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

Abstract

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 mm2. In the ACL cut group, the midsubstance insertion area was 113.3 ± 16.6 mm2, and the cut posterior fan‐like extension portion area was 67.1 ± 8.3 mm2. 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.

Failure load of the femoral insertion site of the anterior cruciate ligament in a porcine model: comparison of different portions and knee flexion angles

“…This study showed no significant differences in failure loads between the anterior portion (direct insertion) and the posterior portion of the ACL femoral insertion site (mainly consisting of indirect insertion) in 30 degrees of flexion. This result agrees with that of a previous biomechanical study on the femoral posterior fan-like extension of the ACL [13]. This implies that the indirect insertion of the ACL [7], the so-called fan-like extension fibers [8], significantly contributes to ACL strength.…”

“…In addition, our histological study showed that the porcine ACL femoral insertion site consisted of direct and indirect insertions in the anterior and posterior portions, respectively; this histological structure is also similar to that of humans [6,7]. Therefore, the porcine knee is considered to be the preferred model for experimental biomechanical studies [25], since it can be matched by size and age [13]. Human cadaver knees are difficult to obtain at younger ages, at which ACL injuries occur.…”

“…Recently, Sabzevari et al [13] demonstrated the importance of the posterior fan-like extension of the femoral ACL insertion site in increasing the ligament failure load. However, the significance of tunnel placement at this location is clinically unclear.…”

A Modified Anatomic Transtibial Double-Bundle Anterior Cruciate Ligament Reconstruction Provides Reliable Bone Tunnel Positioning

“…Incidental histologic studies proved that the femoral ACL insertion area had spread more distally and posteriorly into the region called the area of indirect insertion or fun-like extension fibers. 30 , 31 , 32 The fan-like extension fibers significantly functioned with increasing ACL failure load. 30 According to the modified definitive area of ACL fiber attachment, the accuracy of our modified double-bundle transtibial tunnel creation technique was estimated at 92.6% of the anatomic tunnel creation.…”

“… 30 , 31 , 32 The fan-like extension fibers significantly functioned with increasing ACL failure load. 30 According to the modified definitive area of ACL fiber attachment, the accuracy of our modified double-bundle transtibial tunnel creation technique was estimated at 92.6% of the anatomic tunnel creation.…”