Magnetic resonance imaging at different time periods following hamstring harvest for anterior cruciate ligament reconstruction

Purpose: The purpose of this study was to evaluate the magnetic resonance i maging (MRI) appearance of the hamstring graft harvest site after harvestin g the hamstring tendons to reconstruct a torn anterior cruciate ligament (A CL). Type of Study: Case series. Methods: We performed MRI on 21 patients w ho had previously undergone hamstring harvest and ACL reconstruction. Twent y of the patients (7 female and 13 male; mean age, 37 years; range, 16 to 8 4 years), all volunteers, were selected from a series of 45 ACL reconstruct ions per formed by the senior author during a 20-month period. Another pati ent, a 32-year-old man, underwent ACL reconstruction elsewhere 32 months be fore. Both the semitendinosus and gracilis tendons were harvested in all ca ses. All MRIs were obtained on a 1.5-T magnet and were prospectively evalua ted by 2 experienced musculoskeletal radiologists who were blinded to the t ime interval between graft harvest and MRI. Results: Two weeks after graft harvest, MRI showed ill-defined intermediate signal on T1-weighted images a nd increased signal on T2-weighted images, consistent with fluid in the har vest site, with no discernable tendon. At 6 weeks, structures were seen at the level of the superior pole of the patella that had morphology and signa l characteristics similar to native tendon. By 3 months, structures with no rmal morphology and signal characteristics were seen to the level of the jo int line, and by 12 months, to the level of 1 to 3 cm above that of the tib ial attachment. At 32 months, the tendons appeared on MRI to normalize to a level of 1 to 2 cm above their tibial attachment. Conclusion: Following ha mstring tendon harvest, MRI demonstrates an apparent regeneration of tendon s beginning proximally and extending distally over time.