Chapter 23 Rehabilitation of Posterior Cruciate Ligament and Posterolateral Reconstructive Procedures

Frank R. Noyes, MD, Sue D. Barber-Westin, BS, Timothy P. Heckmann, PT, ATC

PROTOCOL FOR PARTIAL OR ACUTE ISOLATED PCL RUPTURES 634

POSTEROLATERAL RECONSTRUCTION REHABILITATION 650

Clinical Concepts

A paucity of information exists in the literature concerning rehabilitation after reconstruction of the posterior cruciate ligament (PCL) and posterolateral structures. The posterolateral structures comprise the fibular collateral ligament and popliteus muscle-tendon-ligament unit, including the popliteofibular ligament and posterolateral capsule.

The rehabilitation protocols described in this chapter consist of a careful incorporation of exercise concepts supported by scientific data and clinical experience.^3,^14,^15,¹⁷ The goal is to progress a patient on a rate that takes into account athletic and occupational goals, condition of the articular surfaces and menisci, return of muscle function and lower limb control, postoperative graft healing, and graft remodeling. Modifications to the postoperative exercise program may be required if noteworthy articular cartilage deterioration is found during surgery.

The protocol for PCL reconstruction was developed for a high-strength two-strand graft (quadriceps tendon–bone, bone–patellar tendon–bone). The protocol for posterolateral reconstruction may be used after the various operative options described in detail in Chapter 22, including anatomic and proximal advancement techniques of the posterolateral structures and nonanatomic femoral-fibular reconstruction.

The supervised rehabilitation programs are supplemented with home exercises performed daily. The therapist must routinely examine the patient in the clinic in order to implement and progress the appropriate protocol. Therapeutic procedures and modalities are used as required for successful rehabilitation. For the majority of patients, a range of 11 to 21 postoperative physical therapy visits is expected to produce a desirable result. A few more visits may be required for advanced training between the 6th and the 12th postoperative month for certain patients who desire to return to strenuous activities.

Critical Points CLINICAL CONCEPTS

• Protocol for posterior cruciate ligament reconstruction for procedures with high-strength two-strand graft (quadriceps tendon–bone, bone–patellar tendon–bone).

• Progress patient on athletic and occupational goals, condition of the articular surfaces and menisci, return muscle function, postoperative healing, remodeling.

• Supervised rehabilitation program supplemented with home exercises performed daily.

• Monitor joint swelling, pain, gait pattern, knee motion, patellar mobility, muscle strength, and flexibility continually after surgery.

• Avoid any exercises or activities that place high posterior shear forces on the tibia such as walking down inclines, squatting, or hamstring flexion curl machines for the first 6 postoperative mo.

• Avoid strenuous activities for 9–12 mo and activities that produce pain, swelling, or a feeling of instability.

• Posterolateral reconstruction: too early resumption of weight-bearing is deleterious to healing graft.

For all patients, joint swelling, pain, gait pattern, knee motion, patellar mobility, muscle strength, and flexibility are continually monitored postoperatively.

Patients are warned to avoid any exercises or activities that place high posterior shear forces on the tibia such as walking down inclines or squatting for the first 6 postoperative months. In addition, patients are cautioned that an early return to strenuous activities postoperatively carries a risk of a repeat injury or the potential of compounding the original injury. These risks cannot always be scientifically predicted, and patients are cautioned to avoid strenuous activities for 9 to 12 postoperative months and to avoid activities that produce pain, swelling, or a feeling of instability. These patients are monitored after surgery with posterior drawer testing and stress radiography if an increase in posterior tibial displacement is detected.

Patients with posterolateral reconstruction are warned specifically at the 4th to 8th postoperative weeks that, with resumption of weight-bearing and weaning of crutches, to avoid a varus or internal tibial rotation position that could place high tensile forces on the posterolateral structures.^13,¹⁶ It is important that the patient demonstrates good lower extremity control with suitable muscle strength to maintain tibiofemoral compensation and avoid a lift-off of the lateral tibiofemoral joint, which may disrupt the posterolateral reconstruction.

