Surgical treatment of posterior cruciate ligament and posterolateral corner injuries. An anatomical, biomechanical and clinical review

The Knee 10 (2003) 311–324

Surgical treatment of posterior cruciate ligament and posterolateral corner injuries. An anatomical, biomechanical and clinical review Pier Paolo Mariania, Roland Beckerb, Jeff Rihnc, Fabrizio Margheritinia,* a

Department of Sports Traumatology, IUSM, University of Motor Sciences, P.zza Lauro de Bosis 15, 00135 Rome, Italy b Department of Orthopaedic Surgery ‘Otto von Guericke’, University of Magdeburg, Magdeburg, Germany c Department of Orthopaedic Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA, USA Received 1 September 2002; received in revised form 1 October 2002; accepted 16 October 2002

Abstract The posterior cruciate ligament has become an increasingly popular subject of orthopaedic research and debate. While biomechanical studies have shown its role as major stabilizer of the knee, clinical studies have shown its increasing incidence. Furthermore, injuries to posterolateral structures are frequently encountered and failure to recognize and treat this associated injury may lead to stretching or failure of the cruciate reconstruction. Surgical reconstruction of isolatedycombined injuries is now more effective than before and different technical options are now available for the surgeon, even if much work remains ahead of us as we try to understand how to successfully treat these complex knee injuries. 䊚 2002 Elsevier Science B.V. All rights reserved. Keywords: Posterior cruciate ligament; Posterolateral corner; Reconstruction; Arthroscopy; Biomechanics

1. Introduction The posterior cruciate ligament (PCL) has become an increasingly popular subject of orthopaedic research and debate. Despite recent advances in our understanding of the anatomy and biomechanics of the PCL and the effects of PCL injury on knee function, injury of this ligament remains a challenging problem. For many years, PCL injury had been considered a rare and relatively clinically benign event. Recently, however, the incidence of injury has been reported to be higher than previously believed w1x, and studies have shown that chronic PCL-deficiency is associated with poor clinical outcomes w2–4x. Recent clinical and basic science research has led to the development of new techniques for PCL reconstruction. No single technique, however, has proven to be efficacious in restoring knee stability and altering the natural history of PCL-deficiency. Furthermore, an increased awareness of combined posterior cruciate and posterolateral corner (PLC) injuries has *Corresponding author. Tel.: q39-6-35455231; fax: q39-635452530. E-mail address: [email protected] (F. Margheritini).

raised new concerns in the orthopaedic community. This article is intended to provide an up-to-date review of the basic and clinical science of the PCL and posterolateral structures as well as the current surgical techniques used to treat injury of these structures. 2. Anatomy of the PCL and PLC The PCL arises from the posterior tibia 10 mm below the joint line and extends anteromedially to the lateral surface of the medial femoral condyle. Anatomically, it is considered an intraarticular but extrasynovial ligament. Synovium that is reflected from the posterior capsule surrounds the medial, lateral, and anterior border of the ligament w5,6x. The average length of the PCL is between 32 and 38 mm with a cross-sectional area of 31.2 mm2 at its midsubstance level, which is 1.5 times that of the anterior cruciate ligament (ACL) crosssectional area w5,7,8x. The femoral and tibial insertion sites of the PCL are approximately three times larger than the cross-sectional area of the midsubstance of the ligament w7,9x. The femoral attachment is semicircular and horizontal in direction, with a footprint of 32 mm (Fig. 1) in length that terminates 3 mm proximal to the

0968-0160/03/$ - see front matter 䊚 2002 Elsevier Science B.V. All rights reserved. doi:10.1016/S0968-0160Ž02.00141-2

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Fig. 1. Anatomical view of a right knee. Note the wide insertion of the PCL (as indicated) on the medial femoral condyle (courtesy of ` Dr Pau Golano).

articular cartilage margin of the femoral condyle w6x. The tibial insertion is located within a depression between the posterior aspect of the medial and lateral plateaus, approximately 1 cm distal to the joint line. It has an average width of 13 mm w5x. Hefzy et al. observed that very few fibers of the PCL behave isometrically, with most of the fibers lengthening upon knee flexion w10x. The large ligamentous insertion sites and the lack of isometry within the fibers of the PCL complicates the task of designing a PCL reconstruction technique that adequately recreates the anatomical and biomechanical properties of the intact PCL. The fibers of the PCL are usually reported as two separate bundles: the anterolateral (AL) and the posteromedial (PM) bundles w6,8x. The distinct insertion sites of these two bundles on the tibia and femur are approximately equal in size w9x. The AL bundle is two times larger in cross-sectional area than the PM bundle w6,8,11x. Functionally, the two components have different tensioning patterns that are dependent on the degree of knee flexion. During passive flexion and extension of the knee the AL bundle is more taught in flexion and lax in extension, conversely, the PM bundle is more taught in extension and lax in flexion w5,6x. Recently,

