Indications

Although most authors strongly support aggressive surgical treatment for patients with acute knee dislocations, there are indications to consider nonoperative or nonreconstructive treatment. Patients who should be considered for less aggressive treatment include poor surgical candidates and patients with a severely damaged closed soft tissue envelope.

Techniques

Indications and Treatment Algorithm

The vast majority of patients who have sustained knee dislocations should undergo surgical treatment. An algorithm is helpful in determining the surgical treatment for patients with knee dislocations (Fig. 31.3).

Contemporary treatment can be divided into two major categories: treatments that depend on immobilization, and treatments that enable early mobilization of the knee.38

Methods that enable early mobilization of the knee involve various repairs and reconstructions of ligaments. The definition of early mobilization varies from 1 day to approximately 4 weeks following surgery. The major benefit of early mobilization is a reduction of intra-articular scar tissue with a subsequent decrease in pain and improved motion. The risk of early motion is increased wound healing problems and ligamentous laxity. But we believe that most patients should be treated with a method that enables early mobilization of the knee joint so as to improve final range of motion and to limit pain and intra-articular scar tissue formation.

Patients who sustain a multi-ligament knee injury should be evaluated in the emergency department with a careful neurologic and vascular exam, with special attention paid to assessing the vascular supply below the knee and the neurologic function of the peroneal and tibial nerves. The patient′s skin should be carefully scrutinized to rule out an open dislocation, and a careful exam of the ipsilateral lower extremity should be conducted to detect any associated fractures. If the knee is still dislocated, a reduction should be performed. If the knee is irreducible and the patient has a normal vascular exam, the patient should be taken to the operating room for an open reduction. A knee immobilizer should be applied and formal repair or reconstruction delayed for approximately 2 to 4 weeks to enable soft tissue recovery. If the vascular exam is abnormal, an emergent consultation with a vascular surgeon and open exploration of the popliteal artery should be pursued. An option is to obtain an ankle-brachial index (ABI) to confirm vascular injury. An ABI less than 0.9 is indicative of a significant vascular injury. Ligament reconstruction is delayed for at least 2 to 4 weeks to enable soft tissue and vascular recovery prior to embarking on extensive reconstructive procedures.

Most patients who are active and cooperative should undergo repair or reconstruction of the torn ligaments in their knee. We recommend initiating repair or reconstruction within 2 to 4 weeks to enable early mobilization of the knee. The ideal timing for ligament repair or reconstruction is not clearly delineated in the literature. Controversy exists regarding repair/reconstruction of all ligaments at one surgery compared with delayed reconstruction of the ACL after early rehabilitation of the PCL, posterolateral corner (PLC), and posteromedial corner (PMC). Authors report success with both methods, and each has its advantages. One of the authors of this chapter reconstructs all ligaments simultaneously, whereas the other does everything except the ACL initially, followed 6 weeks later by ACL reconstruction.

Anatomy

Conceptually, the anatomy of the knee is divided into four structures: ACL, PCL, PLC, and PMC.

Important palpable landmarks about the knee include the medial and lateral femoral epicondyles (collateral ligament origins), the tibial (patellar tendon insertion) and Gerdy′s (iliotibial band insertion) tubercles, the posteromedial border of the proximal tibia, and the fibular head. The frequent need to explore the PMC or PLC in the surgical management of the dislocated knee makes knowledge of these landmarks critical. Any approach to the ligamentous corners is based on the femoral epicondyle, posterior tibial border medially, and fibula laterally. With respect to the posterolateral approach, the peroneal nerve must be explored, with neurolysis a critical first step prior to any ligamentous or tendon reconstructive work on the lateral side of the knee. Important landmarks for the posteromedial approach include the medial collateral ligament (MCL) inserting broadly just underneath the pes tendons and anterior to the posterior border of the medial tibia.

The vascular supply about the knee is a complex anastomosis of two separate systems: the intrinsic and extrinsic networks. The intrinsic vascular supply is an anastomotic ring made up of the articular, muscular branches and five geniculates. The geniculates are the superomedial and lateral geniculates, the middle geniculate, and the inferior medial and lateral geniculates. The anastomotic network provides for a rich blood supply to the skin overlying the knee and patella and enables vascularity even with subcutaneous dissection. When parallel incisions are utilized (such as parallel medial and lateral incisions), the skin flaps are dependent on the width of the superior and inferior vascular pedicles of the extrinsic system. Planning of such incisions to avoid skin bridge necrosis should have an appropriate width of at least 5 to 7 cm between incisions. With proper planning, skin loss is rare, but it can occur and is covered most frequently with a rotationplasty of the medial gastrocnemius muscle. Although the intrinsic/extrinsic vascular system provides adequate vascularity for superficial knee dissections, the anastomotic ring provides inadequate collateral flow to the lower leg with popliteal flow disruption.