PCL Clinical Biomechanics

Kaufman and coworkers ⁸ used a three-dimensional biomechanical model to predict dynamic patellofemoral and tibiofemoral forces generated during isokinetic exercises at 60°/sec and 180°/sec. During isokinetic extension, posterior shear forces were detected at knee flexion angles of 40° and greater. The maximum posterior shear force occurred at 70° to 80° of knee flexion and measured 0.5 ± 0.1 body weight at 60°/sec and 0.6 ± 0.1 body weight at 180°/sec

A posterior shear force occurred throughout the entire flexion exercise at all knee flexion angles, reaching a peak at 75° of knee flexion of 1.7 ± 0.8 body weight (60°/sec) to 1.4 ± 0.5 body weight (180°/sec). The authors concluded that isokinetic exercise exerted moderate posterior shear forces and should be used cautiously after PCL rupture and reconstruction.

Ohkoshi and associates ¹⁹ used a two-dimensional model to calculate shear force exerted on the tibia during standing at various knee flexion angles in 21 healthy subjects. Posterior shear forces were found in the upright position of the trunk and at knee flexion angles of 15° to 90° (Fig. 23-1). At 30° and 60°, the posterior drawer force was significantly increased by anterior flexion of the trunk.

FIGURE 23-1 Calculated shear force (kilograms) per body weight (kilograms) while standing on both legs at various flexion angles of the knee and trunk.

(From Ohkoshi, Y.; Yasuda, K.; Kaneda, K.; et al.: Biomechanical analysis of rehabilitation in the standing position. Am J Sports Med 19:605–611, 1991.)

Castle and colleagues ⁴ measured posterior tibial subluxation during a static double-legged squat in patients with PCL-deficient knees. The results revealed a statistically significant mean increase of 5.9 mm in posterior tibial translation (P < .05) of the injured knee compared with the contralateral knee at high knee flexion angles. At low flexion angles, the magnitude of increase in mean posterior tibial translation was only 2.1 mm. Tibiofemoral shear forces were small compared with tibiofemoral joint compression forces.

Berchuck and coworkers ² calculated large posterior shear forces during gait analysis for the activities of jogging, ascending stairs, and descending stairs (Fig. 23-2) in five normal subjects. Lutz and associates⁹ evaluated tibiofemoral joint shear and compressive shear forces using a two-dimensional biomechanical model and electromyographic (EMG) activity of hamstrings and quadriceps muscle activity during a closed kinetic chain (CKC) leg press exercise, an isometric open kinetic chain (OKC) exercise, and an OKC flexion exercise. Measurements of maximum muscle contractions were obtained at 30°, 60°, and 90° of knee flexion. The OKC isometric flexion exercise produced posterior shear forces at all knee flexion angles (Fig. 23-3), ranging from –939 ± 174 N at 30° of knee flexion to a maximum of –1780 ± 699 N at 90° of knee flexion. The CKC exercises produced significantly less posterior shear forces at 60° and 90° of flexion (–538 N; P < .05). These findings were similar to those reported by Smidt²¹ during isometric knee extension and flexion exercises (Fig. 23-4). Maximum hamstrings EMG activity was detected during the OKC exercise at 90° of flexion (82 ± 15% of maximum contraction). The antagonistic muscle activity was minimal during this exercise at all knee flexion angles. In contrast, co-contraction of the quadriceps and hamstrings was observed during the CKC exercise, which was greatest at 30° and 60° of flexion. The authors concluded that CKC exercise produced significantly less tibiofemoral shear forces compared with OKC exercise (P < .05).

FIGURE 23-2 Calculated tibiofemoral shear forces during activities.

FIGURE 23-3 Average tibiofemoral shear forces observed during the closed kinetic chain leg press, the open kinetic chain extension, and the open kinetic chain flexion exercise.

(From Lutz, G. E.; Palmitier, R. A.; An, K. N.; Chao, E. Y.: Comparison of tibiofemoral joint forces during open-kinetic-chain and closed-kinetic-chain exercises. J Bone Joint Surg Am 75:732–739, 1993.)