the PCL architecture has been described as four fiber regions based on their orientation and function at different degrees of knee flexion w12x. Further study is needed to evaluate the biomechanical and clinical implications of this more recent anatomic description. In addition to the PCL, the meniscofemoral ligaments (MFLs) of Humphrey (anterior) and of Wrisberg (posterior) comprise the PCL complex. They originate from the posterior horn of the lateral meniscus, run adjacent to the PCL, and insert anterior and posterior to the PCL on the medial femoral condyle w13x. The importance of the MFLs has not been fully characterized. Described as the ‘third cruciate ligament’ at the beginning of the 19th century, it has recently been suggested that the MFLs contribute to the anterior–posterior and rotatory stability of the knee w8x. No studies exist, however, that clearly define their biomechanical role. The middle geniculate artery provides the majority of the blood supply to the PCL, giving off branches to the synovial tissue that surrounds the ligament. An avascular portion in the central part of the middle-third of the PCL has recently been described, suggesting that proximal and distal lesions of the PCL have more potential for healing than midsubstance tears w14x. The PLC of the knee has a complex and variable anatomy, making effective surgical reconstruction a challenge. It consists of a complex system of stabilizers that provide posterolateral stability to the knee: among those we include the lateral collateral ligament (LCL), the arcuate ligament complex, the fabellofibular ligament, the posterior horn of the lateral meniscus, and the lateral part of the posterior capsule. As part of muscle structure we also include the popliteus complex, the biceps tendon, and the iliotibial tract w15–21x. Of these structures, the LCL and the popliteus complex are considered to be primary stabilizers w16,22x. Specifically, the popliteus complex is one of the key factors providing stability to the posterolateral aspect of the knee. It includes the popliteofibular ligament, the popliteotibial fascicles, and the popliteomeniscal fascicles, all of which arise from the popliteus tendon and insert onto fibula, the tibia, and the meniscus, respectively. The popliteus muscle–tendon unit originates on the PM surface of the proximal tibia and inserts in the popliteal groove of the lateral surface of the lateral femoral condyle w19x. Maynard et al. w21x report that, the popliteofibular ligament is the most significant in providing posterolateral stability, while electromyographic studies have shown that the muscle–tendon unit serves mainly to internally rotate the tibia w23,24x. 3. Biomechanics of the PCL and PLC Biomechanical studies have shown that the PCL is a major stabilizer of the knee. It has a primary function of preventing posterior tibial displacement w25–29x, and

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a secondary role in limiting external, varus and valgus rotations w27,30x. Prietto et al. reported that the femur– PCL–tibia complex has a stiffness and an ultimate tensile load that is slightly higher than that of the ACL w31x. Of the two bundles that comprise the PCL, the AL bundle of the PCL is larger and stiffer than the PM bundle w8,11x. Harner et al. showed the linear stiffness of the AL bundle (120"37 N m) to be 2.1 times that of the PM bundle and 2.5 times that of the MFL, and the ultimate load of the AL bundle (1120"362 N m) to be 2.7 times that of the PM bundle and 3.8 times that of the MFL w8x. Several biomechanical cutting studies have demonstrated that isolated sectioning of the PCL results in increased posterior tibial translation under a posterior tibial load, with maximal translation occurring at 908 of knee flexion (values ranging from 1 to 5 mm at 08 flexion to 11–20 mm at 908) w27–29,32,33x. Furthermore, results suggest that a biomechanical interaction exists between the PCL and the posterolateral structures in providing stability to the knee w27–29x. Sectioning both the PCL and posterolateral structures increases posterior tibial translation more than sectioning either structure alone w27,29x. The posterolateral structures play a primary role in resisting excessive varus and external rotational forces w16,22,28,34,35x. Of the components of the PLC, the LCL is the primary structure that resists varus rotation at all positions of knee flexion, while the popliteus complex and the posterolateral part of the capsule provide primary restraint against external tibial rotation. Gollehon et al. w28x and Grood et al. w27x showed that combined sectioning of the LCL and the deeper ligament complex of the posterolateral knee causes increased varus rotation. When both the PCL and posterolateral structures are sectioned, varus and external tibial laxity is increased significantly compared with sectioning of either structure alone w27,28x. It is evident that the posterolateral structures play a secondary role in restricting posterior tibial translation, offering the most restraint between 0 and 308 of knee flexion. Recent evaluation of in situ forces of various knee structures have enhanced our understanding of PCL and PLC injury. In accordance with cutting studies that show the PCL offers greatest posterior restraint in the flexed knee, studies have found that in situ force in the PCL increases with knee flexion w36–39x. Fox et al. w37x report that no significant differences between the in situ forces of the AL and PM bundles exist, suggesting that both bundles are important to knee stability and should be considered while planning PCL reconstruction. These data are in contrast with data presented by different authors, who found that in addition to having a larger cross-sectional area, the AL bundle is made of stronger material than that of the PM bundle, which explains the higher failure loads of the AL bundle w11x. An isolated

