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Where does the new ligament come from?

Once you have decided to have your ACL surgically reconstructed you should talk to your surgeon about how he or she performs the surgery and what type of graft he/she likes to use to reconstruct a torn ACL. During this surgical procedure, the remnants of your torn ACL need to be removed, and a similar ligament from somewhere else around your knee needs to be inserted in the place of the original ACL.

Using a ligament from somewhere else around your knee may sound a bit like robbing Peter to pay Paul, and in fact it is, for each of the grafts that are used for ACL surgery has some drawbacks. The grafts that are currently used today are the central part of the patellar tendon, some of the hamstring tendons, or an "allograft" from a cadaver. The advantages and disadvantages of these grafts are explained:Patellar tendon graft (Image Credit: Seif Medical Graphics)


Patellar tendon -- for this type of graft, the central 1/3 of the patellar tendon is removed along with a small block of bone at each end of the ligament. This creates a bone-patellar tendon-bone graft. Some surgeons favor this graft because it was the first successful graft to be used in modern ACL surgery, and the bone blocks at either end are designed to allow the graft to be securely fixed and heal quickly inside tunnels drilled in the femur and tibia. The patellar tendon connects the patella to the tibia and is the tendon that allows the quadriceps muscle to extend the knee. Removing a graft from the center of the patellar tendon can result in inflammation of the tendon which can lead to patellar tendinitis and anterior knee pain after surgery in some people.


Hamstring tendon graft (Image Credit: Seif Medical Graphics)

Hamstring tendon -- the gracilis and semitendinosus muscles, which are part of the hamstrings that help to flex your knee, have long tendons that insert into the tibia just below the level of your knee joint. These tendons can be removed, doubled over, and then used to replace the ACL. These tendons are easier to harvest than the patellar tendon, they require smaller drill holes in the femur and the tibia for fixation, and they do not predispose patients to patellar tendinitis. Most athletes never notice any decrease in strength or agility after their hamstrings have been harvested. The drawback to this procedure, however, is that hamstring grafts are more challenging to anchor in the femur and tibia because they do not have blocks of bone at either end.


Allograft -- a frozen piece of the patellar tendon from a human who has donated his or her tissue to a tissue bank can also be used to reconstruct the ACL. Using this graft has the obvious advantage of avoiding harvesting either the patellar tendon or the hamstring tendons from the patient. The entire surgical procedure can be done much faster. However, using this type of a graft carries a very small risk of infection and the rate of graft failure, or re-rupture, is probably higher than with the use of the other two types of grafts.

Several factors influence what type of graft may be the best choice for you and your surgeon. If you have a history of patellar tendinitis or patellofemoral pain, or if you happen to have a very narrow or very short patellar tendon, then a hamstring tendon graft may be necessary for you. However, if the hamstring tendons are too small or not strong enough to replace the ACL you may require either a patellar tendon graft or allograft. Most surgeons develop a preference for one type of graft versus the others. The graft that your surgeon chooses may be influenced by the practice prevailing where he trained, but he might employ any of a number of alternative techniques as well. While there is a lot of scientific debate at the moment about what type of graft is the best, there is no clear answer to that question. Each graft certainly has its place in today's surgical reconstruction techniques. Across the United States today, most surgeries are done with hamstring or patellar tendon grafts.


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