MRI of the Semitendinosus and Gracilis Tendons Minimum Six Years After Autograft Harvest for ACL Reconstruction

INTRODUCTION: The aim of the study was to investigate to what extent the semitendinosus and gracilis tendons had regenerated a minimum of six years after harvest for anterior cruciate ligament (ACL) reconstruction. The place of insertion and the area of the regenerated tendons were compared with the normal contra lateral side. To evaluate the function of the regenerated tendons, the strength in knee flexion and internal rotation of the tibia were measured on both sides. METHODS: Twenty patients (nine female and 11 male) who had undergone ipsilateral ACL reconstruction a minimum six years earlier, median 8.5 (6-11), using semitendinosus and gracilis autografts underwent bilateral magnetic resonance imaging (MRI) of their knees. An experienced independent muscleoskeletal radiologist evaluated all MRI examinations. Strength measurements in deep knee flexion and internal rotation were performed. RESULTS: The semitendinosus tendon had regenerated in 18/20 (90%) and the gracilis tendon in 19/20 (95%) of the patients as seen on MRI. There were no significant differences between the insertion place of the tendons on the operated and non-operated side. The cross sectional areas of the regenerated tendons revealed no significant differences compared to the normal tendons on the contralateral side, as measured 4 cm above the joint line. The patients were significantly weaker in deep knee flexion at 60 and 180 deg/s but stronger in internal rotation of the tibia at 60 deg/s in the operated leg compared to the non-operated knee. DISCUSSION AND CONCLUSION: The semitendinosus and gracilis tendons regenerated in the majority of patients and regained a nearly normal insertion place on the pes anserinus minimum six years after harvest. The regenerated tendons had a cross-sectional area similar to the non-operated contralateral side. The patients revealed a strength deficit in deep knee flexion but not in internal rotation.