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section of the PCL has been shown to cause a significant increase in the in situ force of the posterolateral structures at all knee flexion angles w40x and an increase in the joint contact forces in medial and patellofemoral compartments w41,42x. Furthermore, injuries to the PLC increases the in situ force of the intact PCL, and failure to reconstruct the posterolateral structures in the setting of a combined PCLyPLC injury places increased stress on the PCL graft. w43,44x. This increased graft stress likely contributes to graft elongation andyor early graft failure and supports reconstructing of both the posterolateral structures and PCL in such combined injuries. 4. Incidence and clinical evaluation of PCL injuries The incidence of PCL injuries has been increasing over the past several years. This increased incidence is likely the result of the heightened awareness and improved diagnostic techniques. PCL injuries have been reported to account for 3 w45x to 37% w1x of all ligamentous knee injuries in an outpatient setting and a traumatic setting, respectively. Up to 95% of PCL injuries involve additional structures of the knee. It has been reported in the acute setting that up to 60% of PCL injuries also involve the PLC w1x, 12% have associated chondral defects, and 27% have associated meniscal tears w45,46x. The most common mechanism of PCL injury is a posteriorly directed force applied to the proximal tibia, as is seen in car accidents (the classic ‘dashboard injury’) but hyperflexion w47,48x and hyperextension have also been described in the literature as mechanisms that commonly result in sports related PCL injury w49x. A proper evaluation of the PCL and posterolateral structures begins with a thorough history of the initial injury. The mechanism of injury can suggest an isolated versus a combined injury pattern. An isolated PCL injury knee does not usually cause specific symptomatic complaints. A large joint effusion, significant loss of motion, instability, and severe pain should raise concerns for injuries to additional knee structures including nerves and vessels. On physical examination, the patient should be evaluated for malalignment, gait abnormalities, joint effusion, and loss of motion w50x. Chronic PCLyPLC combined injury often results in significant varus malalignment and an associated varus thrust with ambulation. The most accurate test for detecting PCL injury is the posterior drawer test w51x. This test can be divided in three grades according to the degree of posterior translation: a grade I injury is represented by posterior translation between 1 and 5 mm, grade II between 5 and 10 mm (with the anterior border of the tibial plateau lying flush with the femoral condyles), and grade III greater than 10 mm (with the anterior border of the tibial plateau lying posterior to the femoral condyles).

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While the posterior drawer remains the starting point of any examination, several adjunctive tests have been described for quantifying PCL deficiency, such as the posterior Lachman, the prone drawer test, the dynamic posterior shift test, the quadriceps active test, and the Godfrey’s test (posterior sag test) w52–54x. A small increase in posterior translation at 308 and not at 908 may indicate a PLC injury. Two tests can reliably be used to further evaluate the knee for PLC injuries: the reversed pivot shift test w55x and the tibial external rotation test w27,28x. For the reversed pivot shift test, the patient is positioned supine on the examination table and the knee is initially held in 908 of flexion. The knee is then externally rotated and passively extended. If an injury of the PLC is present, a shift occurs at 20–308 of flexion as the posteriorly subluxated lateral tibia plateau is reduced anteriorly. The tibial external rotation test is performed at 30 and 908 of knee flexion with the patient supine or prone. An increased rotation at 308 but not at 908 indicates an isolated PLC injury, while an increased angle at both 30 and 908 indicates a combined PLCyPCL injury. Much information regarding PCL injury can be obtained from imaging studies, including stress radiographs and magnetic resonance imaging (MRI). Stress radiographs show the amount of posterior subluxation of the tibial plateau w56–59x. MRI has been shown to be extremely effective in confirming the diagnosis of acute PCL injury, with a reported sensitivity and specificity of 100% w60x. In chronic grade I and II injuries, however, the PCL may appear normal on MRI and for this reason MRI is not the study of choice in chronic phase. 5. Natural history The natural history of PCL injuries is the subject of continual debate. For several decades it has been suggested that isolated PCL injuries have good outcomes with a conservative treatment w47,61,62x. Parolie and Bergfeld w62x found that 80% of the patients were subjectively satisfied with their injured knees and that 68% had returned to their pre-injury level of athletic performance following a conservative course of treatment. Recent studies, however, have demonstrated less favourable outcomes, with patients experiencing significant symptoms and functional limitations with chronic PCL-deficiency w2–4x. Keller et al. w4x, in a study looking at the outcomes of nonoperative treatment of PCL injury, reported that 65% of their patients treated conservatively were limited in their activity, with 90% reporting knee pain during activity, 43% complaining of problems while walking, and 45% reporting problems with knee swelling. Furthermore, several studies have demonstrated the development of medial compartment and patellofemoral degenerative changes and an

