ACL reconstruction is not an ACL repair. A repair implies that you can fix something that is broken. If an ACL is completely torn, it will not heal back together, even if the torn ends are sewn together. In actuality, the tendon almost always appears frayed when visualized after an ACL tear. What does work well, is to remove the torn ends of the ACL and replace the ligament with a different structure (a graft). To secure the graft into the position of the normal ACL, tunnels are made in the shin bone (tibia) and thigh bone (femur), and the graft is passed through these tunnels to reconstruct the ligament.
The patellar tendon is the structure on the front of your knee that connects the kneecap (patella) to the shin bone (tibia). The patellar tendon averages between 25 to 30 mm in width. When a patellar tendon graft is taken, the central 1/3 of the patellar tendon is removed (about 9 or 10 mm) along with a block of bone at the sites of attachment on the kneecap and tibia.
- Advantages: Many surgeons prefer the patellar tendon graft because it closely resembles what needs reconstruction. The length of the patellar tendon is about the same as the ACL, and the bone ends of the graft can be placed in to the bone where the ACL attaches. This allows for "bone to bone" healing, something many surgeons consider to be stronger than any other healing method.
- Disadvantages: When the patellar tendon graft is taken, a segment of bone is removed from the kneecap, and about 1/3 of the tendon is removed. There is a risk of patellar fracture or patellar tendon rupture following this surgery. Also, the most common problem following this surgery is pain on the front of the knee ("anterior knee pain"). In fact, patients sometimes say they have pain when kneeling, even years after the surgery.
The hamstring muscles are the group of muscles on the back of your thigh. When the hamstring tendons are used in ACL surgery, two of the tendons of these muscles are removed, and "bundled" together to create a new ACL. Over the years, methods of fixing these grafts into place have improved.
- Advantages: The most common problem following ACL surgery using the patellar tendon is pain over the front of the knee. Some of this pain is known to be due to the graft and bone that is removed. 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 less.
- Disadvantages: The primary problem with these grafts is the fixation of the graft in the bone tunnels. When the patellar tendon is used, the bone ends heal to the bone tunnels ("bone to bone" healing). With the hamstring grafts, a longer period of time is necessary for the graft to become rigid. Therefore, people with hamstring grafts are often protected for a longer period of time while the graft heals into place.
Read on for more about cadaver (donor) grafts...