Analysis of a semitendinosus autograft in a rabbit model.

The purpose of this study was to evaluate the histologic and biomechanical changes that occur between 12 and 52 weeks in an intraarticular, semitendinosus autograft placed through tibial and femoral drill holes in a rabbit model. The results of this study show that, in this rabbit model, the soft tissue graft maintained its biologic fixation in the osseous tunnel when stressed to failure at 1 year. The bony fixation occurred by the formation of an indirect tendon insertion, and this formation was complete by 26 weeks. At 52 weeks, large differences persisted in the strength and stiffness of the graft compared with the normal semitendinosus tendon and anterior cruciate ligament. Based on the results of this study, we support a cautious approach in returning patients to early full activity, including sports, after anterior cruciate ligament reconstruction with a semitendinosus autograft.