The knee joint has a complex anatomic arrangement of muscular and ligamentous attachments. A layer system has been described that is useful to understand the complex and varied anatomy of the PLC and PMC of the knee. The layer system is divided into three sections labeled with the Roman numerals I, II, and III (Fig. 31.4). Layer I is the most superficial fascial layer, with the deeper layers sequentially numbered II and III. Layer I is described as the arciform or Marshall′s layer anteriorly, the sartorius fascia medially, and the iliotibial band and biceps femoris fascia laterally. Layer II includes the patellar tendon, superficial MCL, and the fibular collateral ligament. Layer III is defined as all joint capsular structures, including the functional capsular thickenings of the posterior oblique and arcuate ligaments, the deep MCL, and the middle one-third lateral joint capsule (responsible for the Segond fracture). Simplistically, but accurately, layer III includes all joint capsular structures but has multiple anatomic variations in thickness, creating distinct ligaments about the PLC and PMC. Anteriorly, the joint capsule, or layer III, is thin and adherent to the posterior aspect of the patellar tendon. Posterolaterally, the capsule thickening is named the arcuate ligament (posterior one-third capsule, laterally) and is thickened posteromedially as the posterior oblique ligament (posterior one-third capsule medially). The PLC and ligaments have great variability and confusing nomenclature when reviewing the anatomic literature.42 With any posterolateral reconstruction, both the popliteofibular and fibular collateral ligament should be reconstructed.

Posteromedial Approach to the Knee

The posteromedial approach is very useful in patients with complex knee injuries. Variations of this approach have been utilized by Burks43 and by Berg16 to approach the tibial attachment of the PCL. Open treatment of knee dislocations for reconstruction of the PCL and the PMC can be accessed via this approach,44 as well as using it for simultaneous repair of vascular and ligament injuries.16,26,44

The patient is positioned supine, and the incision is placed along a line from the medial epicondyle to the insertion of the tibial collateral ligament along the posteromedial border of the tibia. With the patient′s knee flexed and the hip externally rotated in the figure-of-four position, the posteromedial approach can be performed with the patient in a supine position, and it is our preferred approach. The saphenous vein and nerve may be encountered and should be protected. The tendons of the pes anserinus can simply be retracted distally. The semimembranosus (Fig. 31.5) is variable in its insertion and in our experience usually requires release at its insertion, but it is tagged for later repair. The medial head of the gastrocnemius muscle is then identified. The remainder of the surgical approach remains anterior to the gastrocnemius, hugging the proximal tibial plateau and medial femoral condyle. In this approach to the PCL, all retractors must remain anterior to the medial gastrocnemius and popliteus to avoid injury to the popliteal vessels. The medial head is routinely not released (Fig. 31.6). Keeping the knee flexed to 70 degrees relaxes the posterior neurovascular bundle, creating added safety with an approach anterior to the gastrocnemius. In the presence of a knee dislocation and evidence of MCL insufficiency, capsular structures may be completely disrupted, enabling exposure of the knee joint itself.

Posterolateral Approach to the Knee

This approach is useful for reconstruction of posterolateral ligamentous injuries, mobilization of the lateral gastrocnemius muscle for soft tissue coverage procedures, and exploration and repair of the common peroneal nerve. It is frequently useful in knee dislocations and is critical in reconstruction of the PLC. The peroneal nerve is always isolated prior to deep joint exposure to prevent inadvertent injury to the nerve. In dislocations with complete tears of both cruciates, the ligaments are frequently disrupted circumferentially.

The patient is placed in the supine position with a tourniquet on the thigh and a small bump under the ipsilateral buttock. The knee joint is best exposed with the knee flexed to 90 degrees, enabling relaxation and protection of the peroneal nerve. The skin incision is placed in line with the fibular head and carried in a straight line proximally, then curving onto the lateral thigh. With proximal extension, the incision should curve between the iliotibial band (ITB) and biceps femoris tendon. The incision is carried down to the deep fascia, which is then opened carefully with scissors. At this point the peroneal nerve must be identified and can usually be palpated subfascially as it courses from the biceps femoris through its perineural fat to the fibular neck. The posterolateral approach should always include exposure of the peroneal nerve prior to deep dissection and ligamentous reconstruction (Fig. 31.7). The peroneal nerve is best identified where it wraps around the fibular neck. Once identified, the nerve is protected with a small vessel loop. Never attach a surgical clamp to the vessel loop as the weight can cause peroneal nerve injury.

