Posterior Fan-Like Extension of the Anterior Cruciate Ligament Femoral Insertion Increases Ligament Failure Strength

The purpose of this study was to examine the role of the posterior fan-like extension (PFLE) region of the anterior cruciate ligament (ACL) on ligament failure load. It was hypothesized that transection of the PFLE region would reduce the ACL load-carrying capacity. With institutional approval, fifteen fresh frozen human cadaveric knees were divided into two age-matched groups: intact ACL femoral insertion (ACL intact group, n=8) and the cut ACL fan-like extension (PFLE Cut) group, n=7). In the PFLE Cut group, the border between the mid-substance insertion and the PFLE was identified at 90° of knee flexion, and the border was cut. All specimens were dissected down to the ACL and placed in an axial testing machine at 15° of flexion and anterior tibial loading was applied until ACL failure. The failure (peak) load of the ACL intact group was 910.1 ± 473.3 N, which was significantly greater (p < .05) than the failure load of the PFLE Cut group (409.5 ± 219.7 N). The displacement at the failure load of the ACL intact group was 21.7 ± 5.5 mm, which was significantly greater (p < .05) than the 14.5 ± 4.9 mm failure load displacement of the PFLE Cut group. Transection of the PFLE region of the ACL femoral footprint significantly reduced the failure load of the ligament under anterior tibial loading at 15° of flexion. The morphology of the ACL at the femoral insertion significantly affects the failure strength of the ligament. If ACL reconstruction grafts could be constructed to more closely mimic this geometry, they could potentially have increased failure strengths and reduce failure rates. Not applicable.