Cadaveric knee observation study for describing anatomic femoral tunnel placement for two-bundle anterior cruciate ligament reconstruction

Purpose: The recently developed 2-bundle anterior cruciate ligament (ACL) reconstruction lacks sufficient anatomic background. The purpose of this anatomic study was to describe functional anteromedial (AM) and posterolateral (PL) portions of the natural ACL and to provide a reproducible description of the graft placement. Our hypothesis was that the core functional area of the femoral ACL attachment will be revealed by removing the surface fibrous membranous tissue of the ACL midsubstance and the attachment area. Methods: The natural ACL was divided into 2 portions of AM and PL bundles in a flexion position; those bundles were most clearly defined when the knee was in flexion. The surface membrane of the ACL was removed and the margin was marked. The attachment site was removed after documenting its measurements. The knee position was corrected by digital photographs with the femoral bone in the correct lateral position. Results: The length of the major axis of the AM and PL bundles averaged 9.2 +/- 0.7 mm and 6.0 +/- 0.8 mm, respectively. Both lengths of the minor axis of AM and PL bundles averaged 4.7 +/- 0.6 mm. The distance from the attachment center of each AM and PL bundle to the posterior bone and articular surface border averaged 6.3 +/- 0.6 mm and 8.6 +/- 0.6 mm, respectively. The center of the AM and PL bundles was described as 1:40 and 3: 10 clock positions, respectively, as left knee when the point was defined on the "lateral wall clock" of the intercondylar notch. Conclusions: The study described the position and area of each 2-bundle of AM and PL portions of the natural ACL by describing its central structure with the surface membrane removed. Clinical Relevance: The detailed anatomic description of the natural ACL femoral attachment might suggest to surgeons where to make femoral tunnels during 2-bundle reconstruction.