Blunt dissection is used to define the plane anterior to the lateral gastrocnemius head (Fig. 31.8). In the exposure of combined ligament injuries of the posterolateral knee, the dissection planes are usually already formed secondary to the translation that occurred with the knee injury. The surgeon should never dissect posterior to the gastrocnemius because it places the popliteal neurovascular structures at risk. If the LCLs are intact, the PCL cannot be identified from this approach. If the ACL, PCL, and LCL are completely torn, the tibial insertion of the PCL (i.e., inlay) can be exposed and performed from this lateral approach. However, we strongly recommend against using the posterolateral approach for the tibial inlay technique of PCL reconstruction, as the posteromedial approach is both easier and safer.

Posterior Cruciate Ligament Reconstruction

Much like ACL reconstruction in the 1980s, PCL reconstruction techniques have evolved over the past 10 to 15 years so that there are now three distinct approaches. The transtibial reconstruction fixes the PCL graft proximally in a femoral tunnel and distally in a tunnel through the proximal tibia. The tibial inlay technique utilizes a similar femoral tunnel for proximal fixation, but distal fixation is obtained by securing a bone plug into a trough positioned at the anatomic insertion of the PCL. The tibial inlay approach places the bone tendon junction of the distal graft at or near the joint line. Finally, the two-tailed femoral technique may be used in combination with a tibial inlay approach in a double-bundle reconstruction.

Transtibial PCL reconstructions have often resulted in residual grade I or II posterior laxity. It has been suggested that two major factors may explain late loosening and low-grade laxity following transtibial PCL reconstruction. The first factor is the acute angle the graft must make to round the posterior lip of the tibia when exiting the transtibial tunnel. This has been described as the “killer turn,” which may lead to abrasion and subsequent laxity and failure (Fig. 31.9).16 This factor is supported by biomechanical studies that found that the inlay technique had zero failures compared with 32% in the transtibial technique using a cadaver model with a mechanical testing system (MTS) machine (MTS Systems, Minneapolis, MN) ranging the knee for 2,000 cycles. There were also significant differences in graft thinning and elongation between the two techniques. The inlay grafts developed 13% thinning and 5.9 mm of graft elongation over 2,000 cycles, compared with 41% thinning and 9.8 mm of graft elongation with the transtibial technique.45

The second factor is that, although the PCL has at least two distinct bundles functionally, which tighten at different degrees of knee flexion,46–49 the transtibial endoscopic technique reproduces only the anterolateral bundle. Some contemporary surgical techniques attempt to address these shortcomings of the transtibial method. The tibial inlay technique addresses the potential problems associated with the killer turn by placing a bone block in a trough on the posterior tibia at the site of insertion of the PCL.16,50–52 It is also possible to eliminate the killer turn by placing the transtibial tunnel exit more distally on the tibia, as will be described below. The two femoral tunnel technique enables reconstruction of both the anterolateral and posteromedial bundles of the PCL.53,54

Tibial inlay techniques at first glance may appear cumbersome but have become more simplified in recent years. Miller and colleagues55 performed an anatomic study showing that the popliteal artery remains an average of 21 mm posterior to the inlay site when the medial head of the gastrocnemius is left intact. An approach to PCL reconstruction that further simplifies the tibial inlay technique maintains the patient in a supine position throughout the procedure and preserves the origin of the medial head of the gastrocnemius.

