The anatomical features of ACL insertion sites and their implications for multi-bundle reconstruction

Abstract

The anatomical features of insertion sites of the anterior cruciate ligament (ACL) were reviewed and illustrated. The ACL generally had been divided into two bundles, i.e., the anteromedial (AM) and posterolateral (PL) bundle. However, subsequent studies suggested that the ACL could be separated into three bundles; the AM bundle was subdivided into the anteromedial bundle lateral part (AM-L bundle) and the anteromedial bundle medial part (AM-M bundle). The ACL insertion sites were easily discernable by distribution of the calcified fibrocartilage having smooth surface. In the femoral insertion, the AM-L bundle occupies the proximo-anterior part, and the AM-M bundle occupies the proximo-posterior part. The PL bundle occupies the distal part. In the tibial insertion, the AM-M bundle occupies the anteromedial part, and the AM-L bundle occupies the anterolateral part. The PL bundle occupies the posterior part. These positional relations of the insertion sites produce the differences of each bundle function and provide a rationale for performing multi-bundle ACL reconstruction.