Response of hamstring and patellar tendon grafts for anterior cruciate ligament reconstruction during cyclic tensile loading.

The efficacy of anterior cruciate ligament (ACL) reconstruction in the knee using hamstring tendon or patellar tendon grafts is thought to depend on the relative amounts of graft elongation, or creep, following postoperative rehabilitation. In this study, the creep responses of the tendinous portions of these two graft types were compared during 1 hour of cyclic loading to 200 N at 1 Hz. In the hamstring tendon grafts, strains were measured in both the tissue and in the length-augmentation tape to identify the relative contribution of this particular graft fixation to overall creep. Differences in tissue strain between graft types during cyclic loading were not statistically significant. For both types of grafts, overall graft length significantly increased after 3600 cycles while tissue creep was not significant. The greatest creep in the hamstring tendon grafts occurred at the tissue-tape interface, indicating a potential disadvantage of this composite graft construct.