MRI analysis of the attachment of the anteromedial and posterolateral bundles of anterior cruciate ligament using coronal oblique images

Purpose The purpose of this study was to evaluate the course of the anteromedial bundle (AMB) and the posterolateral bundle (PLB) of the anterior cruciate ligament (ACL) with magnetic resonance imaging (MRI) in order to clarify the relationship between the bundles and surrounding anatomic landmarks. Methods Eighty-eight knees with intact ACLs were included in this study. MRI coronal oblique images were obtained with the knee in extension and used to assess the following characteristics of the AMB and PLB: (1) course of the ligament, (2) location of the tibial attachment, and (3) femoral attachment and geometry of the lateral femoral condyle inner wall. Results In terms of the tibial attachment, the AMB was confluent with the apex of the medial intercondylar ridge (MIR) in all cases. Sixty-five PLBs (74%) inserted into the region between the apex and the slope of the MIR. The resident's ridge was detected in 91% of the knees in the AMB image, whereas the ridge was clearly visualized in only 17% of the knees in the PLB image. A bony eminence was observed at the inner articular margin of the lateral femoral condyle in the PLB image. Conclusion In terms of the tibial attachment, the AMB was confluent with the apex of the medial intercondylar ridge in all cases. Most of the PLBs attached to the region between the apex and the slope of the MIR. Because the bone tunnel location influences clearance between the grafts and the surrounding tissues, these results should be considered during anatomic double-bundle ACL reconstruction.