ACL reconstruction surgery and rehabilitation: What exactly is involved in anterior cruciate ligament (ACL) reconstruction?

The anterior cruciate ligament (ACL) has limited ability to form scar tissue and heal. The untreated knee is at risk of instability, meniscal tears and osteoarthritis. There is, however, no evidence that operations reduce the risk of meniscal tears or osteoarthritis. Eighty per cent of non-sporting people function well without an anterior cruciate ligament (ACL). In all cases, the age of the patient, their general activity level, their symptoms, and their expectations must be considered. In some patients conservative treatment may be chosen if their sporting expectations are limited, or if, after a period of intensive rehabilitation, they do not suffer symptomatic instability.

When conservative ACL management fails
Patients with ACL tears who place high demands on their knees, generally require ACL reconstruction. Such demands include the ability to jump, cut, accelerate and decelerate (1). Patients with symptomatic instability and associated meniscal lesions may also require ACL reconstruction. Non-operative management is reserved for the physiologically older patient with a low activity level and minimal or very mild symptoms. Failure of conservative management is an indication for surgical reconstruction.

The absolute indication for operative treatment is symptomatic instability that has failed to improve with an adequate rehabilitation programme. In the chronic anterior-cruciate deficient knee the other ligament supports (the secondary restraints) may begin to give way. Many anterior cruciate ligament (ACL) injuries in this country present late and therefore have laxity of the secondary restraints by the time of surgery. This is most commonly seen in athletes who return to sports without reconstruction and is associated with a high incidence of medial and lateral meniscus injuries. These athletes often say that they can run in a straight line, but any attempt to twist or alter direction causes a feeling of the joint being unstable and giving way.

The two groups
Reconstruction of the ACL is the surgical treatment of choice once direct primary repair of the ligament has been shown to result in persistent laxity and instability of the knee(2). The aim of reconstruction is to restore stability of the knee without restricting its other functions, especially motion.

Reconstruction techniques can be broadly split into two groups:
(i) Extraarticular reconstruction
(ii) Intraarticular reconstruction

Extraarticular reconstruction
Extraarticular reconstruction uses the structures on the lateral side of the knee to mimic the actions of the ACL. For example, by surgically tightening the iliotibial tract, excessive lateral excursion of the tibia is prevented. The overall aim is to prevent anterior subluxation of the lateral tibial plateau in relation to the lateral femoral condyle and to correct anterolateral rotatory instability. The success of extraarticular reconstruction has been limited and as a result the trend has been towards intraarticular reconstructions, and arthroscopically assisted reconstructions in particular. In some centres, extraarticular reconstruction is still favoured in the skeletally immature patient where the physes are still open and fixation across a physis may lead to premature closure of that growth plate — this too is an area of great debate, however(3).

Some orthopaedic surgeons have advocated the use of combined intra and extraarticular reconstructions(4,5). Although there is no evidence to suggest that combined reconstruction techniques improve the clinical outcome, there is evidence indicating that load sharing between the intra and extraarticular elements occurs(6,7).

Intraarticular reconstruction
Intraarticular reconstruction tries to reproduce the anatomic ACL. The donor tendon graft spans the intercondylar notch from the origin to insertion of the ACL. Significant advances in arthroscopic techniques, and very good clinical results, have led to the increased availability and popularity of arthroscopically assisted ACL reconstruction. The most commonly used grafts are bone patellar tendon bone (BPTB) and four stranded hamstring tendons. The results of these are equally satisfactory at five years (8).

Important steps in intraarticular ACL reconstruction
* Once the graft is harvested, it is passed through a tibial tunnel, through the knee joint, and through a femoral tunnel. It is usually secured at either end with compression interference screws or an alternative fixation device. Surgery is now facilitated by the use of jigs, which allow arthroscopic reconstruction.

* Thorough examination of the knee under anaesthetic — particularly to pick up associated instabilities that may lead to premature failure of the reconstruction.

* Diagnostic arthroscopy — to examine the menisci and joint surfaces.

* Meniscal repair or excision

* ACL stump excision

* Lateral superior expansion notch-plasty — expanding the femoral notch to allow accurate graft placement and free motion

* Placement of an appropriately sized tibial tunnel (based on the size of the graft). It should be in the posterior third of the ACL tibial footprint. If the tibial tunnel is positioned anteriorly, extension is restricted and graft impingement may cause early rupture or loss of knee extension.

* Placement of appropriately sized femoral tunnel. It should be at 11 o'clock in the right knee and 1 o'clock in the left knee at the back of the intercondylar notch when viewed arthroscopically. If the femoral tunnel is positioned anteriorly, flexion is restricted which may cause a loss of motion or graft failure due to stretching.

* Secure fixation of the graft in both tunnels, usually using interference screws, although there are more and more fixation devices available. These are usually left in permanently.

* Evaluation of the graft fixation, stability, and impingement-free range of motion.

* Standard wound closure

Some units will perform this procedure as daycase surgery. This, however, also necessitates extensive pre- and post-operative visits to learn about the procedure and about the post-operative rehabilitation. Most units will admit the patient the day prior to surgery and will allow discharge within 24-48 hours of surgery once pain control is achieved and knee swelling has started to settle down.

Timing of surgery
The goals of surgery are to obtain a stable knee, to eliminate the pivot shift, to protect the menisci, to regain a full range of movement, to avoid patello-femoral problems, and to ensure a return to sporting activity. Prior to surgery, the patient's age, previous level of activity, both recreational and occupational, expectations of future activity, motivation and ability to participate in a thorough rehabilitation programme should be carefully evaluated. Moreover, the patient who already has meniscal or chondral damage, or has knee pain secondary to early degenerative changes should be warned that ACL reconstruction provides stability without necessarily giving relief of pain.

