The femoral posterior fan-like extension of the ACL insertion increases the failure load

Purpose To examine the role of the posterior fan-like extension of the ACL’s femoral footprint on the ACL failure load. Methods Sixteen ( n = 16) fresh frozen, mature porcine knees were used in this study and randomized into two groups ( n = 8): intact femoral ACL insertion (ACL intact group) and cut posterior fan-like extension of the ACL (ACL cut group). In the ACL cut group, flexing the knees to 90°, created a folded border between the posterior fan-like extension and the midsubstance insertion of the femoral ACL footprint and the posterior fan-like extension was dissected and both areas were measured. Specimens were placed in a testing machine at 30° of flexion and subjected to anterior tibial loading (60 mm/min) until ACL failure. Results The intact ACL group had a femoral insertion area of 182.1 ± 17.1 mm 2 . In the ACL cut group, the midsubstance insertion area was 113.3 ± 16.6 mm 2 , and the cut posterior fan-like extension portion area was 67.1 ± 8.3 mm 2 . The failure load of the ACL intact group was 3599 ± 457 N and was significantly higher ( p < 0.001) than the failure load of the ACL cut group 392 ± 83 N. Conclusion Transection of the posterior fan-like extension of the ACL femoral footprint has a significant effect on the failure load of the ligament during anterior loading at full extension. Regarding clinical relevance, this study suggests the importance of the posterior fan-like extension of the ACL footprint which potentially may be retained with remnant preservation during ACL reconstruction. Femoral insertion remnant preservation may allow incorporation of the fan-like structure into the graft increasing graft strength.