FIGURE 23-4 Calculated tibiofemoral shear forces during isometric knee extension and flexion.

Critical Points POSTERIOR CRUCIATE LIGAMENT CLINICAL BIOMECHANICS

• Isokinetic flexion exercise exerts moderate posterior shear forces, use cautiously after PCL reconstruction.

• Posterior shear forces significantly increased during standing by anterior flexion of the trunk.

• Static squat: Significant increase in posterior tibial translation occurs at high knee flexion angles.

• Large posterior shear forces exist during jogging, ascending and descending stairs.

• OKC flexion exercise produces posterior shear forces beyond 30° of knee flexion.

• CKC leg press produces significantly less posterior shear forces than OKC flexion. Co-contraction of quadriceps and hamstrings occurs during CKC, greatest at 30° and 60° of knee flexion.

• Posterior shear forces during CKC squat exercise are relatively low from 0° to 45° of knee flexion. Co-contraction of quadriceps and hamstrings occurs from 0° to 30° of flexion.

• OKC knee extension produces posterior shear forces from 60° to 100° of knee flexion, but these forces are lower than those measured during CKC leg press and squat exercises.

• Leg press induces minimal hamstring muscle activity.

• In situ forces in the PCL significantly increase with knee flexion in response to an isolated hamstrings load, reaching a maximum at 90° of flexion. A simulated co-contraction of the quadriceps and hamstrings reduces the in situ forces in the PCL.

• Isokinetic extension exercise at knee flexion angles less than 70° is safe early postoperatively.

• Isokinetic flexion and deep squats should be avoided early after PCL reconstruction.

• Hamstrings load significantly increases PCL force from 15° to 120° of knee flexion

• The application of tibial torque in either an anterior or a posterior direction when the knee is flexed greater than 60° increases PCL force. Isolated hamstrings activity (with tibial torque) further increases PCL force.

CKC, closed kinetic chain; OKC, open kinetic chain; PCL, posterior cruciate ligament.

Wilk and colleagues ²³ evaluated tibiofemoral shear forces and EMG activity of the quadriceps, hamstrings, and gastrocnemius muscles during OKC extension and CKC leg press and squat exercises. Both CKC exercises produced posterior shear forces. However, during the squat, these forces were relatively low (245–565 N) from 0° to 45° of knee flexion. A rapid increase in posterior shear forces was detected from 45° to 72° of flexion. In addition, co-contraction of the quadriceps and hamstrings occurred from 0° to 30° of flexion. The authors concluded that vertical squats from 0° to 45° of flexion should not be performed in knees in the early stages of PCL reconstruction rehabilitation.

Wilk and colleagues ²³ also found that the knee extension exercise produced posterior shear forces from 60° to 100° of knee flexion; however, these forces were lower than those measured during both CKC exercises. The leg press induced minimal hamstring muscle activity.

Hoher and coworkers ⁷ reported that the in situ forces in the PCL significantly increased with knee flexion in response to an isolated hamstrings load, reaching a maximum at 90° of flexion. These findings were in agreement with other authors^5,²⁴ who also reported increased strain in the PCL with knee flexion. The addition of a 200-N quadriceps load (simulating co-contraction of the quadriceps and hamstrings) reduced the in situ forces in the PCL.

Toutoungi and associates ²² combined noninvasive experimental measurements with geometrical modeling of the lower extremity to calculate ligament forces during isometric, isokinetic, and squat exercises. The data indicated that isokinetic extension at knee flexion angles less than 70° should be safe in the early postoperative period after PCL reconstruction. However, isokinetic flexion and deep squats should be avoided. During isokinetic flexion, only the PCL is loaded and peak forces may reach over 4 times the patient’s body weight at 90° of knee flexion. During squatting, PCL forces may reach 3.5 times body weight at high knee flexion angles. Shallow squats with knee flexion angles kept below 50° may be considered.

Markolf and colleagues ¹⁰ studied the effects of muscle loads on cruciate force levels when the knee was subjected to external forces and moments. Load cells were installed into cadaveric knees to record forces in the ACL and PCL under five loading conditions. These force measurements were repeated with a 100-N load applied to the quadriceps tendon and with a combined 50-N load applied to both the biceps and the semimembranosus-semitendinosus tendons.

