Knee Flexor Strength and Donor Site Regeneration after Harvesting Semitendinosus Tendon for Anterior Cruciate Ligament Reconstruction

The tendon-like tissue regeneration at the portion of harvested semitendinosus tendon (ST) is observed in some knees underwent ACL reconstruction using hamstring tendons. The purpose of this study is to investigate the effect of regenerated tissue on the postoperative knee flexor strength. 20 consecutive patients whose injured ACL were reconstructed using hamstring tendons were divided into two subgroups, depending on the regeneration of the tendon relief and MRI findings at a follow-up time of more than 2 years. The regeneration group consisted of 14 patients with apparent tendon-like tissue in the ST harvested portion, while the non-regeneration group consisted of the remaining 6 patients without any such tissue. All patients were evaluated by the isokinetic maximum torque of the knee flexor strength using Cybex II and the flexion lag. The maximum torques of the regeneration and non-regeneration groups were 93.4±10.2% and 93.2±11.2%, respectively, showing no significant differences. Conversely, the flexion lag in the regeneration group was 3.2±2.0 degrees, while significantly lower than 8.0±2.2 degrees in the non-regeneration one. Our results suggest the possibility that the regenerated tendon-like tissue might act as well as normal ST.