Double-Bundle Inlay Posterior Cruciate Ligament Reconstruction

Video 31.1 Double-Bundle Inlay PCL Reconstruction

Video 31.2 Arthroscopic Double-Bundle PCL

The anatomic PCL reconstruction is a combination of the tibial inlay16,50–52 and two femoral tunnel53,54 techniques. The patient should be placed in a supine position to enable arthroscopy using a bump under the knee and allowing the leg to hang off the table. An Achilles tendon allograft is divided into a larger anterolateral and a smaller posteromedial bundle. The bone block is trimmed, and permanent No. 2 suture is placed into each bundle using Krackow stitches to assist passage into the appropriate femoral tunnel. The notch is debrided arthroscopically, and any meniscus pathology is addressed simultaneously. When that is complete, a guidewire is drilled 8 to 10 mm from the articular surface within the footprint of the PCL at the top of the intercondylar notch. A second guidewire is placed inferior to the first guidewire, making certain to space them so that there will be approximately a 4-mm bone bridge between the two tunnels (Fig. 31.10). The tunnel size is selected based on the size of the Achilles tendon allografts, with a 9-mm anterolateral tunnel and a 7-mm posteromedial tunnel being the most common sizes (Fig. 31.11). The arthroscope is then removed from the knee and a posterolateral or posteromedial approach to the knee is performed, depending on associated ligament pathology.

A trough is created in the bone at the site of insertion of the PCL into the posterior tibia utilizing a combination of osteotomes, curets, and occasionally a rongeur. The 0.5-inch curved osteotome is the ideal size for this task. A key tip is that a blunt Hohmann or similar retractor must be placed anterior to the gastrocnemius muscle, retracting the muscles and vascular structures posteriorly. Another important point is to keep the patient′s knee flexed any time the surgeon is working in the back of the knee. Fixation is obtained with a single 4.5-mm cannulated screw and washer placed utilizing a lag technique by drilling a 4.5-mm hole through the bone block. It is critical not to make the bone block too thin (Fig. 31.11), or the allograft may crack when tightened. If this occurs, it can be salvaged with staples. The two bundles are then advanced into the notch and into their respective femoral tunnels. The anterolateral bundle is tensioned at ~ 80 degrees of flexion, with the posteromedial bundle tensioned at ~ 15 degrees. Both bundles are secured with absorbable interference screws that are either the same size or 1 mm larger than the size of the tunnel, depending on bone quality. If all four ligament groups in the knee are torn, fluoroscopy may be necessary to confirm that the knee is reduced and that the graft is not overtightened. The results utilizing this technique have been very good, with little if any loosening over time and only a single failure in our first 30 cases. Data with the KT-2000 knee arthrometer demonstrated that the reconstructed PCL was at least as tight as the uninjured side. Lysholm knee scores and clinical laxity exams were also quite encouraging.56

Arthroscopic Transtibial Posterior Cruciate Ligament Reconstruction Surgical Technique

Our preferred graft source for PCL reconstruction is allograft tissue. The anterolateral bundle of the PCL is reconstructed with Achilles tendon allograft and the posteromedial bundle of the PCL is reconstructed with tibialis anterior allograft tissue.

The patient is placed in the supine position on the operating table, and the surgical and nonsurgical knees are examined under general or regional anesthesia. A tourniquet is applied to the operative extremity and the surgical leg prepped and draped in a sterile fashion. Allograft tissue is prepared prior to beginning the surgical procedure. Standard arthroscopic knee portals are used. The joint is thoroughly evaluated arthroscopically and the PCL evaluated using the three-zone arthroscopic technique. The PCL tear is identified and the residual stump of the PCL is debrided with hand tools and the synovial shaver. The PCL insertion sites are left intact to serve as anatomic landmarks. An extracapsular extra-articular posteromedial safety incision approximately 1.5 to 2.0 cm long is created. The crural fascia is incised longitudinally, taking precautions to protect the neurovascular structures. The interval is developed between the medial head of the gastrocnemius muscle and the posterior capsule of the knee joint. The surgeon′s gloved finger is positioned so that the neurovascular structures are posterior to the finger and the posterior aspect of the joint capsule is anterior to the surgeon′s finger. This technique enables the surgeon to monitor surgical instruments, guidewires, and reamers as they are positioned in the posterior aspect of the knee. The posteromedial safety incision facilitates the flow of the surgical procedure, protects the neurovascular structures, and confirms the accuracy of the PCL tibial tunnel position in the medial-lateral and proximal-distal directions. This is the same anatomic surgical interval that is utilized in the tibial inlay posterior approach.

The curved over-the-top PCL instruments (Biomet Sports Medicine, Warsaw, IN) are used to elevate the posterior knee joint capsule away from the tibial ridge on the posterior aspect of the tibia. This capsular elevation enhances correct drill guide and tibial tunnel placement.

