Types of ACL Grafts

The ACL is the most commonly reconstructed ligament of the knee because injury to the ligament can result in significant instability and impairment of knee function (5). There are three main types of grafts used for creating a replacement ACL: patellar tendon or semitendinosus-gracilis (hamstring) tendon autografts and cadaver allografts. An autograft simply refers to harvesting the patient's own tissue and an allograft is tissue from another individual.

Patellar Tendon

The first graft method uses a patellar tendon autograft, which connects the patella and tibia. This tissue is actually a ligament because it connects bone to bone. The middle third of the ligament is cut out, harvesting a small portion of bone from both the patella and tibia. The advantage of this reconstruction is that it is considered a very strong donor material and is likely to withstand strong future stresses after proper rehabilitation. Also, in contrast to other graft methods, when using an autograft there is no chance of an immune system rejection (5). A disadvantage of this method of repair is sensitivity of the patella and tibia where the bone was removed. During recovery, some patients experience more soreness and pain come from the harvested patellar tendon instead of the reconstructed ACL. This increased recovery time may delay a patient's return to full pre-injury ability, and may limit full knee extension and increase the likelihood of a patella fracture. No loss of quadriceps or hamstring strength has been noted (5).

Hamstring

The second graft method is another autograft that harvests the semitendinosus-gracilis (hamstring) tendons, which connect muscle of the back of the thigh to the lower leg. Two small portions of these tendons are removed and looped together to form a strong tissue graft for ACL reconstruction. The tendons can either be braided together or stitched as double or quadrupled grafts to gain this strength. The most common problem following ACL surgery using the patellar tendon is pain over the front of the knee. This is not a problem when using the hamstring tendon. The incision is also smaller, and the pain both in the immediate post-operative period, and down the road, is thought to be lesser than for patellar tendon graft (5). A much quicker recovery has been seen with the hamstring grafts. However, one disadvantage is a reduction in strength in the hamstring muscles after reconstruction. Furthermore, since neither end of the hamstring graft contains bone, it takes much longer for the graft to become secure within the knee.

Cadaver

Finally, cadaver allografts are another viable option. Allograft means from another person; in most cases the graft is another person's patellar tendon. Recovery time is the shortest with this method because the patient is not also recovering from patellar tendon or semitendinosus-gracilis invention. However, the major disadvantage with cadaver grafts is the possibility for graft rejection even fifteen years following the operation. Also, some patients may feel uneasy about using tissue not their own. This method many times is used with older patients that do not necessitate heavy physical activity, or whom want to avoid extraneous rehabilitation (6).

Obviously pain and strength are the most important factors post-ACL reconstruction. For patients heavily involved in sports such as gymnastics and football, hamstring strength is of the utmost importance and patellar tendon graft may be the best choice (5). However for other individuals, hamstring grafts may be best. For example carpet layers may want to prevent anterior knee pain associated with patella tendon grafts or basketball players may want to make sure to maintain their full knee extensor mechanism (5).

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