Hamstring Tendon Graft

Interference screws with special threads designed not to cut the hamstring tendons are now able to fix the tendon within the bone tunnel similar to the patellar tendon bone fixation. One of the screw types comes impregnated with hydroxyapetite (HA), a bone growth stimulant, to encourage both resorption of the screw as well as stimulate bone growth into the graft. Fixation of the graft within the bone tunnel itself effectively shortens the functional length of the soft tissue graft, thereby reducing the "bungee effect". It will further support the fixation by tying the ends of the graft with sutures over a screw post or staple.

Advantages

Hamstring grafts require a smaller incision and are less painful to harvest. Thus the initial postoperative period is often easier and more comfortable with this graft choice. Similarly, because there is no violation of the patellar tendon, there seem to be fewer problems with knee pain during the first few months that a patient is allowed to return to sports. The hamstring incision is away from the patella so patients are usually comfortable kneeling.

Because the quadriceps extensor mechanism isn't violated with a hamstring harvest there is often less initial quadriceps atrophy (wasting muscle loss). With a quicker return of knee quadriceps strength, there may be a chance for fully recovered patients to return to sports a month or two earlier than they might for a patellar tendon BTB graft.

In younger patients who have torn their ACL's but still have open growth plates; the hamstring tendon graft is a good choice. This is because there are no graft bone ends that could bridge the growth plates and lead to premature closure or arrest of the bone. Premature growth plate closure can result in angular deformities or shortening of the limb.

Disadvantages

Although the fixation techniques are quite good, hamstring tendon grafts still ultimately rely on soft tissue-to-bone healing. Soft tissue-to-bone healing occurs at a slower rate than bone-to-bone healing. A rare occurrence known as tunnel widening is sometimes seen as early as 3 months after hamstring graft ACL reconstruction. This is a condition where the x-ray views of the reconstructed knee show that the original borders of the bone tunnels in the femur and/or the tibia expand out or enlarge. Although this process is by no means unique to hamstring tendon grafts, there is definitely a higher incidence with these grafts.

Another disadvantage of hamstring tendon grafts is that harvesting them is a technically demanding procedure that requires considerable surgical experience. Cutting a tendon in half or injuring nerves or ligaments in the area of dissection are possible during the stripping process. There is also a different technique for tensioning the hamstring tendon in the knee once the femoral end has been secured.