Anterior cruciate ligament reconstruction (ACL reconstruction) is a surgical tissue graft replacement of the anterior cruciate ligament, located in the knee, to restore its function after an injury. The torn ligament can either be removed from the knee (most common), or preserved (where the graft is passed inside the preserved ruptured native ligament) before reconstruction through an arthroscopic procedure. ACL repair is also a surgical option. This involves repairing the ACL by re-attaching it, instead of performing a reconstruction. Theoretical advantages of repair include faster recovery and a lack of donor site morbidity, but randomised controlled trials and long-term data regarding re-rupture rates using contemporary surgical techniques are lacking.
Background
The Anterior Cruciate Ligament is the ligament that keeps the knee stable. Anterior Cruciate Ligament damage is a very common injury, especially among athletes. Anterior Cruciate Ligament Reconstruction (ACL) surgery is a common intervention. 1 in every 3,000 American ruptures their ACL and between 100,000 and 300,000 reconstruction surgeries will be performed each year in the United States. Around $500 million health care dollar will come from ACL injuries. ACL injuries can be categorized into groups- contact and non-contact based on the nature of the injury Contact injuries occur when a person or object come into contact with the knee causing the ligament to tear. However, non-contact tears typically occur during the following movements: decelerating, cutting, or landing from a jump. ACL injury is 4-6 times higher in females than in males. ACL injuries account for a quarter of all knee injuries in the high school population. An increased Q angle and hormonal differences are a few examples of the gender disparity in ACL tear rates.
Types of grafts
Graft options for ACL reconstruction include:
Autografts (employing bone or tissue harvested from the patient's body). Allografts (using bone or tissue from another body, either a cadaver or a live donor). Bridge-enhanced ACL repair (using a bio-engineered bridging scaffold injected with the patient's own blood). Synthetic tissue for ACL reconstruction has also been developed, but little data exists on its strength and reliability.
Autograft
An accessory hamstring or part of the patellar ligament are the most common donor tissues used in autografts. While originally less commonly utilized, the quadriceps tendon has become a more popular graft.
Because the tissue used in an autograft is the patient's own, the risk of rejection is minimal. The retear rate in young, active individuals has been shown to be lower when using autograft as compared to allograft.
Hamstring tendon
Hamstring autografts are made with the semitendinosus tendon, either alone or accompanied by the gracilis tendon for a stronger graft. The semitendinosus is an accessory hamstring (the primary hamstrings are left intact), and the gracilis is not a hamstring, but an accessory adductor (the primary adductors are left intact as well). The two tendons are commonly combined and referred to as a four-strand hamstring graft, made by a long piece (about 25 cm) removed from each tendon. The tendon segments are folded and braided together to form a tendon of quadruple thickness for the graft. The braided segment is threaded through the heads of the tibia and femur, and its ends are fixed with screws on the opposite sides of the two bones.
Unlike the patellar ligament, the hamstring tendon's fixation to the bone can be affected by motion after surgery. Therefore, a brace is often used to immobilize the knee for one to two weeks. Evidence suggests that the hamstring tendon graft does as well, or nearly as well, as the patellar ligament graft in the long term. A Cochrane review in 2011 found insufficient evidence to suggest whether a hamstring versus patellar ligament graft was superior. It found that individuals receiving hamstring autografts had reduced flexion (bending knee) range of motion and strength. Common problems during recovery include strengthening of the quadriceps, IT-band, and calf muscles.
The main surgical wound is over the upper proximal tibia, which prevents the typical pain experienced when kneeling after surgery. The wound is typically smaller than that of a patellar ligament graft, and so causes less post-operative pain. Another option first described in 2004, a minimally invasive technique for harvesting from the back of the knee, is faster, produces a significantly smaller wound, avoids the complications of graft harvesting from the anterior incision, and decreases the risk of nerve injury.