In the sports world, knee injuries are a common problem, especially torn anterior cruciate ligaments (ACLs). The ACL crisscrosses with another ligament inside the knee. These two ligaments hold the two major bones of the leg together. If either one of these ligaments gets torn, the knee can become unstable. An unstable knee joint can cause the leg to feel unsteady or possibly give out. In such cases, walking can be difficult, and playing sports may be impossible.
Doctors can repair the ligament by replacing it with a piece of similar tissue taken from another part of the leg. The place where the replacement tissue comes from is called the “donor site.” Several donor sites have been used to repair the ACL, including the patellar tendon, quadriceps tendon, hamstring tendon, or the iliotibial band. Patellar and quadriceps tendon tissue comes from the front of the knee. Hamstring tendon is taken from the back of the knee. Iliotibial tissue comes from the outside of the knee.
When doctors use more than one method to repair a single injury, it is important to keep track of which way works best. Researchers can report successful trends by reviewing all the reports available. In the case of ACL repair, doctors want to know: Which donor site holds up the best? Which donor site has the fewest problems years later?
After looking over many medical studies of ACL repairs, researchers noticed the following:
- Problems at the donor site and knee pain are the two biggest problems after ACL surgery, no matter where the donor tissue comes from.
- Small nerves can be injured during surgery, causing pain or loss of sensation at the donor site.
- There aren’t enough reports to compare all four kinds of donor-site grafts. Comparing just hamstring grafts to patellar tendon grafts shows fewer problems when the hamstring tendon is the donor tissue.
- No matter where the graft tissue comes from, it is important to get full knee motion and normal strength back in order to avoid future knee problems.
- Using patellar tendon grafts from the front of the knee results in difficulty kneeling about half of the time.
All things considered, using the hamstring tendon to replace a torn ACL has the best result. When donor tissue comes from the back of the knee, there are fewer problems with kneeling. The removed hamstring tendon regrows (at least partially) with normal tissue within two years. Regrowth of tissue removed from the front of the knee is slower and leaves a larger gap.
When taking tissue from different places to repair a torn ACL, doctors look at short- and long-term problems that occur at the donor site. They also examine the knee after surgery and compare motion, strength, and return to activities as measures of success. More information is needed before the overall best method for repairing the torn ACL can be decided.