increased risk of meniscal tears with chronic PCL deficiency w3,46,63x. Shelbourne in 1999 w64x reported the outcome of 133 patients with an acute, isolated nonoperative treated PCL injuries. Data collected at an average follow-up of 5.4 years led to the conclusion that athletically active individuals, with acute isolated PCL injuries (-10 mm of posterior displacement) treated nonoperatively can achieve a good level of function without experiencing specifically clinical symptoms. 6. Surgical management Findings that PCL deficiency can have detrimental long-term effects on knee function have raised concerns and debate regarding appropriate management. The approach to treatment of PCL injuries should take into account the severity of the knee injury, timing, symptoms and activity level. A consensus regarding the indications for PCL reconstruction has not been reached. Most authors agree that acute repair of avulsion fractures of the PCL provides the most favourable outcome w65– 68x. Furthermore, combined injuries of the PCL (involving the posterolateral structures, ACL andyor medial collateral ligament, MCL) should be treated surgically. Treatment of the isolated PCL injury is less straightforward. Treatment decisions are made on an individual basis, taking into account the severity and timing of injury, development of symptoms (pain and instability) and activity level. In general, isolated grade III PCL injuries with more than 10 mm of posterior translation on posterior drawer examination are treated surgically in active patients that do not improve with physical therapy and in patients that develop pain, instability, or evidence of chondrosis upon follow-up examination. A variety of surgical techniques have been proposed but PCL reconstruction has not achieved the clinical success that ACL reconstruction has in restoring knee stability and function w69–77x. 6.1. Timing of the operation The timing of surgical treatment depends on the nature of the PCL injury and the presence of associated ligamentous injuries. The most appropriate time to reconstruct the PCL is related to the capacity of the injured ligament to heal with conservative treatment. A recent study has shown that complete disruptions of the PCL and the MFLs are less likely to heal and regain function with time w78x. Early reconstruction of these serious injuries provides the patient with improved function without delaying surgery for a course of conservative treatment. Combined PCLyPLC injuries experience the most favourable clinical outcomes when treated surgically. Surgical treatment of combined injuries involving severe

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disruption of the MCL is delayed to give the MCL a chance to heal on its own. In most cases, the medial structures have a good healing response following a conservative course of treatment w79,80x. On the opposite the clinical outcome of primary repair of the acutely injured PLC has been shown to be superior to that of delayed reconstruction of the injured structures w81x.

regards to the method of tibial attachment of the PCL graft, PCL reconstruction can be divided into the anatomic fixation (inlay) technique and the trans-tibial tunnel technique. Furthermore, the type of PCL reconstruction can be described as a single- or double-bundle technique, according graft construct that is chosen for the reconstruction.

6.2. Graft selection

7.1. Trans-tibial tunnel technique. Single-bundle and double-bundle techniques

Graft types can be divided into autografts, allografts, and synthetic grafts. In choosing a graft, consideration should be given to graft length and cross-sectional area and bony fixation at the ends of the graft. Autografts that are adequate for PCL reconstruction include the patellar tendon w63x, the hamstring tendons w82x and the quadriceps tendon w72,83x. The patellar tendon is the most commonly used graft for PCL reconstruction: with its proximal and distal bone plugs, this graft allows for easy, rigid fixation. The hamstring tendons, although associated with relatively little donor site morbidity w84x provide inferior fixation than grafts that incorporate a bone plug, while the quadriceps tendon has been popularized due to the large graft size and the availability of tissue w72x. The large cross-sectional area and the generous length of the quadriceps tendon graft allow for close approximation of the native PCL and minimize graft–tunnel size mismatch. The allograft is an excellent alternative for use in PCL reconstruction, especially in complex ligament injuries, revision surgery, or in patients with generalized ligamentous laxity w85–87x. The allograft Achilles tendon is a popular graft choice for PCL reconstruction because of its generous cross-sectional area and calcaneal bone plug that provides rigid bony fixation. Advantages of using an allograft include reduced donor site morbidity and surgical time, as well as the ability to use multiple grafts when treating combined injury or performing a double-bundle reconstruction even if no advantages have been reported by some authors when used in alternative to autografts w88x. Furthermore, concerns exist, regarding the increased risk of disease transmission, the delay in the remodelling process and the cost. Because of their increased stiffness, synthetic grafts do not adequately simulate the biomechanical properties of ligaments and tendons. The poor outcomes achieved using synthetic grafts for ACL reconstruction has discouraged their use in PCL reconstruction. Attachment site problems, cyclic wear, and fatigue failure have reduced the indications for using such grafts in knee ligament reconstructions. 7. Surgical techniques for PCL reconstruction PCL reconstruction techniques can be categorized as arthroscopic, arthroscopically assisted, or open. In

The trans-tibial technique has been popularized by Clancy et al. w63x. It is based on the use of a single tibial tunnel that is drilled from the anteromedial aspect of the proximal tibia to the posterior aspect of the proximal tibia at the site of PCL insertion. Even though it was originally described as an open procedure, the technique is now routinely performed arthroscopically. Following an exam under anaesthesia, the patient is positioned using well-padded leg holders and the tourniquet is placed on the proximal thigh of the injured leg. Traditional anterior arthroscopy is performed to confirm injury of the PCL and address any associated intraarticular pathology. A PM portal is placed in order to allow visualization of the tibial insertion site and to protect the neurovascular vessels from iatrogenic injuries. The PM portal is made using a 1.5-cm incision that starts at the PM border of the proximal tibia (Fig. 2a and b). Transillumination with the arthroscope while making the PM portal helps avoid injury to the saphenous nerve and vein w81x. Findings during anterior arthroscopy that support PCL injury include the following: apparent laxity of the ACL (‘psuedolaxity’) that results from posterior subluxation of the tibia in a PCLdeficient knee; posterior displacement of the medial femoral condyle in relation to the medical meniscus; and, in the setting of chronic PCL-deficiency, chondrosis of the medial and patellofemoral compartments w89x. The tibial stump of the PCL can be visualized using a 708 scope either in the AL or PM portal. In preparation for the drilling of the tibial tunnel, a 2–3 cm vertical skin incision is made 4 cm distal to the joint line and slightly medial to the tibial tubercle. A 1.8-mm guide wire is started 4 cm distal to the joint line and 2 cm medial to the tibial tubercle or directly thorough the bone trench w71x coming out after harvesting the bone– patellar–tendon–bone (BPTB) and placed trans-tibially at an angle of ;508 in reference to the posterior cortical bone of the tibia. It is important to maintain this range of inclination to minimize the sharp angle produced by passing the graft around the posterior edge of the tibia. This sharp bend has been described as ‘the killer turn’ and it is thought to cause increased graft stresses and wear w90x. At this time, fluoroscopy can be used for checking the position of the guide wire. This, in the lateral view, should be placed at the level of the proximal

