Evaluation of hamstring strength and tendon regrowth after harvesting for anterior cruciate ligament reconstruction

Background: It is generally thought that tissue regeneration and good functional recovery can be expected after anterior cruciate ligament reconstruction using the hamstring tendons. However, persistent strength deficit in deep knee flexion has also been reported. Hypothesis: Morphologic regeneration of the harvested hamstring tendon is not necessarily associated with its functional recovery. Study Design: Retrospective follow-up study. Method: Twenty-eight patients who underwent anterior cruciate ligament reconstruction with hamstring graft were evaluated after a minimum period of 2 years. Status of tendon regrowth was assessed by magnetic resonance imaging. To specifically analyze the functional deficit after graft harvest, the isometric hamstring strength was examined in a sitting position at 90degrees of flexion and a prone position at 90degrees and 110degrees of flexion. Then, the strength data were correlated with the extent of tendon regeneration. Results: In 22 of the 28 patients, a regrowth of the semitendinosus tendon was found, whereas regeneration of the gracilis tendon was observed in 13 patients. In the evaluation of hamstring strength, the isometric peak torque was reduced to 86.2%, 54.6%, and 49.1%, respectively, in the aforementioned 3 postures as compared with the contralateral side. Conclusions: Significant functional deficit of hamstring strength remains regardless of morphologic regeneration.