INTRODUCTION

Operative procedures to stabilize knees that have suffered ligamentous injuries have recently undergone dramatic changes. Knees that have sustained multiple ligament tears are often initially treated non-operatively to allow the collateral ligaments to heal. The torn cruciate ligaments are replaced at a later time using arthroscopic techniques.

Concepts regarding post-operative rehabilitation following reconstructive knee surgery have also changed. Instead of immobilization, early motion is encouraged after surgery. An extension of this approach is to use immediate and continuous controlled motion of the knee following anterior cruciate ligament (ACL) replacement surgery. Donald Shelbourne developed the concept of accelerated postoperative rehabilitation. (9,10) This article will describe the postoperative rehabilitation proto-col that is used by the senior author (BZ) at the Massachusetts General Hospital that balances early return to sports participa-tion with adequate time for graft healing.

METHODS

We use the accelerated rehabilitation protocol when we replace a torn anterior cruciate ligament with a mid-third patellar tendon graft (bone-tendon-bone) using the endoscopic method. Bioabsorbable interference screws are used in the distal femur and proximal tibia, providing graft fixation comparable to metal screws. (18,19) This technique provides immediate stable fixation and allows the knee to be safely moved using the continuous passive motion (CPM) machine after surgery.

We believe the autologous mid-third patellar tendon graft is the best graft for ACL replacement surgery, and we use this graft in all patients in whom we are replacing a torn ACL unless the patient strongly desires an alternative graft. If the patient has had a prior patellar tendon graft that has failed, we use hamstring tendon autograft for revision surgery, if available. We do not use the accelerated rehabilitation program described herein following revision ACL replacement surgery.

Rehabilitation:

Preoperative protocol

The patient is seen in the office several days before surgery, at which time a preoperative history and physical examination are performed. After the surgeon explains the procedure, the patient watches a video tape detailing the preoperative instructions, surgical procedure, risks, benefits, complications, anesthesia and postoperative course. A physical therapist explains the exercises that will be accomplished during the first week after surgery.

Phase I

Phase I begins immediately after surgery. The doctor applies a continuous passive motion (CPM) machine to the patient’s knee in the operating room, before the patient awakes. The patient remains in the hospital overnight, using the CPM machine continuously. The patient is discharged home the following morning after receiving final instructions on the operation of the CPM machine from a physical therapist. A hinged postoperative brace locked in extension is fitted to be used during ambulation. The patient is allowed to ambulate, full weight bearing, with the postoperative brace in place using crutches.

Phase II – one to five weeks after surgery

At the end of the first postoperative week, the patient returns to the office for suture removal and examination by the surgeon. The postoperative brace is shortened, but the hinges remain locked in extension. The patient is instructed Phase II exercises which will be followed for the next four weeks. Full weight bearing is encouraged, and the postoperative brace and crutches may be used as needed for support and comfort. The patient may progressively discontinue using the crutches and brace as soon as the knee feels strong enough to be stable. Most patients discontinue the brace and crutches at approximately two weeks after surgery. Gait is independent (without brace or crutches) between 3 and 5 weeks postoperatively.

The patient should keep trying to do the quadriceps setting exercise until he or she can lift the limb off the bed without letting the knee flex. Additional exercises include standing hamstring curls for active knee flexion and standing toe raises. The wall slide involves supporting the body against a wall and gently squatting to 30-45. Rounding out the Phase II exercises are side-lying hip abduction, mini-squats from 45 to 60 degrees knee flexion, and the wall slide from 45 to 60 degrees knee flexion.

Phase III – five to nine weeks after surgery

Phase III begins at week five and continues through week nine (Table 3). Swimming may begin at this time, using only the standard freestyle kick, also called the flutter kick. This kick allows only vertical scissoring motion of the legs in the sagittal plane, avoiding rotational movements involved in other kicks (e.g. the breaststroke kick). The strokes that are allowed are the freestyle and backstroke. Swimming with a kick board is allowed as long as the flutter kick is used.

Phase IV – from ten weeks following surgery

From the tenth week forward, the patient is in Phase IV of the accelerated ACL rehabilitation protocol. The goals to be attained in Phase IV are to regain full muscle strength, improve cardiovascular conditioning, and perform sports-specific train-ing.

Discussion

The trend to begin immediate mobilization after ACL replacement surgery with continuous passive motion was first documented in the literature in the early 1980’s (1,7) . Over time, the success with this change in rehabilitation has convinced many orthopaedic surgeons to add early motion in their rehabilitation protocols. (8,15) Often the recovery has been so rapid that athletes have been able to return to play before the graft and/or donor site(s) have healed. In an attempt to push the envelope for return to play, reports of untoward effects such as patella fracture have reached the media. (4,12,14) Experience at both ends of the mobility spectrum has led us to an acceptable timetable for rehabilitation and return to play.

Ample evidence suggests that motion and physiologic loading are essential for proper maintenance and function of articular cartilage. (1) Lengthy immobilization leads to muscle and cartilage atrophy, osteoporosis, and arthrofibrosis. Biomechanical studies suggest that early motion without load bearing will not put the graft or the graft fixation in jeopardy. (16,17)

It is of particular importance to remember that the graft and the patella donor site are probably the weakest at about 3 months. (2,6) This data emphasizes the importance of maintaining motion and continuing strengthening without stressing the graft. Bennyon noted that the anteromedial bundle of the ACL is most stressed towards terminal extension. (4) Because of this, there are some physicians who recommend that patients perform active extension against resistance up to, but not fur-ther than, 40 degrees.

A crucial element of the rehabilitation protocol is regain-ing full extension of the knee. Shelbourne noted that athletes complained of less extremity pain and fatigue after he began emphasizing extension in rehab. (10,11)

Many researchers have noted that open chain kinetic exer-cises markedly increase the shear stresses across the graft, which likely put the graft at risk for stretching or rupture. (3,5,12,13) Closed chain exercises, on the other hand, decrease forces across the patellofemoral joint and all but eliminate shear stress to the tibia, particularly when exercises are performed between 30° and 90° of flexion. (1,7,11,12)

There is evidence to suggest that patients with ACL tears, regardless of whether they have surgery or not, never fully regain quadriceps strength on the affected side. Shelbourne has stated that the best predictor of regaining quadriceps function was a motivated athlete. The most motivated athletes he observed gained 85% to 90% of function at 10 weeks. (9)

Our protocol, unlike the regimens of many other surgeons, minimizes loading of the patellofemoral joint. Patellar tendonitis, anterior knee pain and effusion are common after ACL replacement surgery. We believe that these complications are secondary to some rehabilitation protocols’ reliance on modalities such as stair climbing, lunges and squats for muscle strengthening. Our protocol uses other quadriceps exercises that minimize patellofemoral loading while providing adequate strengthening of the quadriceps muscles. Patients are allowed to discontinue wearing a hinged postoperative knee brace when they have demonstrated good quadriceps strength.

In summary, our rehabilitation protocol following ACL replacement surgery combines early motion with protective strengthening exercises. We have used this protocol for the past five years with all patients who have undergone primary patellar tendon autograft ACL replacement. Since the patients themselves control the amount of flexion during use of the CPM machine, we have encountered very few complications with this accelerated rehabilitation protocol. The goal of this innovative approach is to get the athlete back to playing sports as early and as safely as possible.