The arm of the PCL-ACL Drill Guide (Biomet Sports Medicine) is inserted into the knee through the inferior medial patellar portal and positioned in the PCL fossa on the posterior tibia. The bullet portion of the drill guide contacts the anterior medial aspect of the proximal tibia approximately 1 cm below the tibial tubercle, at a point midway between the tibial crest anteriorly and the posterior medial border of the tibia. This drill guide positioning creates a tibial tunnel that is relatively vertically oriented. This positioning creates a trough on the back of the tibia and an angle of graft orientation such that the graft will turn two very smooth 45-degree angles on the posterior aspect of the tibia, and positions the graft tissue to approximate the tibial anatomic insertion site of the PCL.

The tip of the guide in the posterior aspect of the tibia is confirmed with the surgeon′s finger through the extracapsular posteromedial safety incision. If the surgeon prefers, intraoperative anteroposterior (AP) and lateral X-rays may also be used, as well as arthroscopic visualization to confirm drill guide and guide pin placement; however, the posteromedial safety incision alone provides safety and accuracy. A blunt spade-tipped guidewire is drilled from anterior to posterior. We consider the finger in the posteromedial safety incision the most important step for accuracy and safety.

The appropriately sized standard cannulated reamer is used to create the tibial tunnel. The closed curved PCL curette may be positioned to cup the tip of the guidewire. The arthroscope, when positioned in the posteromedial portal, may visualize the guidewire being captured by the curet, and may help in protecting the neurovascular structures. This, in addition to the surgeon′s finger in the posteromedial safety incision, helps to protect the neurovascular structures. The surgeon′s finger in the posteromedial safety incision is monitoring the position of the guidewire. The standard cannulated drill is advanced to the posterior cortex of the tibia. The drill chuck is then disengaged from the drill, and completion of the tibial tunnel reaming is performed by hand. This gives an additional margin of safety for completion of the tibial tunnel. The tunnel edges are chamfered and rasped with the PCL/ACL system rasp.

The PCL single-bundle or double-bundle femoral tunnels are made from inside out using the double-bundle aimers (Biomet Sports Medicine). Inserting the appropriately sized double-bundle aimer through a low anterior lateral patellar arthroscopic portal creates the PCL anterior lateral bundle femoral tunnel. The double-bundle aimer is positioned directly on the footprint of the femoral anterior lateral bundle PCL insertion site. The appropriately sized guidewire is drilled through the aimer, through the bone, and out a small skin incision. Care is taken to ensure that there is no compromise of the articular surface. The double-bundle aimer is removed and an acorn reamer is used to endoscopically drill from inside out the anterior lateral bundle PCL femoral tunnel. The tunnel edges are chamfered and rasped. The reaming debris is evacuated with a synovial shaver to minimize fat pad inflammatory response. The same process is repeated for the posterior medial bundle of the PCL. Care must be taken to ensure that there will be an adequate bone bridge (approximately 5 mm) between the two femoral tunnels prior to drilling. This is accomplished using the calibrated probe, and direct arthroscopic visualization.

One of the chapter authors prefers a surgical technique of PCL femoral tunnel creation from inside to outside, for two reasons. First, there is a greater distance and margin of safety between the PCL femoral tunnels and the medial femoral condyle articular surface using the inside to outside method. Second, a more accurate placement of the PCL femoral tunnels is possible because the double-bundle aimer or endoscopic reamer can be placed on the anatomic footprint of the anterior lateral or posterior medial PCL insertion site under direct visualization.

A Magellan suture-passing device (Biomet Sports Medicine) is introduced through the tibial tunnel and into the knee joint and is retrieved through the femoral tunnel with an arthroscopic grasping tool. The traction sutures of the graft material are attached to the loop of the Magellan suture-passing device, and the PCL graft material is pulled into position.

Fixation of the PCL graft is accomplished with primary and backup fixation on both the femoral and tibial sides. Femoral fixation is accomplished with cortical suspensory backup fixation using polyethylene ligament fixation buttons, and aperture opening fixation is achieved using the Bio-Core bioabsorbable interference screws (Biomet Sports Medicine). The mechanical graft-tensioning boot (Biomet Sports Medicine) is applied to the traction sutures of the graft material on its distal end and tensioned to restore the anatomic tibial step-off. The knee is cycled through several sets of full flexion-extension cycles for graft pre-tensioning and settling. The PCL reconstruction graft is tensioned in physiological knee flexion ranges. Tibial-sided graft fixation is achieved with primary aperture opening fixation using the Bio-Core bioabsorbable interference screw, and backup fixation is done with a ligament fixation button, screw and post, or screw and spiked ligament washer assembly.57,58

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