Surgery should always be deferred until a range of movement of at least 0-120 degrees is obtained in a knee that is quiet and non-inflamed. This usually means a delay of up to six weeks from the time of injury. This decreases the risk of arthrofibrosis and post-operative knee stiffness.

The general consensus is that it is sensible to wait until the initial inflammatory response to the injury has subsided and a full range of movement has returned before the ACL is reconstructed(9,10,11). Early ACL reconstruction, especially in patients with medial collateral ligament injury and/or extraarticular surgery, is associated with an increased incidence of arthrofibrosis — joint stiffness that can be permanent and require further surgery(2). Exceptions are often made when other ligaments that require repair are also injured, for example in the dislocated knee scenario.

The debate over whether early ACL reconstruction is justified is ongoing. The theory is that early reconstruction of the ACL when the rest of the knee is normal can reduce the likelihood of subsequent meniscal damage and therefore slow the progression of radiographic osteoarthritic changes(12,13). However, as yet, no studies have shown that reconstructed knees develop less osteoarthritis than those that are treated conservatively.

The presence of an unstable and repairable meniscal lesion combined with ACL insufficiency is a strong indication for early combined ACL reconstruction and meniscal repair(14,15). Arthroscopic relooks performed by Barber et al in 1997(16), suggest that meniscal healing is more successful when the repair is combined with ACL reconstruction (92% success) than without it (67% success).

Rehabilitation
Several studies demonstrate that accelerated rehabilitation emphasising immediate full range of motion, early full weight bearing, strength training, and an early introduction to closed chain exercises, allows a prompt resumption of activities of daily living and sport. The exercises employed in 'accelerated' rehabilitation programmes are known to produce the least strain in the graft(17,18). Such programmes follow graduated protocols which are tailored to the patient's needs and progress. The immediate return to full hyperextension and early functional activity have not been shown to be detrimental to the long-term stability of the knee joint(19,20) and avoid joint stiffness.

The length of time off work will depend on the patient's occupation. A return to sedentary tasks is possible within a fortnight, particularly if the patient is able to get to work using crutches. More manual occupations will require at least three months off work. A significant amount of time off work is necessary in any case to allow for the intensive rehabilitation necessary in these cases.

Usually a patient returns to activities of normal daily living within a few weeks and sports by six months post surgery. Once the patient has regained power greater than 75% of the unaffected leg, strength training is intensified and he/she may begin activities such as straight-line jogging and more sports-specific type training at low intensity.

It is not until patients have regained complete quadriceps and hamstring strength equal to or greater than the other leg, that they are allowed to return to higher intensity sports specific training.

There appears to be no significant benefit in terms of patient recovery for overprotection with plasters/braces or restriction of movement. There is also very little evidence for the use of continuous passive motion (CPM) machines or cryotherapy (which we nevertheless find most patients like)(21,22,23,24).

Complications of ACL reconstruction
These are less than 5% in specialist units with well-organised rehabilitation programmes. Donor-site complications from graft harvest will be discussed in a separate article. Arthroscopic ACL reconstruction is, however, a highly demanding procedure with the possible risk of significant knee disability if the ACL graft is placed, tensioned or fixed incorrectly. There is considerable debate as to whether all surgeons should be performing this procedure, or merely those with an interest in knee surgery. The most common reason for failure of the ACL reconstruction is believed to be technical error. Proper patient selection, surgical technique and postoperative rehabilitation remain the foundations for successful ACL reconstruction. Care must be taken at every step of the process to ensure graft failure does not occur because revision ACL surgery results are not as predictable as those of primary procedures.

Success rates
Reconstruction of the anterior cruciate ligament (ACL) tendon-bone has been demonstrated in numerous series to be a valuable procedure which abolishes instability and improves performance in 90% or more of patients over a five year period. Great motivation is required for satisfactory rehabilitation.

Alex Watson and Fares Haddad

References
(1) Sports Injury Bulletin, 1 (9), pp1-3, 2001
(2) Orthopaedic Review, 22 (11), pp1213-1223, 1993
(3) Instructional Course Lectures, 47, pp351-359, 1998
(4) Journal of Bone and Joint Surgery, B73 (3), pp368-373, 1991
(5) Annals of the Royal College of Surgeons, 77 (4), pp290-298, 1995
(6) American Journal of Sports Medicine, 18 (3), pp262-266, 1990
(7) American Journal of Sports Medicine, 18 (2), pp169-176, 1990
(8) American Journal of Sports Medicine, 28 (1), pp124-130, 2000
(9) American Journal of Sports Medicine, 23 (1), pp87-92, 1995
(10) American Journal of Sports Medicine, 20 (5), pp499-505, 1992
(11) American Journal of Sports Medicine, 21 (3), pp338-347, 1993
(12) Clin Orthop, 358, pp188-193, 1999
(13) American Journal of Sports Medicine, 28 (4), pp446-452, 2000
(14) Clin Orthop, 283, pp207-214, 1992
(15) Clin Orthop, 252, pp55-63, 1990
(16) Arthroscopy, 13 (4), pp433-437, 1997
(17) American Journal of Sports Medicine, 23 (1), pp24-27, 1995
(18) American Journal of Sports Medicine, 23 (4), pp401-406, 1995
(19) American Journal of Sports Medicine, 27 (1), pp84-93, 1999
(20) American Journal of Sports Medicine, 27 (2), pp156-161, 1999
(21) Arthroscopy, 7 (1), pp39-44, 1991
(22) Knee Surg, Sports Trauma, Arthroscopy, 1 (2), pp68-70, 1993
(23) American Journal of Sports Medicine, 23 (5), pp24-27, 1995
(24) American Journal of Sports Medicine, 27 (1), pp76-83, 1999