Surgical treatment of ACL/PCL/ lateral-side knee injuries

Acute injuries 

Repair, augmentation, or reconstruction of the damaged ligaments is preferred for most patients, provided that they have satisfactory vascular supply, soft tissues, and rehabilitation potential. Surgical exploration and treatment of all involved structures provides the most reliable results, and early surgery is always advised when the cruciate ligaments are torn in combination with the FCL. The posterolateral structures are important secondary restraints to anterior and posterior translation.6, 7 Posterolateral repair or reconstruction is at risk for attenuation if the ACL and/or PCL are not reconstructed. In addition, cadaver studies have shown that posterolateral deficiency results in increased ACL and PCL graft forces.8, 9 Posterolateral repair or reconstruction is recommended at the time of ACL or PCL reconstruction to decrease the chance of ACL or PCL graft failure.10

Anatomic repair of the lateral and posterolateral structures is more difficult if the surgery is delayed because of tissue retraction and scarring. Proceed with arthroscopically assisted cruciate-ligament reconstructions and lateral-side anatomic repair within 2 weeks of the traumatic event. Repair and augment if necessary the FCL, popliteofibular ligament, posterolateral corner, and associated tendinous injuries (biceps, popliteus, iliotibial band).

Position the injured leg very carefully during preparation for surgery because the neurovascular structures are vulnerable. Plan to use the arthroscope even when the procedure is performed with an open technique. The arthroscope serves as an excellent illumination, magnification, and irrigation tool. Use the arthroscope to assist with diagnosis, meniscus repair, and preparation of bone tunnels for cruciate-ligament reconstruction. If the joint capsule is disrupted, ensure adequate fluid outflow and monitor extravasation to prevent a compartment syndrome.

Employ a straight anterolateral paramedian skin incision or a posterolateral incision combined with small anteromedial incisions for the cruciate-ligament reconstructions. Develop full-thickness skin flaps and handle the soft tissues carefully to minimize wound-healing problems. Isolate or at least be aware of the peroneal nerve location posterior to the biceps tendon. Expose the lateral and posterolateral knee by splitting the iliotibial band in line with its fibers in addition to developing the interval between the posterior iliotibial band and the biceps femoris. A more extensile exposure is accomplished by detaching the iliotibial band insertion with a block of bone from Gerdy’s tubercle. Proximal retraction of the ITB facilitates identification and repair of the lateral and posterolateral structures. Repair the ITB insertion anatomically with screw fixation at the conclusion of the procedure. Systematically identify each injured ligament and tendon. Place a locking whipstitch (Number 2 or Number 5 nonabsorbable suture) in each structure for later repair or augmentation.

Perform the arthroscopic meniscal treatment, cruciate-ligament reconstruction tunnel drilling, graft passage, and femoral fixation before definitive repair of the lateral and posterolateral structures (Table 1). Reconstruct both cruciate ligaments as necessary. Cruciate-ligament repair with reattachment to the femur or tibia is occasionally possible if periosteal or bony avulsion is encountered. Typically, intrasubstance ligament damage with attenuation occurs before actual rupture; therefore, anatomic reattachment may result in unacceptable ligament tension and a “nonfunctional” ligament. Expose a PCL insertion bone avulsion with a simplified posterior approach that retracts the medial gastrocnemius laterally.11 Reattach the ligament by using a screw and spiked ligament washer and nonabsorbable locking whipstitch sutures pulled through drill holes or tied around a screw post. Reconstruct a midsubstance PCL disruption with a patellar tendon or Achilles tendon allograft. Reconstruct the ACL with a patellar tendon or semitendinosus/gracilis autograft or patellar tendon allograft according to the surgeon’s preference (Fig 3). Use ACL and PCL allografts from the same donor if possible. Fix both the ACL and PCL grafts on the femoral side, but wait to tension and fix the grafts on the tibial side until after the lateral and posterolateral repairs are complete. ACL graft tension may cause increased tibial external rotation if the posterolateral structures are incompetent.12