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Fig. 2. External (a) and arthroscopic view (b) of the PM access in a right knee. The arthroscopic view shows a 4.5 mm cannula inserted through the access to facilitate the instrument passage.

tibia–fibula joint line and should exit the posterior tibial cortex approximately 1 cm below the tibial plateau. The PM portal can be used to visualize the site of tibial PCL insertion and avoid over drilling that can cause injury to the neurovascular structures of the popliteal fossa. Additionally, a posterolateral portal can be easily and safely prepared. This ‘trans-septal portal’ w91x allows a more complete view of the posterior compartment of the knee. Drilling the posterior cortex of the tibia should be performed carefully to avoid perforation of the posterior capsule. MRI studies have shown an average safe distance of 7.6 mm in the axial plane and 7.2 mm in the sagittal plane between the posterior edge of the PCL and the anterior margin of the popliteal artery w92x. This safe distance may be an overestimation, however, for this study was performed on healthy knees and did not account for the fibrosis and soft tissue retraction that is often associated with chronic PCL tears. The femoral site of attachment can be prepared either as single or a double tunnel. The single-bundle technique is designed to simulate the AL bundle of the PCL. The rationale for utilizing this procedure is threefold. First, the AL bundle has been shown to be the stronger and stiffer of the two bundles of the PCL w8,11x. Secondly, the AL bundle is taught in knee flexion and functionally

contributes more than the PM bundle at 908 of knee flexion, the flexion angle at which the PCL has been shown to offer maximal restraint to posterior tibial displacement w27,28x. Finally, the injured PCL often contains intact PM or meniscofemoral fibers that can serve as a natural augmentation for the single AL bundle. It has been shown that the location of the femoral tunnel has more impact on the ability of the reconstruction to restore intact knee kinematics than does the position of tibial fixation w93–97x. According to Morgan et al. w98x, the femoral tunnel used for reconstructing the AL bundle should be placed 10 mm posterior to the articular cartilage of the medial femoral condyle and 13 mm inferior to the articular cartilage of the medial intercondylar roof, at the footprint of the AL bundle of the native PCL (Fig. 3). The double-bundle technique has recently been reported to be more efficacious in simulating the tension patterns of the two bundles of the native PCL and restoring normal knee biomechanics w5,8,11,30,33,99x. Harner et al., comparing the single- and double-bundle PCL reconstruction techniques in the laboratory reported that the double-bundle reconstruction restored posterior tibial laxity to that of the intact knee and restored the in situ force of the PCL more closely to the intact knee than did the single-bundle reconstruction, under a pos-

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Fig. 3. Arthroscopic view of the K-wire exit at the internal surface of the medial femoral condyle approximately 8–10 mm posterior to the anterior cartilage border. The use of a marked probe helps in controlling the position.

terior load of 134 N w33x. Two divergent femoral tunnels are required for the double-bundle reconstruction. A quantitative study of the insertion sites of the cruciate ligaments reported a relatively large PCL femoral insertion area of 128 mm2, providing enough surface area to accommodate two tunnels w9x. The femoral tunnel for the AL graft is placed according to the above description. The PM tunnel is placed within the PCL footprint more inferior to and slightly deeper in the intercondylar notch than the AL tunnel (Fig. 6). A bone bridge greater than 5 mm in width should be preserved to avoid collapse of the tunnel bridge. Recently Mannor et al. w100x showed that placing the PM bundle distally helps in controlling the posterior displacement within the all range of flexion–extension (Fig. 4). The femoral tunnel(s) can be drilled using either an inside-out or outside-in technique. Using the inside-out technique, the K-wire is introduced through the anteromedial portal while the knee is held in 80–908 of flexion w77,101x. For the outside-in technique, an additional incision at the lateral femoral condyle is needed for positioning of the femoral guiding device. In order to reduce the risk of osteonecrosis, the tunnels should not be drilled through the subchondral bone of the femoral condyle w102x. According to the chosen tendon, the graft is pulled through the tibial tunnel, over the posterior aspect of the tibial plateau, and into the femoral tunnel using a looped 18-gauge wire or graft passer. The bone block is advanced in the tibial tunnel until the proximal edge is flush with the posterior cortex of the proximal tibia to minimize graft length and graft bending within the