With no applied tibial force, application of hamstrings load significantly increased mean PCL force from 15° to 120° of knee flexion (Fig. 23-5; P < .05). With the application of a 100-N posterior tibial force, the addition of hamstrings load significantly increased mean PCL force between 30° and 105° of flexion (Fig. 23-6; P < .05). When a 5-Nm external tibial torque was applied, the addition of hamstrings load significantly increased mean PCL force beyond 75° of knee flexion (P < .05). Under a 5-Nm internal tibial torque, application of hamstrings load also significantly increased mean PCL force between 60° and 100° of flexion (P < .05). The authors concluded that, in general, the hamstrings were more effective in producing changes in cruciate force levels. Application of tibial torque in either an anterior or a posterior direction when the knee was flexed greater than 60° increased PCL force, and isolated hamstrings activity (with tibial torque) further increased PCL force.

FIGURE 23-5 Posterior cruciate ligament (PCL) forces from 0°–120° of knee flexion with no tibial force. Application of a 100-N hamstrings load significantly increased mean PCL force at flexion angles greater than 15°.

(From Markolf, K. L.; O’Neill, G.; Jackson, S. R.; McAllister, D. R.: Effects of applied quadriceps and hamstrings muscle loads on forces in the anterior and posterior cruciate ligaments. Am J Sports Med 32:1144–1149, 2004.)

FIGURE 23-6 PCL forces from 0°–120° of knee flexion under a constant 100-N posterior tibial force. Application of a 100-N hamstrings load significantly increased mean PCL force at flexion angles between 30° and 105°.

Protocol for Partial or Acute Isolated PCL Ruptures

This program does not apply to PCL avulsions in which surgery may be indicated and partial tears with 5 mm or less of increased posterior tibial translation. The goal with completePCL disruptions (8–10 mm of increased posterior tibial translation at 90° flexion) is to allow PCL healing and possibly reduce some of the posterior tibial translation. Importantly, this includes maintaining normal tibiofemoral contact at full knee extension or with knee flexion. An anterior drawer produced by the therapist during motion will allow for healing of PCL fibers with the least amount of residual abnormal PCL elongation and posterior tibial translation. Although clinical data are not available, the empirical favorable experience of the authors warrants the program described below.

The rules to treat partial or acute isolated PCL tears are

1 Protect for 6 weeks in full knee extension with a brace and posterior calf pad (Fig. 23-7) or bivalved cylinder cast to maintain tibiofemoral reduction. Use quadriceps isometrics, electrical muscle stimulation (EMS), leg raises, and 25% weight-bearing.

2 Obtain a lateral radiograph to verify that no posterior tibial subluxation exists, which can occur in up to 50% of knees.

3 At 2 weeks, the therapist initiates 0° to 90° of motion, maintaining anterior tibial translation load during knee motion exercises. The patient must sleep in the brace and is not allowed unsupervised knee motion. Only passive flexion is permitted.

4 At 4 weeks, the patient is allowed to perform active quadriceps extension out of the brace, use 50% weight-bearing with crutch support, and continue brace protection.

5 At 5 to 6 weeks, the patient is weaned from the brace and crutch support, active full knee flexion is allowed, and the rehabilitation protocol described later beginning at this time period is followed.

FIGURE 23-7 Knee extension brace with posterior calf pad to maintain tibiofemoral reduction.

PCL Reconstruction Postoperative Protocol

Immediate Postoperative Management

Patients present to physical therapy the 1st day after surgery on bilateral axillary crutches in a postoperative dressing with a long-leg brace locked in full extension (Table 23-1). The postoperative bandage and dressing are changed to allow the application of thigh-high compression stockings and a compression bandage. Early control of postoperative effusion is essential for pain management and early quadriceps reeducation. In addition to compression, cryotherapy is important in this time period.

TABLE 23-1 Rehabilitation Protocol after Posterior Cruciate Ligament Reconstruction