Arbitrary Starting Point of Separation Affects Morphology of the 2 Bundles of Anterior Cruciate Ligament at Insertion Sites

Purpose

To explore whether changes in the starting point of separation affect the morphology of the 2 bundles of the anterior cruciate ligament (ACL) at insertion.

Methods

Ten cadaveric knees were used to separate the ACL fibers into 2 bundles from 3 different starting points that were located at the proximal one fifth, two fifths, and three fifths of the inter-bundle mark line. The dividing lines between the 2 bundles at insertion and the area of the anteromedial (AM) bundle resulting from these different separations were compared, with data collected in groups I, II, and III, respectively.

Results

The angle of the dividing line and the long axis of the femoral footprint was 67.24° ± 11.94°, 91.01° ± 11.16°, and 116.03° ± 9.01° in groups I, II, and III, respectively, and the percentage of the AM bundle area in the whole femoral footprint was 38.64% ± 5.55%, 52.22% ± 6.76%, and 65.09% ± 4.53%, respectively. At the tibial insertion sites, the angle between the dividing line and the sagittal plane was 110.17° ± 13.26°, 127.72° ± 8.94°, and 149.28° ± 18.80° in groups I, II, and III, respectively, and the percentage of the AM bundle area in the whole footprint was 25.72% ± 3.82%, 40.41% ± 3.73%, and 60.56% ± 6.59%, respectively. There were statistical differences between the angle and the area data of each of the 2 groups at either the tibial or femoral insertion site.

Conclusions

In an anatomic study of the ACL, changes in the point from which separation started resulted in noticeably different bundle morphology at the insertion.

Clinical Relevance

Proper separation will lead to a more accurate bundle description and, thus, a more accurate location of the tunnels in ACL reconstruction.