ACL Surgery – Allograft vs Autograft

The anterior cruciate ligament reconstruction surgery involves the use of an arthroscope to reconstruct the torn anterior cruciate ligament with graft tissue. Anterior cruciate ligament (ACL) reconstruction is one of the most common orthopedic surgeries. The graft material may either be harvested from the patient’s own body which is known as autograft or from a cadaver known as an allograft.

Postoperative images showing quadriceps tendon autograft scar and range of motion.

The choice of graft material depends upon the patient’s age, level of activity, availability, and the operating surgeon’s expertise. Both types of graft are highly successful and have been in use for the past many years. There are pros and cons associated with each type of graft. The patient is educated regarding the type of graft to be used for their surgery.

Autograft ACL reconstruction

Autograft is harvested from the patient’s own body. The graft is a part of the patient’s body that has the same cellular and tissue makeup. Genetic compatibility ensures that the graft is not rejected by the body’s immune system.

Graft harvestation is the first step in autograft ACL reconstruction. The graft is commonly taken from the patellar tendon along with bone blocks from the patella and the tibia (Bone-Patellar-Tendon-Bone). The BPTB graft along with the bony ends helps in the biological incorporation of the graft. The bone ends naturally fuse with the femur and the tibia as they heal.

A hamstring graft is a soft tissue graft harvested utilizing the tendon of hamstring muscle on the inner aspect of the knee. The tendons are quadrupled to increase their strength. The quadrupled tendon has more strength than the natural ACL.

Other autografts that may be used for ACL reconstruction include the quadriceps tendon and the peroneal tendon. The soft tissue tendon grafts are usually secured in the tunnel for ACL using undo buttons, screws, etc.

While the autograft offers the advantage of being a part of the patient’s own body, it may have a few associated cons. The location of the graft site may not help and cause morbidity. Patellar tendon grafts have been associated with pain located in front of the knee. Similarly, hamstring autograft may cause inhibition of the hamstrings. The hamstrings are required to bend the knee and a tendon graft from the hamstring may cause knee weakness. Similar weakness in straightening the knee may result from quadriceps tendon graft.

Autograft harvesting also increases the operative time of the surgery. The autograft at times may not be of the required thickness and length to substitute the natural ACL. The autograft ACL reconstruction may also prolong the rehabilitation period.

Allograft ACL reconstruction

Allograft anterior cruciate ligament reconstruction involves the use of a graft harvested from a human cadaver. Allograft may be from a cadaveric achilles tendon, tibialis anterior/posterior tendon, hamstrings or patellar tendon.

The allograft is usually irradiated to kill any infectious agent such as bacteria/viruses. The allograft is readily available and comes in different sizes. The allograft shortened the operative time. The allograft also leads to early incorporation in the bone tunnel. Allograft ACL reconstruction also offers the benefit of no graft site morbidity. Participation in rehabilitation and general recovery is faster than autograft.

Allografts however may present a challenge in younger age groups. Allografts in patients aged 30 or less have been associated with early graft failure. The failure may result from the rejection of the cadaveric graft tissue. The body’s immune system may reject the graft and the resulting inflammation may lead to graft failure.

The allograft ACL reconstruction is also considered to be less strong than the autograft reconstruction. The irradiation of the cadaveric graft to kill any infectious agent may also lead to biochemical changes in the structure of the graft that may weaken the integrity of the reconstruction. Although the irradiation kills any infectious agent, there might still be a possibility of transmission of a disease agent.

Summary

Both autograft and allograft are safe options for ACL reconstruction but the ultimate decision for the graft type may depend upon the patient’s needs and anatomy. Discuss the possible options with your orthopedic sports surgeon before surgery.