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tunnel w103x. A blunt trocar introduced through the PM portal can be helpful in assisting the progression of the bone block and the tendon w104x. When using an Achilles tendon allograft, the bone block can be fixed either on the femoral or tibial side. In the double-bundle technique, two separate grafts or a split graft are passed through the tibial tunnel and then fixed in separate femoral tunnels. Important considerations before final fixation of the graft include preconditioning and tensioning conditions. The graft(s) should be preconditioned to minimize elongation following final fixation. This is accomplished by passively moving the knee through its full range of motion several times while applying tension (10 lb) to the unfixed end of the graft. During fixation of the AL graft (for both the single- and double-bundle techniques), the knee is held in 70–908 of flexion and an anterior drawer force is applied to recover the normal step-off between the medial femoral condyle and the medial tibial plateau w105x. Approximately 10–20 lb of tension is applied to the unfixed end of the graft and a posterior drawer test is performed to confirm restoration of posterior knee stability. Final fixation is achieved using one of many options for graft fixation. The PM graft, in the double-bundle reconstruction, is fixed at 15–208 of knee flexion with an applied anterior drawer and approximately 10–20 lb of tension w33x. The method of fixation will vary depending on graft selection and on experience and surgeon’s preference. An interference screw 20–25 mm in length with a diameter similar to that of the bone tunnel provides rigid

Fig. 4. Mid-shaft section of a left knee showing the position of the two bundles when performing the double-bundle reconstruction. According to Mannor et al. a more distally (b) placed PM bundle should produce less posterior translation than a proximally (a) one placed.

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fixation for the bone blockygraft complex. Soft tissue fixation can be achieved with a variety of techniques including a screw and spiked washer, an Endobutton, a suture post, or a soft tissue (bioabsorbable) interference screw. The femoral bone bridge, in the case of a doublebundle reconstruction, is particularly susceptible to fracture during graft fixation. In this specific case, extraarticular fixation using Ethibond sutures and an Endobutton or a suture post may be a safer option than the interference screw. 7.2. Inlay technique The inlay technique for PCL reconstruction was first described in Europe by Thomann and Gaechter in 1994 w106x and in the US 1 year later by Berg w90x. This technique provides anatomic reconstruction of the AL bundle of the PCL. First described as a single-tunnel technique, modifications can be made using split grafts that provide a double-bundle reconstruction w107x. The tibial inlay technique requires an open posterior approach to the knee. It involves direct fixation of a bone plugygraft complex (patella tendon, Achilles tendon) to a unicortical bone trough at the anatomic site of tibial PCL insertion. This fixation avoids the sharp angle of the graft observed at the proximal margin of tibial tunnel in the more traditional trans-tibial technique. It has been proposed that this ‘killer turn’ generates increased graft stress and friction that may contribute to graft elongation or failure after initial fixation w90,108x. For the inlay technique, the patient is either positioned in the lateral decubitus position (injured leg up) for the entire procedure or requires intraoperative repositioning from a supine to a prone position. These two options for positioning allow access to the anterior and posterior aspects of the knee. In the lateral decubitus position, the hip is abducted and externally rotated 458 and the knee is flexed to 908 during anterior arthroscopy, graft harvest, and arthroscopic drilling of the femoral tunnel. Following anterior arthroscopy, the knee must be fully extended and slightly abducted to achieve adequate exposure for the posterior approach. If anterior arthroscopy is performed while the patient is supine, the patient must be turned prone intraoperatively to achieve adequate exposure for the posterior approach to the knee. Femoral tunnel is drilled during anterior arthroscopy as described above. A looped 18-gauge wire or graft passer, that is later used to pass the graft, is then placed through the femoral tunnel into the joint. The injured leg of the patient is then repositioned in preparation for the posterior approach. The posterior approach used in the tibial inlay technique involves an oblique incision lateral to the medial gastrocnemius muscle as described by Burks and Schaffer w109x. The deep fascia of the medial gastrocnemius muscle is incised vertically, parallel to the direction of

the muscle fibers. Attention must be paid to the sural nerve, which runs between the medial head of the gastrocnemius muscle and the semimembranosus tendon. The head of the medial gastrocnemius muscle is incised and retracted laterally along with the neurovascular structures of the popliteal region. A vertical incision is made in the posterior capsule to expose the site of tibial PCL insertion. A unicortical bone block is removed at the tibial PCL insertion site to create a trough that will accommodate the bone plug of the graft. The bone plug of the graft is placed in the trough and fixed with a 6.5mm cancellous screw and washer w90,109x. Using the Ethibond sutures attached to the tendinous end of the graft and the prepositioned looped 18-gauge wire, the graft is passed through the femoral tunnel and fixed using the AL bundle tensioning pattern described above w105x. It remains unclear whether the anatomic fixation of the PCL graft achieved by the inlay technique is more efficacious than the traditional trans-tibial technique in restoring normal knee biomechanics. Recently, in a cadaveric study, Bergfeld et al. w108x compared the ability of the inlay and trans-tibial techniques to restore posterior tibial laxity. These authors reported that the tibial inlay technique results in less posterior translation and less graft degradation when compared to the transtibial tunnel technique for PCL reconstruction. More recent biomechanical studies, however, have failed to show significant difference in knee stability when comparing the inlay technique to the traditional trans-tibial technique w110,111x. 7.3. Osteotomy The role of osteotomies in increasing the tibial slope and consequently reducing the posterior tibial translation has been recently investigated. Biomechanical studies have shown that a 5 mm anterior open wedge osteotomy can reduce the posterior translation up to 2.6 mm w112,113x, while clinical studies have confirmed the kinematic path w114x. Further investigations need to be performed in order to assess the long-term outcomes and to look over the increase of force, which can be seen in the other ligamentous structures. 7.4. Repair of bony PCL avulsion Torisu w115x reported that early repair of bony avulsion of the PCL provides better clinical outcome than delayed fixation. Surgical fixation of the avulsed PCL is usually performed through an open posterior approach with the patient in the prone position. According to Trickey w116x, the posterior approach does not allow full evaluation of the knee joint but offers the best exposure to the tibial insertion site of the PCL.