TABLE 1. Surgical Sequence

	1.Expose and isolate the injured lateral and posterolateral structures 2.Perform diagnostic arthroscopy, articular surface, and meniscus treatment as necessary 3.Drill PCL tibial tunnel 4.Drill ACL tibial tunnel (maintain ≥ 1 cm of bone between the tunnels) 5.Drill ACL femoral tunnel 6.Drill PCL femoral tunnel 7.Fix PCL and ACL grafts on femoral sides only 8.Repair, augment, or reconstruct fibular collateral ligament and popliteofibular ligament. 9.Repair popliteus tendon, biceps tendon, iliotibial band, and lateral gastrocnemius tendon 10.Repair the coronary ligament, arcuate ligament, and mid-third lateral capsular ligament 11.Repair capsule from posterior to anterior 12.Tension and fix PCL graft at 80° flexion 13.Tension and fix ACL graft in full extension 14.Intra-operative radiograph to check the position of the screws and to verify tibiofemoral reduction

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Fig 3. Arthroscopic photograph of a patellar tendon allograft ACL reconstruction and Achilles tendon allograft PCL reconstruction.

Reattach a proximal avulsion of the FCL and the popliteus tendon into a 4- to 6-mm bone trough at their anatomic attachment sites in an attempt to restore isometry and proper tension. Fix the ligament and tendon with a locking whipstitch, nonabsorbable suture passed through femoral drill holes and tied over a medial bone bridge, or with a screw and ligament washer combined with sutures tied around the screw. Reattach a distal avulsion of the FCL, popliteofibular ligament, and the biceps tendon to the fibular head through drill holes or with suture anchors. Repair the coronary ligament, arcuate ligament, and mid-third lateral capsular ligament anatomically. Repair the menisci, popliteomeniscal fascicles, and osteochondral fractures whenever possible. Fig 4 represents postoperative anteroposterior and lateral radiographs after allograft reconstruction of the ACL and PCL, along with repair of the FCL and popliteus tendon to the femur. When the fibular collateral and/or popliteofibular ligaments are inadequate for an isolated repair, use a free semitendinosus autograft for augmentation or reconstruction.13 Pass the free semitendinosus graft through a 6-mm fibular head tunnel. Tension the graft and fix both ends into a 25-mm socket at the lateral epicondyle with an interference screw. Obtain additional fixation by tying the lead sutures over a button on the medial femur.

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Fig 4. Postoperative anteroposterior (A) and lateral (B) radiographs after acute FCL and popliteus tendon repair combined with ACL and PCL reconstructions.

Chronic injuries 

Before any ligament reconstruction surgery, lower extremity alignment must be analyzed and corrected as necessary. Observe the patient’s gait to identify the dynamic component of the deformity, such as a varus (lateral) thrust or hyperextension that may not be apparent on standing radiographs. Failure to rectify malalignment and gait abnormalities will result in compromise of any soft-tissue reconstruction procedure.

Correct hyperextension before surgery with bracing, heel lifts, muscle strengthening, and gait retraining. Correct the malalignment in the coronal plane with a valgus-producing (antivarus) proximal tibial osteotomy. A medial opening wedge technique is preferred to avoid resection of the proximal tibiofibular joint or a fibular osteotomy (Fig 5). Measure the anatomic axis, mechanical axis, and the weight-bearing line on full-length standing radiographs. Static analysis of the full-length roentgenogram (51 × 14 inches) remains the standard process for determining the magnitude of correction. The mechanical axis of the limb is the angle formed between a line drawn from the hip center to the knee center (femoral mechanical axis) and a line drawn from the knee center to the ankle center (tibial mechanical axis). The normal mechanical axis is approximately 1.2° of varus.14 The weight-bearing line method is simple and reproducible technique for determining the desired correction angle.15 Divide the lateral tibial plateau from 0 to 100% from the medial to the lateral margins. Draw lines from the center of the femoral head and the center of the tibiotalar joint to the 62% coordinate on the tibial plateau. The angle formed by these 2 lines equals the calculated angle of correction. The use of standing radiographs can overestimate the magnitude of correction due to ligament attenuation. Each millimeter of lateral tibiofemoral joint separation causes approximately 1° of varus angular deformity. Compare the amount of lateral joint-space opening (in millimeters) with the contralateral knee and subtract the difference from the calculated angle (1° per millimeter) to obtain the final angle of correction. This adjustment is important to avoid overcorrection. Perform an opening wedge, medial, proximal tibial osteotomy to produce the desired valgus correction in the coronal plane and a neutral tibial slope in the sagittal plane. Increased posterior tibial slope places excessive strain on the ACL graft and increased anterior tibial slope places excessive strain on the PCL graft. The sagittal plane alignment can be manipulated by using an opening wedge plate with a trapezoidal block instead of a rectangular block.

