Magnetic Resonance Imaging at Different Time Periods Following Hamstring Harvest for Anterior Cruciate Ligament Reconstruction Damian M. Rispoli, M.D., Maj USAF, MC, Timothy G. Sanders, M.D., Lt Col USAF, MC, Mark D. Miller, M.D., Lt Col USAF, MC, and William B. Morrison, M.D. Purpose: The purpose of this study was to evaluate the magnetic resonance imaging (MRI) appearance of the hamstring graft harvest site after harvesting the hamstring tendons to reconstruct a torn anterior cruciate ligament (ACL). Type of Study: Case series. Methods: We performed MRI on 21 patients who had previously undergone hamstring harvest and ACL reconstruction. Twenty of the patients (7 female and 13 male; mean age, 37 years; range, 16 to 84 years), all volunteers, were selected from a series of 45 ACL reconstructions performed by the senior author during a 20-month period. Another patient, a 32-year-old man, underwent ACL reconstruction elsewhere 32 months before. Both the semitendinosus and gracilis tendons were harvested in all cases. All MRIs were obtained on a 1.5-T magnet and were prospectively evaluated by 2 experienced musculoskeletal radiologists who were blinded to the time interval between graft harvest and MRI. Results: Two weeks after graft harvest, MRI showed ill-defined intermediate signal on T1-weighted images and increased signal on T2-weighted images, consistent with fluid in the harvest 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 signal characteristics similar to native tendon. By 3 months, structures with normal morphology and signal characteristics were seen to the level of the joint line, and by 12 months, to the level of 1 to 3 cm above that of the tibial 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 hamstring tendon harvest, MRI demonstrates an apparent regeneration of tendons beginning proximally and extending distally over time. Key Words: Anterior cruciate ligament—Surgery—Magnetic reso- nance imaging—Hamstring tendons. H amstring tendon grafts have been used increas- ingly to reconstruct torn anterior cruciate liga- ment (ACL). 1 The hamstring graft is especially useful in older patients with patellofemoral arthrosis, patients with patellofemoral arthralgia or a history of anterior knee pain, and in revision surgery following patellar tendon harvest. 2,3 Regrowth of patellar tendon graft defects has been well described 4,5 and, although reharvesting of this tendon has been proposed, 6,7 patellar tendon grafts taken from a previous harvest site have been shown to be both biomechanically 4 and clinically inferior. 6 Hamstring grafts have been shown to regenerate to the level of the medial head of the gastrocnemius both clinically and, in a few patients, on magnetic reso- nance imaging (MRI). 8,9 Hamstring strength has been reported to return to almost normal values within 3 months of ACL reconstruction using semitendinosus and gracilis graft in 1 recent study. 10 MRI evaluation From the Department of Orthopaedics, Wilford Hall Medical Center, San Antonio, Texas (D.M.R., M.D.M.); the Departments of Radiology, The University of Texas, Health Science Center at San Antonio and Wilford Hall Medical Center (T.G.S.); and the De- partment of Radiology, Thomas Jefferson University Hospital, Philadelphia, Pennsylvania (W.B.M.), U.S.A. Address correspondence and reprint requests to Timothy G. Sanders, M.D., Lt Col USAF, MC, Department of Radiology, Wilford Hall Medical Center, 759th MDTS/MTRD, 2200 Bergquist Dr, STE 1, Lackland AFB, TX 78236-5300, U.S.A. E-mail: RADMANGS@cs.com This is a US government work. There are no restrictions on its use. 0749-8063/01/1701-2454$0.00/0 doi:10.1053/jars.2001.19460 2 Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 17, No 1 (January), 2001: pp 2– 8