Serial Evaluation of Human Anterior Cruciate Ligament Grafts by Contrast-Enhanced Magnetic Resonance Imaging: Comparison of Allografts and Autografts

Abstract

The purpose of this study was to clarify the difference in remodeling between allografts and autografts in anterior cruciate ligament reconstruction. We examined 24 knees with bone-patellar tendon-bone allografts and 20 knees with central-third bone-patellar tendon-bone autografts. Surgical patients from January 1997 to December 2002 were included in the study, and more than 1 year had passed since surgery. The mean postoperative follow-up was 24.0 months in the allograft group and 21.3 months in the autograft group. Patients with a positive Lachman test were excluded. The operative method and postoperative rehabilitation programs were the same. All allografts were provided by Tokai Regional Bone Bank, the only regional bone bank in Japan. Contrast-enhanced magnetic resonance imaging (1.0 T, T1-weighted, sagittal section, infusion of 0.2-mL/kg gadolinium-diethylenetriamine pentaacetic acid [Gd-DTPA]) was performed for all knees at 1, 4, 6, and 12 months after surgery and performed for some knees irregularly thereafter. The signal/noise quotient (SNQ) of grafts was calculated by use of magnetic resonance imaging based on the method of Weiler et al. (2001) as follows: SNQ = (Signal of ACL graft - Signal of quadriceps tendon)/Signal of background. The SNQ of allografts was significantly lower than for autografts 12 months after surgery. As for the SNQ 1 month after surgery, there was no difference before or after Gd-DTPA infusion in the allografts; however, the SNQ was significantly higher after Gd-DTPA infusion in autografts. The SNQ after Gd-DTPA infusion continued to increase until 12 to 24 months in the allograft group but peaked at 4 or 6 months in the autograft group. Compared with autologous tendons, allogeneic tendons have a slower onset and rate of revascularization. Level III, retrospective comparative study.