How ACL Surgery Is Performed

Surgeons working

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ACL tears are a common sports injury that often requires surgical treatment. Once you have decided to proceed with ACL surgery, you have committed to having your anterior cruciate ligament (ACL) reconstructed in your knee joint. Learn the steps of ACL surgery, and how an ACL is made and secured within your knee joint.

Determine the Type of ACL Graft

There are three types of ACL grafts most commonly used. These include patellar tendon, hamstring tendon, and allografts (donor) grafts. A fourth type graft type less commonly used is the quadricepts tendon graft. There are various pros and cons of each type of graft, and deciding on which is best for you can be a difficult decision.

Diagnostic Arthroscopic Surgery

The first step of surgery is to insert an arthroscope into the knee joint to inspect the damage done to the joint. Your doctor will confirm the diagnosis of the ACL tear, and also inspect for other damage. The meniscus, cartilage, and other ligaments can be inspected for damage that may have occurred. It is common to treat meniscus tears and cartilage injuries at the same time as performing ACL reconstruction.

'Harvest' and Prepare the ACL Graft

Once the ACL tear is confirmed, the graft must be obtained, a process called "harvesting" the graft. In the case of a donor graft, the tissue must be thawed. In cases where the graft is coming from the patient having the ACL reconstruction, an incision will be made to obtain the tissue.

After obtaining the graft, the tissue being used to create a new ACL is prepared to be the proper length and width. Some trimming may be performed to ensure the proper size of the graft. The graft is then set aside until the knee is ready for the new ACL.

Tibial Tunnel

The next step is to create a place for the new ACL to sit within the knee. The ACL is right in the center of the knee joint and needs to be attached to the bone above and below the joint. Therefore, the new ligament must start within the end of the thigh bone and end within the top of the shin bone.

A drill is used to make a tunnel in the shin bone. The end of this tunnel in the knee joint is directly where the ACL should attach to the shin bone.

Femoral Tunnel

Through the tibial tunnel just created, a drill is passed directly through the middle of the knee joint. A second bone tunnel is made from inside the knee up into the end of the femur. This bone tunnel will hold one end of the new ACL, and the tibial tunnel will hold the other.

Pass the Graft

With two bone tunnels—one at the end of the femur, and another in the top of the tibia—the new ACL graft must be passed into position. A large pin is passed through both bone tunnels, and attached to the end of the pin is the new ACL. The new ACL is pulled up into the femoral tunnel so one end can be secured into the femur. The other end is now in the tibial tunnel, and the central portion of the graft is in the center of the knee joint taking the place of the old ACL.

Secure Femoral Side of Graft

With the ACL graft in position, the graft must be solidly fixed in its new position. There are several ways to secure the graft. One common way to do so is to use a screw to hold the graft end within the tunnel. The screw can be made of metal, a plastic-dissolvable material, or a calcium-based substance that turns into bone. Your doctor may recommend a particular type of material, although none has been shown to be "better" at securing the graft.

Secure Tibial Side of Graft

Once the graft is solidly fixed on the femoral side, tension is placed on the end of the graft so the new ACL will be tight. The tibial side of the new ligament is then fixed, similarly to the femoral side. Again, different materials may be used to fix the graft into position. Over time, the graft will heal to the surrounding bone, making the fixation devices unnecessary. Occasionally, a prominent screw or staple that was used to hold the graft in the position may be removed after about a year. If not causing problems, these materials are usually left in place.

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