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biomechanical studies exist, however, that compare the efficacy of these different surgical techniques. 8.1. Treatment of acute injuries of the PLC

Fig. 5. Artrhroscopic view of the external compartment in a combined PCLyPLC instability. Note the wide opening of the compartment measured with a special probe (Atlantech Medical Devices, Harrogate, UK).

An arthroscopic technique for repairing the avulsed PCL has been described by Deehan and Pinczewski w117x. This approach uses anteromedial, AL, PM and posterolateral portals. Under arthroscopic visualization, the PCL stump is first debrided, then three K-wires are passed trans-tibially towards the insertion site of the PCL. The avulsed ligamentybony fragment is reduced, and the K-wires are advanced through the bony fragment. Finally, using a needle driver, the ends of the Kwires are turned into a U-shape to ensure that the reduction is maintained. A study by Seitz et al. w118x compared the clinical outcome of this K-wire fixation technique to that of the open technique involving screw fixation. Twenty-six patients were followed up after an average of 10.5 years without any clinical difference detected. 8. Surgical techniques for PLC injuries Isolated PCL injuries are much less common than combined injuries. Ninety-five percent of PCL injuries have associated ligamentous injuries in the same knee and up to 60% of PCL injuries are associated with an injury of the PLC w119x (Fig. 5). Treatment of these associated injuries is imperative in order to achieve good clinical results. Failure to do this produces increasing force in the graft with early failure w44,120x. Conservative treatment of multiligament injuries has experienced poor clinical outcome w61x. Combined PCL injuries, with involvement of the ACL, LCL, MCL or posterolateral structures, generally require complex surgical management w121–126x. Surgical options for posterolateral injuries include primary repair, advancement, recession, augmentation and reconstruction. No clinical or

Acute surgical treatment of PLC injuries has achieved better clinical results than reconstruction of chronic injuries w127–130x. Primary anatomic repair of the posterolateral structures in an acute setting (-3 weeks after injury) offers the best surgical outcome w129,131,132x. Noyes and Barber-Westin described the use a straight lateral incision approximately 12–15 cm in length over the lateral joint line that is extended distally and proximally to allow exposure of the fibular head and the femoral site of LCL attachment, respectively w107x. During the exposure, it is important to evaluate the main components of the PLC, including the iliotibial tract, peroneal nerve, biceps femoris tendon, LCL, and the popliteus complex. Direct suture repair of the injured structures is performed from deep to superficial. Severe injuries that are not amenable to primary repair may require augmentation. Many options exist for augmenting the structures of the PLC, including use of the iliotibial tract, the biceps femoris tendon, the hamstring tendon, or an allograft w132,133x. 8.2. Treatment of chronic injuries of the PLC Because of excessive scar tissue, laxity of secondary restraints, and limb malalignment, primary repair of chronic PLC injuries has not proven successful in restoring knee stability. Reconstruction of the posterolateral structures is a better surgical option. The goals of surgical treatment are to restore intact knee kinematics and reduce the likelihood of progressive degenerative arthritis. Numerous techniques for posterolateral reconstruction have been described in Refs. w126,133–137x. For surgical treatment of chronic PLC injuries, w124x recommended the transfer of the biceps femoris tendon to the lateral femoral condyle, leaving its insertion on the fibular head intact. Tenodesis of the biceps femoris tendon is thought to simulate that native LCL w136x. During this procedure, the biceps tendon must be dissected free from the lateral gastrocnemius muscle before it can be transected and fixed to the femur. The biceps tendon is separated from its muscle belly, passed underneath the iliotibial band, and attached to the lateral femoral epicondyle. Temporary fixation is achieved using a K-wire until the isometric point of the new tendinous construct is determined. A 6.5-mm cancellous screw and a spiked washer are used for permanent fixation. Clancy and Terry w138x followed 39 patients with chronic posterolateral instability for an average of 32 months after having this procedure. The authors found that 77% of the patients enrolled in the study had no restrictions in everyday activities. Furthermore, 54%

