Articles

Kambiz Behzadi, MD

Introduction 

The anterior cruciate ligament is a vital link in maintaining the normal biomechanical function of the knee. It is now obvious that loss of the anterior cruciate ligament not only produces abnormal knee motions but that it also frequently results in major degenerative changes in the knee. Simple repair of a torn anterior cruciate ligament most often results in an unsatisfactory outcome. In the recent years, many studies involving the anatomy, biomechanics and healing of the anterior cruciate ligament have resulted in improved techniques and identified procedures that re-establish a functional ligament.

The diagnosis of a disruption of the anterior cruciate ligament must be followed by a decision-making process to establish a regimen of treatment that will meet the patient's needs most satisfactorily. No single protocol is applicable to all patients. The final decision must be based on many variables that are unique for each individual. Initially, it must be decided whether operative or non-operative treatment is indicated. Among the factors to be considered are the acuteness of the injury, the presence or absence of other lesions involving the knee (such as cartilage tears), the age and level of activity of the patient, the degree of instability and the ability of the patient to comply with the therapeutic program.

Interval from Injury to Operation

Recent reports have demonstrated that operations on the anterior cruciate ligament are more likely to be complicated by postoperative scarring and stiffness if it is done while the knee is acutely inflamed and the range of motion restricted. Thus, initial treatment must include administration of non-steroidal anti-inflammatory medications, application of ice, and institution of range of motion exercises. Operative intervention can proceed once a nearly normal range of motion has returned and the swelling has been eliminated (generally 2 to 3 weeks after injury). The operation can be postponed until a convenient time for the patient (that is, it can be done during a school break, a vacation from work, and so on). A delay is not detrimental if the patient avoids activities that might cause re-injury and additional damage to the joint. 

Association with Other Injuries

It is generally agreed that an isolated rupture of the anterior cruciate ligament is probably physiologically impossible. However, this ligament can be destroyed without major damage to other ligaments or capsular structures. Most authors have agreed that injury to other major ligaments increases the likelihood that non-operative treatment of the anterior cruciate ligament will lead to unsatisfactory results. Thus, most have advocated reconstruction of the anterior cruciate ligament in these circumstances. 

The most common associated ligament injury is that of the medial collateral ligament. Most medial collateral ligament injuries are partial tears and can be treated without additional surgery, since they heal well with restoration of the anterior cruciate ligament alone. Injury to one or both menisci (cartilage pads between the femur and the tibia) frequently is associated with a complete tear of the anterior cruciate ligament. When a repairable meniscal lesion is observed in association with a complete tear of the anterior cruciate ligament, suture repair of the meniscal lesion is performed. Reconstruction of the anterior cruciate ligament is imperative to protect the meniscal repair. Bone lesions such as "bone contusions" or "micro fractures" as they are called commonly occur with anterior cruciate ligament tears. These generally are treated non-operatively and go on to heal. Their importance and the effect they have on the long-term results have not yet been established. 

Superficial or partial erosions of the joint articular cartilage are sometimes associated with tears of the anterior cruciate ligament. They are more frequent and severe in patients who have a chronic tear. The presence of these erosions has not been proved to be associated with a poor recovery after operations of the anterior cruciate ligament, although these lesions have been shown to accelerate arthritic changes in the knee. Chronic pain caused by advanced arthritis will not be relieved by a reconstruction of the anterior cruciate ligament and this type of surgery is not indicated in patients with advanced arthritis.

Lifestyle

The patient's level of activity is probably the single most important factor in the decision concerning the appropriate treatment of a complete tear of the anterior cruciate ligament. Participants in vigorous sports or work-related activities that involve jumping, cutting, quick starts and stops, and heavy contact will probably have repeated episodes of instability unless they alter this lifestyle markedly. People who have a less demanding level of activity often need to change their lifestyle only slightly, if at all, after an injury to the anterior cruciate ligament. They often are able to avoid activities that might cause re-injury. 

Non-operative treatment may be best for people who are willing to change from a high-risk to a low-risk lifestyle. An athlete can try returning to participation without modifying his or her technique, but the costs of the frequent re-injuries are too high, often leading to marked arthritic changes. The use of sport braces to avoid surgery have not been shown to change this poor outcome in active patients. Rehabilitation of the muscles about the knee (hamstring and quadriceps muscles) is an important part of a successful non-operative treatment.

Operative Restoration of the Anterior Cruciate Ligament

The state of the art technique is that of an arthroscopically assisted ligament reconstruction. This requires several small incisions around the joint for insertion of the arthroscopic instruments and obtaining the tendons that will be used as the graft. The advantages of performing the procedure arthroscopically are numerous. However, the most important point is that the arthroscope provides far superior visualization of the entire joint and its anatomic structures and alleviates the need for an extensive open incision. 

Reconstruction of the anterior cruciate ligament can be performed with many types of grafts. Currently most surgeons prefer reconstruction with an autogenous graft (the person's own tissue). The two most common sources of the autogenous graft are 1) portions of the hamstring tendons, and 2) part of the patellar tendon with attached bone plugs from tibia and patella.

Rehabilitation after Reconstruction of the Anterior Cruciate Ligament

It is universally accepted that post-operative rehabilitation is very important to the outcome of the reconstructive procedures on the knee. Many different programs have been advocated for the rehabilitation of the muscles after repair of the ligaments of the knee. Advocates of aggressive rehabilitation have not reported detrimental effects from early activity of the muscles but there is no doubt that the reconstructed ligaments are vulnerable to overloading if the program of rehabilitation is too aggressive.  

Braces that allow a gradual increase in motion of the knee are often used. The use of stronger material for grafts and better techniques for fixation in recent years have eliminated the need for prolonged immobilization. We firmly believe in the principles of early motion and aggressive muscle stimulation to allow an earlier return to function. Generally patients are able to return to sports in six months after their surgery.

Types of Autogenous Grafts

There are advantages to both sources. The primary advantage to the use of hamstring tendons are their great strength, their easy availability, the ease with which immediate and strong fixation can be achieved, and their versatility to be used in both primary and revision surgery. Also, harvesting of the hamstring tendon is less difficult and with fewer complications than preparation of the bone-patellar tendon-bone grafts. The primary disadvantage of using the hamstring graft is the increased time required for the tendons to heal to the bone tunnels. This generally requires 8 to 12 weeks in comparison to the 6 weeks required for bone to bone healing. The bone-patellar tendon-bone grafts are also a popular graft source. 

Some have suggested that the patellar tendon graft is a stronger tissue than the hamstrings grafts. However, review of most recent literature shows without a doubt that the hamstring grafts as currently used (quadrupled strands) have by far superior strength (in excess of 200% of normal anterior cruciate ligament) as compared to patellar tendon autograft (~120% of normal anterior cruciate ligament). 

The patellar tendon grafts also have certain disadvantages. Post-operative kneecap pain can and does occur more frequently than with hamstring tendons. Patellar tendonitis also occurs more frequently and can be a career-ending complication. Damage to the patellar tendon, quadriceps weakness, and less frequently, fractures of the knee cap are also seen with the use of the patellar tendon grafts. 

It is for these reasons, most notably the long-term excellent results achieved with hamstring tendons, and the increased incidence of knee stiffness and post-operative kneecap pain seen in patellar tendon grafts, that many surgeons are turning to hamstring tendons as the graft of choice in the anterior cruciate ligament reconstruction.

^ back to top