself. In patients with a bony fabella present, a thick fabellofibular ligament was present in 82.8% of specimens. Furthermore, if the fabellofibular ligament was greater than 5 mm thick, the arcuate ligament was not present in any of the specimens. Conversely, in patients with a thin or indefinable fabellofibular ligament, 77.9% had a fabella with an elastic nature. In addition, a thin, or ill-defined fabellofibular ligament was accompanied by a well-defined arcuate ligament in 61.9% of specimens. (12) Further evidence of the wide range of variability in the anatomy of this region was demonstrated by Watanabe and colleagues, (13) who classified this region into seven major variants

All of the significant effort to define the structures of the posterolateral corner of the knee has given researchers and clinicians a better understanding of the functional biomechanics of the knee.

[FIGURE 1 OMITTED]

Overall, the posterolateral region of the knee provides anatomical restraint to varus forces, posteriorly directed forces, and external rotation forces. The contribution of each of the individual structures has been examined through anatomic dissection combined with sectioning studies. The main stabilizers of this region are the LCL, the PFL, and the popliteus muscle-tendon complex.

Superficially, the function of the ITT varies with knee flexion. With the knee in full extension, the ITT is an anterior structure. As the knee flexes, the ITT moves posteriorly and, thus, exerts an external rotation and posteriorly directed force on the lateral aspect of the tibia. (6) The biceps femoris functions to provide lateral stabilization as well as a dynamic external rotation force. (14)

The LCL offers a primary restraint to varus angulation and a secondary restraint to external rotation and posterior displacement. (15) The PFL has a cross-sectional area similar to that of the LCL (6.9 [mm.sup.2] vs. 7.2 [mm.sup.2]). (16) Various studies have shown the PFL to be consistently present. (11,16) Sectioning studies have revealed the role of the PFL is to resist excessive posterior translation, varus angulation, and external rotation (primary and coupled). (15) Under direct varus loading, the LCL fails first, followed by the PFL, and then the popliteus muscle belly. (16)

Through the work of multiple investigators, (10,17-25) it has been shown that sectioning of the posterolateral corner increases varus rotation, primary external rotation, primary posterior translation, and coupled external rotation (which combines movement in more than one plane; in this case, posterior translation with external rotation). The contribution of this region is mostly at lower angles of knee flexion. While the LCL is the primary restraint to varus at all angles of flexion, the contribution of the remainder of the posterolateral structures is greatest at 30[degrees] of knee flexion. (22)

The effect of this region on in situ posterior cruciate forces is also important. After complete sectioning of the posterolateral structures, tibia varus or external rotation causes increased force in the posterior cruciate ligament (PCL) between 45[degrees] and 90[degrees] of flexion. (22) Internal rotation force does not affect the PCL; however, after sectioning the posterolateral structures, the anterior cruciate ligament (ACL) does experience increased force at 0[degrees] to 20[degrees] of flexion on internal rotation. (22)

The converse may be true as well. The posterolateral structures experience increased forces when the PCL is compromised. Under posterior tibial load, the forces in the posterolateral structures increase from the intact state to the PCL-deficient state. In the intact knee, the forces decrease as the knee is flexed, which corresponds to the increased contribution of the PCL in high angles of flexion. After sectioning the PCL, the posterolateral structures experience increased forces at all levels of flexion. Under these conditions, the popliteus muscle acts as a major stabilizer. (26)

Clinical Relevance

Injury patterns predict both the clinical examination and the subsequent functional outcome. Isolated PCL injuries have long been thought to be clinically insignificant. That being said, it appears as though PCL injuries are not uncommon; 1% to 44% of all knee injuries involve PCL tears. (27) With these injuries, there is an increase in posterior translation, which increases on higher knee flexion; however, there is no increase in varus laxity or external rotation. (7) Isolated LCL tears demonstrate increased varus laxity (1[degrees] to 4[degrees]), greatest at 30[degrees]; however, the clinical implications of this have been difficult to define. (7)

Effect on knee function from injury varies widely. Injury to all of the posterolateral structures, with the PCL remaining intact, demonstrates maximally increased varus, external rotation, and posterior translation at 30[degrees] of knee flexion. As the knee is flexed up to 90[degrees], the majority of PCL fibers become taut, and there is some secondary restraint to varus and external rotation. At 90[degrees] of flexion, there is primary restraint to posterior translation. (17,23,28) When the PCL and the posterolateral structures are torn, the effect of the PCL at high angles of flexion is lost, and the knee experiences decreased restraint to varus, external rotation, and posterior translation at all angles of flexion. (7,23) When ACL injuries are combined with posterolateral corner injuries, the knee may experience increases in anterior and posterior translation, varus, coupled external rotation, and primary internal rotation. (25,29)