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of the patients were able to return to their previous level of athletic activity. Bousquet et al. w139x describe a similar technique that uses the posterior half of the biceps tendon to reconstruct the PLC. The biceps tendon is divided longitudinally, and a 6-mm wide strip of tendon is dissected proximal to distal, leaving the distal end of the tendon attached to the fibular head. The strip of tendon is passed underneath the remaining biceps tendon and the iliotibial band is fixed to the lateral femoral epicondyle. Noyes and Barber-Westin w107x recommended proximal advancement of the posterolateral complex in cases of chronic posterolateral instability in which lax but intact posterolateral structures can be identified. It is essential that the structures are of adequate thickness: the LCL should be greater than 5-mm width and the posterolateral structures greater than 3-mm thick to be functional following the advancement procedure. The advancement of tissue with excessive scarring and poor collagen content may lead to early failure of the procedure. This technique involves advancement of the lax ligaments (LCL and posterolateral structures) proximally along the line of their native attachment sites. The tissue is advanced at 308 of knee flexion and staple fixation is achieved at the original sites of anatomic. The authors reported on a series of 21 combined injury patients following proximal advancement of the posterolateral structures and PCL reconstruction w134x. They found at an average of 42 months postoperatively that the posterolateral advancement was fully functional in 14 knees (64%) and partially functional in 6 knees (27%). In more severe chronic injuries, in which inadequate tissues are present for advancement, they recommended primary reconstruction of the LCL and popliteus–arcuate complex using a 10 mm BPTB autograft and twostrand hamstring (semitendinosus and gracilis) tendon autograft, respectively. In reconstructing the LCL, the BPTB graft is fixed distally in a fibular head tunnel using two small fragment screws and proximally in a femoral tunnel at the anatomic site of LCL attachment using an interference screw. The doubled-over semitendinosus–gracilis graft is fixed proximally at the femoral site of popliteus tendon attachment using an Endobutton. Distally, the two strands of the semitendinosus–gracilis graft are passed and fixed separately, one through a tibial tunnel and one through a fibular tunnel. Another technique using the semitendinosus tendon top reconstruct the PLC has been described by Larson and Metcalf w126x. The graft can be passed through the fibular head and routed to the lateral femoral condyle achieving a figure-of-eight configuration. In an effort to approximate the popliteofibular ligament, Larson and Metcalf utilize the posterior aspect of the fibular head for the distal site of graft attachment. When no varus laxity is present the technique can be modified by

passing the both strands of the graft within the fibular head and fixing them without twisting the graft into a figure-of-eight configuration. Latimer et al. w137x described the use of a 9-mm BPTB allograft secured with interference screws to reconstruct the LCL in cases of PLC injuries. These authors performed a retrospective study of 10 patients with combined cruciate ligament injuries and posterolateral instability. The LCL was reconstructed using a BPTB allograft and the cruciate ligaments were reconstructed using allograft or autograft material. At an average of 28 months after surgery, excessive external rotation at 308 of knee flexion was corrected in all but one knee. Furthermore, six patients had no varus laxity and four patients had 1q varus laxity at 308 of knee flexion. The authors concluded that the relatively large graft (when compared to the native LCL) may offer additional restraint that is provided by the native popliteofibular ligament in the intact knee. Veltri and Warren w16x recommended anatomic reconstruction of these structures to achieve the best results in the operative treatment of chronic posterolateral instability. The injured LCL can be anatomically reconstructed using a central section of the biceps femoris tendon. In PLC injuries that involve both the popliteotibial and popliteofibular components of the popliteus complex, reconstruction of both the tibial and fibular attachments of the popliteus tendon should be perw125x is per¨ formed. Originally described by Muller formed drilling two tunnels: a first 4.5 mm one drilled from anterior to posterior in the lateral aspect of the tibia and a second one the fibular head. This can be accomplished using a split patellar tendon autograft or a split Achilles tendon allograft, with the proximal end of the graft attached to the lateral femoral condyle and the distal ends fixed separately in tibial and fibular tunnels (Fig. 6). Isolated popliteofibular reconstruction can be accomplished in the above manner with a single tunnel through the proximal fibula instead of two tunnels in the proximal tibia and fibula. Additionally, Veltri and Warren w133x recommended a proximal, valgus tibial osteotomy in patients with chronic posterolateral instability and varus malalignment. Reconstruction of injured posterolateral structures can be performed at a later date if needed. 9. Conclusion Despite the numerous anatomic, biomechanical and clinical studies about PCLyPLC injuries, there is much to be learned. Traditionally, isolated injuries of the PCL were thought to have a benign clinical course. There is recent evidence, however, that such injuries lead to progressive instability and degenerative joint disease. Several techniques for reconstructing both the PCL and the PLC have been described in the literature. Biome-

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Fig. 6. Intraoperative view of a posterolateral reconstruction using the ¨ bypass procedure of Muller. Note the point of entry of the tibial tunnel (as indicated with the arrow) and the free strand of the graft before passing through the fibular head.

chanical studies have evaluated many of these reconstruction techniques with favourable results. Clinical results of PCL and PLC reconstruction, however, remain unsatisfactory. Many patients treated surgically experience residual knee laxity, pain, and functional limitations. Additional basic science and clinical research is needed that will improve current reconstruction techniques and establish a form of treatment that will benefit the patient with isolated and combined PCL injuries.

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