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Fig 5. Postoperative anteroposterior radiograph after a first stage valgus-producing medial opening wedge proximal tibial osteotomy in a patient with a previous failed isolated FCL repair (fibular head screw).

After approximately 6 months, when the osteotomy has healed, perform FCL, popliteofibular ligament, and popliteus tendon reconstructions as necessary. The important contribution of the popliteofibular ligament to knee stability has been well documented. Cadaver testing has shown that the popliteofibular ligament is dominant when the knee is flexed due to slackening of the FCL.16 Reconstruction of the popliteofibular ligament is important to withstand tibial external rotation forces at higher knee flexion angles. Occasionally, the FCL and popliteus tendon can be tensioned by advancement if these structures are intact but retracted from their femoral attachments. The isometric point is nearly maintained by recessing the ligament and tendon into a 4- to 6-mm bone trough that is slightly proximal and anterior to the lateral epicondyle. Fix the FCL and the popliteus tendon by passing the nonabsorbable locking whipstitch sutures through femoral drill holes and then tying these sutures over button on the medial femur.

When reconstructions are required, graft choices include Achilles tendon allograft and semitendinosus or patellar tendon autograft/allograft. The Achilles tendon provides excellent strength and a bone block for fixation at the femoral attachment. This tendon is wide enough to split so that 3 arms can be used to reconstruct the FCL, popliteofibular ligament, and the popliteus tendon if necessary. Fix the bone block with an interference screw in an 8-mm tunnel at the lateral epicondyle (Fig 6). Pass the free end of the graft through a 7-mm fibular head tunnel oriented from distal lateral to proximal medial to recreate the insertion sites of the FCL and popliteofibular ligament (Fig 7). Route the oblique arm of the figure-eight graft deep to the vertical arm to insert anterior and distal to the femoral bone tunnel. The vertical arm reconstructs the FCL and the oblique arm reconstructs the popliteofibular ligament. The Achilles tendon graft can be split if a third arm is necessary to reconstruct the popliteus tendon (Fig 7). Pass the graft through an 8-mm tibial tunnel from posterior to anterior. Fix the graft to the anterolateral tibia with a screw and ligament washer.

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Fig 6. Intraoperative photograph of an Achilles tendon allograft used for FCL and popliteofibular ligament reconstruction combined with ACL and PCL reconstructions.

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Fig 7. Drawing of an Achilles tendon allograft technique for reconstruction of the FCL and popliteofibular ligament. Additional graft arm is passed through a tibial tunnel (dashed lines) to reconstruct the popliteus tendon if necessary.

Rehabilitation 

Apply a soft compressive dressing with plaster splints after surgery that maintains the knee in slight flexion. After limb swelling improves, change to a custom polypropylene knee—ankle—foot orthosis or a rehabilitation brace that includes the foot. The hinge provides protection against varus and external rotation stresses, along with an extension lock and a 90° flexion stop. The brace is locked in extension at all times except when performing range-of-motion exercises. General rehabilitation guidelines during the first 4 weeks include prone passive flexion from 0° to 90°, touch weight bearing with brace locked in extension, patellar mobilization, isometrics and straight-leg lifts, and electrical muscle stimulation as necessary. After 4 weeks, begin both passive- and active-assisted gradual full flexion, partial weight bearing with the brace locked in extension, and low resistance closed-chain strengthening exercises, including mini squats and leg press. After 8 weeks, begin full active range of motion, full weight bearing with the brace locked in extension, progressive resistance closed-chain strengthening exercises, low-resistance bicycling, and swimming. After 3 months, begin full weight bearing in an unloader brace with a slight valgus moment, low-resistance bicycling, swimming, and hamstring strengthening. Patients continue their strengthening and proprioceptive training exercises and wear the brace for the ensuing year.