The clinical implications of injuries to this region relate to the outcome of cruciate reconstruction, as well as an effect on articular pressure and subsequent degeneration. Vogrin and colleagues (30) looked at in situ PCL forces in the intact knee, compared to the posterolaterally-deficient knee, under the testing condition of a posteriorly directed tibial force and an external rotation force. The PCL experienced higher loads when the posterolateral structures were sacrificed.

In relation to ACL reconstruction, O'Brien and associates (31) demonstrated the most common cause of failure of ACL reconstruction was unrecognized or untreated posterolateral rotatory instability. Noyes and coworkers (32) also illustrated the importance of the posterolateral corner in ACL reconstruction. They showed that 17 of 76 revision ACL reconstructions demonstrated unrecognized posterolateral rotatory instability.

Articular pressure also increases with ligament sectioning. Combined sectioning of the PCL and posterolateral complex increases patellofemoral pressures. Additionally, the posterior subluxation of the tibia, or "drop back," leads to increased quadriceps contraction required to extend the knee. Further, PCL sectioning leads to increased medial compartment pressures. (33)

Mechanism of Injury

Acute isolated posterolateral knee injuries are extremely rare and represent less than 2% of all ligamentous knee injuries. (1) The majority of these injuries occur as part of a combined injury pattern. The mechanism of injury usually relates to contact or noncontact mechanisms. Contact, or direct, injuries are due to sports (40%) or motor vehicle accidents. A posterolaterally directed force is exerted onto the proximal medial tibia, causing knee hyperextension with varus and external rotation. Noncontact mechanisms also involve a forceful hyperextension of the knee with concurrent tibial external rotation. Foot position may also play an important role. With the ankle in dorsiflexion, a fall results in the majority of the force moving through the patella; however, with plantarflexion, the proximal tibia strikes the ground or object.

Posterolateral corner injuries are rarely isolated. Concurrent ligamentous injury rate has been shown to range from 29% to 80%. (1,4,34,35) Magnetic resonance imaging studies (35) have revealed the potential for internal derangements of the knee that include both meniscal tears (29%) and osteochondral lesions (36%).

Presentation and Examination

The acutely injured patient will present with complaints of pain, effusion, and possibly gross deformity if a knee dislocation is present. Ecchymosis or skin abrasions on the anteromedial proximal tibia may be signs of a posterolateral injury. Motor or sensory symptoms in peroneal nerve distribution have been reported in 14% to 30% of patients. (14,36) Pulses and ankle-brachial indices (ABI) measures should be evaluated, as vascular injury also may be present.

The presentation of posterolateral injury will vary according to its acuity. Compared to the acute trauma setting, a chronic injury will most likely cause instability. In addition, there may be lateral joint line pain and difficulty with lateral movements or cutting activities. (14,37)

The physical examination for both settings should start with inspection of the overall limb alignment, limb length, and gait pattern. Varus malalignment of the extremity may not only predispose a person to posterolateral corner injury, but may lead to failure of treatment as well. With full extension or gait, the knee may buckle into hyperextension. Due to this instability, patients may ambulate with the knee in a flexed position. Patients also hold the ankle in equinus to prevent the knee from reaching full extension. A lateral or varus knee thrust may be visible. (14,37)

A variety of physical examination tests have been described for both posterior cruciate and posterolateral injuries. The basis for these tests stems from the aforementioned function of each region. It is important to understand the correct position of the knee for each test and to have a systematic approach in clinically evaluating the patient. The knee should be tested first for anterior-posterior laxity. The anterior and posterior drawer and Lachman tests are designed to evaluate the integrity of the cruciate ligaments. If either the PCL or posterolateral corner is injured, the knee may have assumed a posteriorly subluxed position. Anterior translation from this position can lead to a falsely positive anterior drawer or Lachman test. (38) This posterior resting position also leads to anterior translation of the tibia with quadriceps contraction, known as the quadriceps active test. The normal knee does not demonstrate this motion. The posterior drawer can be used to evaluate the PCL if done with the knee at 90[degrees] of flexion. At 30[degrees] of flexion, the test can be used to evaluate the posterolateral corner.

