Many studies have been done to compare these two methods of anterior cruciate ligament (ACL) repair. The hamstring tendon repair has gained in popularity with surgeons because it is easy to harvest. Usually the semitendinosus (ST) portion of the hamstrings is the donor tendon.
With patellar-tendon grafts, there can be pain and loss of function when kneeling.There are fewer problems at the donor site after the operation when the ST tendon is used. A recent study highlighted one disadvantage to the ST donor site.
Loss of strength during deep knee flexion has been reported when using the ST tendon instead of the patellar tendon. Measurements of strength with the knee bent to 45- and 90-degrees showed a loss of torque (force) at 90 degrees (full squat position).
The strength deficit was only shown in patients whose ST tendon reattached above the knee joint or who did not have tendon regeneration seen on MRI. Most patients had full regeneration and full recovery.