The forgotten third: understanding the ACL femoral insertion and lateral intercondylar ridge extension onto the notch roof.

PURPOSE

This study assesses the positioning of the lateral intercondylar ridge (LIR) and the anterior cruciate ligament (ACL) femoral insertion area (FIA) in relation to the femoral notch roof and the lateral notch wall and examines its correlation with the width of the posterior notch outlet.

METHOD

45 dried femurs underwent 3D scanning. A cutting plane was established to divide the intercondylar roof from the condylar wall based on three points. The length of the LIR on the roof and wall were measured, along with the distances from key landmarks. The total ACL-FIA and the areas on the roof and wall of the intercondylar notch were measured.

RESULTS

A significant correlation was found between the LIR position on the roof and the width of the notch. LIR averaged 16.18 mm, with 30.86% on the roof, while ACL-FIA averaged 134.19 mm², with 31.55% on the roof. The width of the posterior notch outlet was averaged at 24.34 mm. The distance between the most proximal part of the LIR and the posterior intercondylar line averaged 4.87 mm and 12.46 mm to the most proximal and deepest point of the cartilage border of the lateral femoral condyle.

CONCLUSION

This study confirms that approximately 30% of the LIR and ACL-FIA extend to the intercondylar notch roof, with a significant moderate positive correlation with the width of the posterior notch outlet. These findings highlight the need to consider the notch roof in the placement of the femoral tunnel for improved anatomical reconstruction of the ACL.