Varus and valgus laxity testing should be performed in full extension and then at 30[degrees] of flexion to isolate the collateral ligaments. Since the posterolateral corner resists posterior translation, external rotation, and varus at lower degrees of knee flexion, some combination of these movements are present in the individualized tests. (39) The posterolateral drawer sign is similar to the posterior drawer except the leg is externally rotated, approximately, 15[degrees]. The posteriorly directed force causes the lateral tibia plateau to move while the medial plateau does not translate. (40) The external rotation recurvatum test is performed by lifting the extremity by the great toe. A knee with a posterolateral corner injury should fall into hyperextension, varus, and external rotation. (3)

A variety of additional tests are available. The posterior external rotation test is a combination of a posterior force and an external rotation force, performed at 30[degrees] and 90[degrees] of knee flexion. Positive results at 30[degrees] indicate a posterolateral corner injury; however, positive results at 90[degrees] may be indicative of combined posterolateral corner and PCL injuries. (41) The dynamic posterior shift test is performed with the patient supine and the hip and knee flexed. The knee is then passively extended. A clunk or jerk can be felt as the tibia is reduced to near full extension. (42) With posterior lateral corner injuries, there may also be an appreciable element of rotation of the tibia on reduction.

The tibial external rotation test, or dial test, is performed at 30[degrees] and 90[degrees] of knee flexion. A supine or prone body position can be used. The relationship of the medial aspect of the foot to the femoral axis is examined. The normal values allow for 29[degrees] (10[degrees] to 45[degrees]) of external rotation at 30[degrees] of knee flexion. At 90[degrees] of knee flexion, tibial external rotation increases in normal subject to 37[degrees] (15[degrees] to 70[degrees]). (37) As this test also correlates to the presence of ligamentous laxity, the most useful application is a comparison between the affected and contralateral extremities. (43) Jakob and coworkers (14) described the reverse pivot shift test as taking the knee from 90[degrees] to 0[degrees] with a valgus load applied. The leg is held in external rotation and a clunk is felt similar to that of a pivot shift for an ACL injury. This test was examined by Cooper, in 1991, and found to be positive in up to 35% of normal knees. (43) Finally, Ferrari and colleagues (44) described a standing apprehension test. With the patient standing and the knee slightly flexed, the examiner places his thumbs on the anterolateral aspect of the lateral femoral condyle and applies a posteriorly directed force. The patient feels a sensation of "giving way" as movement of the condyle relative to the plateau is experienced.

Instrumented devices may also allow for objective measures of instability. The KT-2000 device is available for this purpose. The Lars Rotational Laxiometer (Lars Inc., Dijon, France) is another device capable of yielding objective values of instability. Normal side-to-side variation is, approximately, 4.4[degrees] at 90[degrees] of knee flexion and 5.5[degrees] at 30[degrees] of flexion. (45)

Radiographic Evaluation

Radiographic evaluation may also provide valuable information that should direct concern to a posterior or posterolateral injury. On plain radiography, the position of the knee may reflect a potential injury. Posterior sag may be visible or the overall alignment may be disrupted. Obvious dislocation and subluxations should be observable immediately. Avulsion fractures are not uncommon and may indicate ligamentous injury. Tibial spine or posterior tibial avulsions may indicate cruciate compromise. Avulsion of Gerdy's tubercle may direct one to potential posterolateral instability. An arcuate fracture, or avulsion of the fibular head, should cause the physician to suspect a potential lateral or posterolateral injury. Compression injuries may also be visible, particularly on the tibial plateau. Segond fractures are commonly thought to indicate ACL injury; however, due to the strong lateral capsular insertions, they may also demonstrate posterolateral injury. A widening of the lateral joint space may also be visible. (1) Stress views should be obtained to evaluate for dynamic injury.

Magnetic resonance imaging (MRI) is particularly helpful in the diagnosis of ligamentous injuries about the knee. However, the standard protocols are not ideal for the evaluation of the posterolateral corner. LaPrade and associates (46) described specific protocols for posterolateral corner evaluation, and Yu and coworkers (47) suggested T2-weighted coronal oblique views.

