Osseous landmarks of the femoral attachment of the anterior cruciate ligament: an anatomic study.

Purpose: Anatomic tunnel placement is critical to the success of anterior cruciate ligament (ACL) reconstruction. The purpose of this study was to determine qualitatively and quantitatively the osseous landmarks of femoral attachment of the ACL.

Methods: The femoral attachment of the ACL was studied histologically in seven human fetuses, arthroscopically in 60 patients who underwent ACL surgery, and grossly in 16 cadaveric knees. Three-dimensional laser digitizer pictures of the cadaveric specimens were taken to quantify length, area, and angulations of the femoral attachment of the ACL.

Results: Two different osseous landmarks were detected. An osseous ridge that runs from proximal to distal ends was present in all the arthroscopic patients and cadaveric knees. It was named "lateral intercondylar ridge." Another osseous landmark between the femoral attachment of the anteromedial (AM) and posterolateral (PL) bundles running from anterior to posterior was observed in 6 out of 7 fetuses, 49 out of 60 arthroscopic patients, and 13 out of 16 cadaveric knees. It was named "lateral bifurcate ridge." A change of slope between the femoral attachment of the AM and PL bundles was observed in all specimens studied. The femoral attachment of the AM bundle formed an angle with the PL bundle of 27.6 degrees +/- 8.8 degrees and a radius of curvature of 25.7 +/- 12 mm. The area of the entire ACL footprint, AM, and PL bundle was 196.8 +/- 23.1 mm(2), 120 +/- 19 mm(2), and 76.8 +/- 15 mm(2), respectively.

Conclusions: The ACL femoral attachment has a unique topography with a constant presence of the lateral intercondylar ridge and often an osseous ridge between AM and PL femoral attachment, the lateral bifurcate ridge.

Clinical Relevance: These findings may assist surgeons to perform ACL surgery in a more anatomic fashion.