Anterior cruciate ligament (ACL) is one of the four main ligaments of the knee joint, connecting femoral bone to tibia. It is situated in the centre of the joint and prevents excessive anterior displacement of tibia in relation to the femoral bone, while preserving joint stability during rotatory movements.
ACL tears are a common type of injury. They usually affect people who engage in sports, especially football, basketball and skiing, but they can also happen in the context of day-to-day activities. The mechanism of injury in the majority of cases involves a pivoting movement in combination with sudden planting of the leg, false step or landing on an uneven surface after a jump.
In more than half of the cases, ACL tears are accompanied by injuries to other articular elements (usually the medial meniscus and / or the internal lateral ligament). Women appear to be more prone to ACL ruptures, which is attributed to differences in muscle strength, neuromuscular control and loosening of ligaments relative to men.
Immediately after the injury, patients feel joint pain, have swelling, and may experience knee instability (feeling that the knee is “giving”). Diagnosis is usually made based on clinical examination if the rupture is complete. Confirmation is by magnetic resonance imaging (MRI), which is the diagnostic test of choice.
Conservative treatment is preferred in only a few cases where the ACL tear is partial and the joint does not present serious instability.
In these cases appropriate protocols of physiotherapy and progressive rehabilitation are applied, aiming at femoral muscle (especially posterior muscles) strengthening and neuromuscular training of patients, so as to prevent instability. The rehabilitation program usually has a duration of three months.
In the case of professional athletes, patients wishing to participate in high intensity sports and workers who subject the joint to significant stress, the rupture of the anterior cruciate is treated surgically.
The goal is to restore the function of the ACL and maintain joint stability. Suturing of the ACL ruptured ends has not shown good results so far, while open surgery (arthrotomy and restoration under direct vision) has virtually been abandoned.
The treatment of choice is arthroscopic reconstruction with a graft that replaces the injured ACL.
During the operation other structures of the knee, that have been injured along with the ACL, may also have to be repaired (e.g. menisci, articular cartilage, posterior cruciate ligament), with very good results.
The operation is usually performed under general anesthesia and in two stages – arthroscopy and retrieval of the autograft (the graft comes from the patient), if this is what has been decided. The arthroscopy includes endoscopy of the knee, removal of the torn ACL stump, repair of menisci and cartilage injuries and insertion and stabilization of the graft. All of these repairs are performed by insertion of arthroscope and instruments through small incisions (about 1 cm) on the anterior surface of the joint.
The choice of graft to be used takes into account patient characteristics, such as degree of activity, anatomical considerations and surgeon preferences.
Through a small incision on the anteromedial surface of the upper part of the tibia the surgeon removes the tendons of semi-tendinosus and gracilis muscles. The tendons are folded into a quadruple-stranded graft and then pulled into place through bone tunnels in the tibia and thigh and stabilized with special materials. The hamstring graft is the strongest graft for ACL reconstruction (it is stronger than healthy ACL), with low level of postoperative pain and faster recovery.
It is the one more often used in revision surgery, that is operations for replacement of an already existing graft. The middle third of the patellar tendon is taken along with a small bony part of its insertion in the patella and the tibia. This technique is often followed by persisting pain on the anterior surface of the knee and pain at kneeling.
These are rarely used, usually in patients with previous, failed ACL reconstruction surgery or in case of multi-ligamentous knee injury. Their advantage is that, as no autograft is harvested, the operation is of shorter duration and the danger of persisting postoperative pain and muscle weakness is practically eliminated. On the other hand, these grafts are more costly and have higher rates of failure and infection.
Rehabilitation after ACL reconstruction begins on the first postoperative day with physiotherapy. The usual protocols include icing and analgesics during the first postoperative days, muscle strengthening and exercises to increase range of motion and weight bearing. Crutches and functional knee brace. Return to sports or strenuous work is personalized depending on the severity of the injury, the type of treatment, the course of rehabilitation and the compliance of the patient with the instructions of doctors and physiotherapists. In most cases a time period of four to six months is required before the patient returns to previous level of activity.