Posterolateral knee injuries often will show bone edema on the anteromedial aspect of the lateral femoral condyle. (48) This pattern of edema was present in all cases of combined PCL and posterolateral corner knee injuries in a study by Ross and colleagues. (48) The size of the fibular styloid fracture may also indicate the severity of injury. Given the various anatomical ligament insertions, the particular area of the fibular head that is avulsed may indicate which ligaments are injured. Small avulsions with medial edema likely represent arcuate or PFL injury. Larger avulsions with diffuse proximal fibular edema correlate with LCL and possibly biceps femoris injuries. (49)

Juhng and associates (50) performed an MRI study looking at associated knee injuries in patients demonstrating the arcuate sign on plain films. A remarkable number of injuries were subsequently discovered on MRI following radiographic observation of an avulsion fracture of the proximal fibula. Of the total number of cases (18 knees; 17 patients), 89% (16 cases) had a cruciate injury and 50% had both ACL and PCL ruptures. Twenty-two percent to 28% had meniscal injuries, while 67% had posterolateral capsule injuries. The popliteus was injured in 33% of patients. This study illustrates the potential for intra-articular pathology when a fibular avulsion fracture is appreciated. It is also notable that the use of ultrasound for musculoskeletal diagnosis is advancing rapidly in the identification of posterolateral corner structures, and while further in vivo research is needed, its accuracy has been confirmed with surgical dissection. (51)

Grading

Various grading systems have been used to describe injuries to the posterolateral corner of the knee. LCL laxity can be referred to as grade I if there is 0 mm to 5 mm of opening compared to the normal side. Grade II injuries demonstrate 6 mm to 10 mm of opening, while grade III injuries have greater than 10 mm of opening and no firm endpoint. The standard nomenclature of athletic injuries has also been applied to the posterolateral corner. Grade I represents minimal tearing of a ligament with no abnormal motion. Grade II injuries have partial tearing with slight or moderate abnormal motion. Grade III injuries demonstrate complete tearing with marked abnormal movement. (2) The various grading systems described make it difficult to compare studies.

Treatment

The treatment of posterolateral corner injury is difficult to assess given the unknown natural history of such injuries. It can be safe to assume that grade I and II injuries should be managed nonoperatively. A brief period of immobilization in full extension, lasting approximately 2 to 4 weeks, can be followed by progressive functional rehabilitation. Progressive range of motion and strengthening exercises should begin afterwards. As strength increases, specific sports programs may ensue. Baker and coworkers (2) showed a full return to pre-injury level in 14 of 31 patients treated with immobilization that was followed by quadriceps strengthening.

When determining operative indications, one must first assess the potential for healing an injury. Using a rabbit model, LaPrade and colleagues (52) examined the potential for healing complete ruptures of the LCL and popliteus tendon. After 12 weeks, a gross and biomechanical analysis demonstrated that only one LCL injury healed and no popliteus tendons healed. This illustrates the lack of potential for healing of grade III posterolateral corner injuries.

Clinically, Kannus (53) has also shown that complete tears have poor functional outcomes. Gait abnormalities and increases in articular pressure have led many surgeons to suggest operative intervention for these injuries. The indications for surgery include symptomatic instability with functional limitations, supplemented by objective physical findings. These may include a 2+ varus opening at 30[degrees] of knee flexion, a positive external rotation recurvatum test, a posterolateral external rotation test, and an increased tibial external rotation test, such as demonstrated by the dial test. (54)

The treatment of acute injuries, traditionally, has demonstrated improved results compared to that of chronic injuries. This discrepancy of outcome is mostly likely influenced by attempts at repair rather than reconstruction. Principles of management include the concurrent treatment of cruciate injuries (55) and assessing the overall mechanical alignment of the knee. Any varus deformity about the knee will place undue stress on the posterolateral aspect of the knee and increase the potential for failure of repair or reconstruction (56) If a varus deformity exists, it should be addressed prior to or concurrently with that of the posterolateral corner. (57)

Treatment may be divided into specific categories or may include a combination of more than one method. Direct repair of the injured structures is the first issue to be addressed. This may or may not include advancement of these structures or augmentation with either autograft or allograft. Reconstruction can be anatomic or nonanatomic. The distinct ligaments may be reconstructed or a nonanatomic construct may be fashioned to provide the same function as the native structures. Reconstruction may use a variety of grafts, including native bone-patellar tendon-bone, hamstrings, or the central aspect of the biceps femoris tendon. Achilles, bone-patellar-bone graft, or alternate tendinous allografts may also be utilized.

