Comparison of anterior cruciate ligament volume after anatomic double-bundle anterior cruciate ligament reconstruction

Backgroud To determine whether anatomic double-bundle anterior cruciate ligament reconstruction (DB-ACLR) can restore the native ACL volume, and whether the volume change after reconstruction affects clinical outcomes and re-rupture rates following the contemporary techniques. Methods Eighty patients undergoing anatomic DB-ACLR using transportal or outside-in technique were prospectively evaluated with magnetic resonance imaging (MRI) before and after surgery. The ACL volumes were determined from 3-D models constructed by applying reverse engineering software. In all participants, measured reconstructed ACL volume were compared with the ACL on the opposite uninjured side. Participants were divided into two groups according to the volume of reconstructed graft; larger volume than native ACL of contra-lateral side (Group 1) or smaller (Group 2). Results The mean ACL volume on the reconstructed side (1726.5 mm³, 982.1 - 2733.8) was significantly smaller than that on the uninjured opposite side (1857.6 mm³, 958.2 - 2871.5) (P < 0.001). A total of 31 patients in Group 1 and 49 in Group 2 showed no significant difference of improvement in the clinical outcome scales at the postoperative two-year follow-up (Lysholm knee score, P = 0.830, Tegner activity score, P = 0.848). Four patients with ACL re-rupture during the two-year follow-up after reconstruction had smaller reconstructed ACL volumes than native ligament on the opposite site. Conclusion Anatomic DB-ACLR technique restored the graft volume rather smaller than the volume of the native ACL. Based on the volumetric consideration, graft reconstructed by anatomic DB-ACLR might have increased probability of re-rupture due to its smaller volume related to native ACL on the contralateral side.