A posterolateral reconstruction is usually done through a lateral approach to the knee. The incision begins on the distal lateral thigh and extends toward the region between Gerdy's tubercle and the fibular head. The fascial interval is between the iliotibial band and the short head of the biceps femoris. Terry and LaPrade described a similar skin incision but with the use of three separate fascial incisions and one capsular incision. (58)

The results of direct repair are best when treating avulsions. The knee is kept in about 60[degrees] of flexion with slight internal rotation of the tibia. The results of Baker and associates, (2) with direct repair, showed 85% good subjective results and 77% good objective results. Eighty-five percent of patients returned to their pre-injury level of play; 15% did not.

The issue of timing has to be discussed when dealing with repair of these injuries. Better results with acute over chronic surgical intervention has been demonstrated by Baker and coworkers (34) and Hughston and colleagues. (4) Intervention within the first 3 weeks has been suggested. (59) As chronic injuries have a higher failure rate with repair, reconstruction has been suggested as the more effective treatment. (2)

Augmentation can be used when there is attenuated tissue or the primary repair is tenuous. Slips of the iliotibial band (ITB) or biceps can be used to augment the popliteofibular or popliteus ligaments, respectively. (56,60)

Advancements of the entire posterolateral complex have been described, both proximal and distal. The complex is moved proximally in line with the LCL, fixed to a point anterior to the center of rotation of the knee, and tightened in 30[degrees] of flexion with the tibia in neutral. (4) The results of this procedure have been mixed. DeLee and associates, in 1993, demonstrated 73% good results at 7.5 years with no evidence of degenerative joint disease. (1) Hughston and Jacobsen, (4) in a study of 96 patients using distal anterior advancement, had 85% good objective results, 78% good subjective results, and 80% good functional results. Noyes and Barber-Westin (59) performed proximal posterolateral advancement, in combination with reconstruction of one or both cruciate ligaments. In addition, they fixed the complex to near anatomic origin at 30[degrees] of flexion. Sixty-four percent of patients were fully functional, 27% were partially functional, and 9% were nonfunctional.

Reconstruction techniques use either autograft or allograft. Local autograft donor sites include the central third of the biceps tendon, the iliotibial band, hamstring tendons, and bone-patellar tendon-bone complex. The reconstruction may be either an attempt to anatomically recreate the relevant structures or to recreate the function of the posterolateral corner with alternate structures or techniques. (61,62)

Nonanatomic techniques include the biceps tenodesis and the posterolateral sling procedure. (63) With the biceps tenodesis technique, the biceps tendon is fastened down to the lateral femoral condyle to a point 1 cm anterior to the epicondyle. The fibular insertion and alternate insertions of the biceps tendon are maintained. Clancy and colleagues (64) have demonstrated 90% good results at 2 years with this technique.

The posterolateral sling procedure recreates the function of the posterolateral structures by passing a graft through an anterior-posterior tunnel in the lateral aspect of the proximal tibial plateau. The graft exits anterior to both the lateral gastrocnemius and popliteus and is secured to the LCL origin. Eighty-seven percent improvement in symptoms has been reported. (39)

Various anatomic reconstruction attempts have been described and illustrated. The use of split grafts or multiple grafts with two tunnels attempts to anatomically recreate the function of the LCL, the popliteofibular ligament, and/or the popliteus. Multiple investigators have described excellent techniques for this type of reconstruction. (56,59,61,64,66)

Latimer and associates (63) described a bone-patellar tendon-bone construct for LCL insufficiency in which one aspect of the graft is fixed to the isometric point of the lateral femoral condyle; the other graft end is inserted into the fibular head. The graft is tightened with a valgus load applied while the knee is in 20[degrees] to 30[degrees] of flexion. Interference screws were used to fix the graft. Of 10 patients, none had greater than 5 mm of varus or greater than 5[degrees] of external rotation at 30[degrees]. Five patients returned to their pre-injury level of function, while four remained at one level of function lower.

Combination procedures, including reconstruction of the LCL with plication of the posterolateral structures, have been described as well. Veltri and Warren used a central slip of biceps to reconstruct the LCL. Posterolateral plication was added to prevent excessive external rotation. (56) LCL reconstruction with the Achilles tendon, combined with posterolateral advancement or plication, yielded 76% good or excellent results, with a 10% failure rate. (65)

Comparisons of the two- or three-ligament techniques have been performed. Nao and coworkers (67) examined a reconstruction technique that recreated the LCL and pop-liteofibular ligaments to one that recreated the LCL, PFL and the popliteus. They found that reconstruction of all three ligaments actually led to abnormal kinematics, especially with internal rotation during dynamic testing.

With all of the potential treatment options, it is difficult to determine which yield the best results. This is particularly true when dealing with a more acute injury, as simple repair or plications are still an option. Stannard and colleagues (68) performed an evaluation comparing acute primary repairs to primary reconstructions with a two-tailed technique. Of the 57 patients available for follow-up at 24 to 59 months, 35 patients underwent acute repair. Of the repair group, there were 22 successes, with a failure rate of 37%. The primary reconstruction group demonstrated 20 successes, with only 9% failures. The investigators concluded that primary reconstruction is a better option.

Biceps tenodesis has also been compared to reconstruction. The results of Kanamori and associates (69) showed that reconstructed knees had no difference in tibial external rotation from intact knees, while those that underwent biceps tenodesis had an increase in external rotation of 5.7[degrees]. They suggested that reconstruction reproduces the native knee better than biceps tenodesis.

When examining posterolateral injuries with PCL reconstruction, the results are improved if posterolateral reconstruction is also performed. Knee kinematics are restored to near normal, and forces in the PCL reconstruction are decreased. (51) In addition, external rotation is restored to near normal kinematic patterns. (70) These good results are not the rule. Wang and coworkers (71) showed that for PCL reconstruction combined with LCL advancement and popliteus reconstruction, there was only a 68% satisfactory result; 40% were noted as good, 28% excellent. There was a 32% unsatisfactory rate, with only 44% of knees achieving complete ligamentous stability. Even more alarming is the 44% incidence of degenerative changes, given that the follow-up period was only 2 years to 5 years.

These surgeries are not without complications. Peroneal nerve injuries, vascular injuries, and hamstring weakness have been described. Infection, hardware irritation, arthrofibrosis, and stiffness may also occur. It is important for the surgeon to be aware of potential peroneal nerve displacement. In one study, 16 of 18 patients with biceps avulsions or avulsion fractures of the fibula demonstrated anterior displacement of the peroneal nerve. (72) In that study, the 34 patients with either proximal avulsions, midsubstance disruptions, or distal avulsions without fibular head involvement showed no displacement of the peroneal nerve.

Rehabilitation

Although rehabilitation programs vary, most recommend partial or non-weightbearing in extension for a period of up to 4 weeks in a Bledsoe-type brace. Isometric quadriceps exercises and range of motion are begun as soon as pain permits. Patients are protected from any varus or external rotation stress for a minimum of 2 months. Hamstring strengthening is started after 3 months. Many patients will require 9 months to 12 months of supervised therapy.

Summary

Injuries to the posterolateral corner of the knee remain a difficult entity. The diagnosis requires a high degree of suspicion as well as a thorough knowledge of the functional anatomy of the knee and lower extremity. A detailed clinical examination in various degrees of knee flexion with comparison to the uninjured extremity will often aid in the diagnosis. MRI will help as well although specifically oriented views may be necessary. The treatment of posterolateral corner injuries often requires surgical intervention, particularly if there is a combined ligamentous injury pattern. Recent studies have demonstrated that primary reconstruction may yield better results than repair. Individual clinical scenarios can be evaluated better with knowledge of the various techniques as well as the recent comparative outcomes of those techniques.

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Joshua B. Frank, M.D., Thomas Youm, M.D., Robert J. Meislin, M.D., and Andrew S. Rokito, M.D.

Joshua B. Frank, M.D., was Administrative Chief Resident in the NYU Hospital for Joint Diseases Department of Orthopaedic Surgery, NYU Hospital for Joint Diseases, New York, New York. Thomas Youm, M.D., was an Attending at the NYU Hospital for Joint Diseases, New York, New York. Robert J. Meislin, M.D., is Assistant Professor of Orthopaedic Surgery, New York University School of Medicine, and an Attending in the Shoulder and Elbow and Sports Medicine Services. Andrew S. Rokito, M.D., is Assistant Professor of Orthopaedic Surgery, New York University School of Medicine, and Chief of the Shoulder and Elbow Service, NYU Hospital for Joint Diseases, New York, New York.

Correspondence: Andrew S. Rokito, M.D., Suite 1402, 301 E. 17th Street, NYU Hospital for Joint Diseases, New York, New York 10003.
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