Three-Dimensional Characterization of the Anterior Cruciate Ligament's Femoral Footprint

Abstract

There is increasing use of three-dimensional (3D) computed tomography (CT) for researching anterior cruciate ligament (ACL) reconstructions and tunnel placement. However, there is limited 3D CT data on the ACL footprint. The purpose of this study is to define the native ACL femoral footprint using 3D surface reconstructions of computed tomography (CT) imaging of cadaveric knees. The femoral insertion of the ACL was meticulously dissected and marked with drill holes in seven cadaveric knees. CT scans were performed on each specimen, and 3D computer models were created. Distance from the condyle edges to the margins of the footprint were referenced to the total condylar size. This was performed both parallel and perpendicular to the femoral axis as well as the intercondylar notch. The mean condylar depth (c/C) ratios along the axis of the femur were 0.45 ± 0.06 for the anterior border, 0.44 ± 0.08 for the posterior border, 0.26 ± 0.07 for the proximal border, and 0.63 ± 0.08 for the distal border. The mean notch (n/N) ratios for the four margins were 0.37 ± 0.04 for the anterior border, 0.67 ± 0.08 for the posterior border, 0.49 ± 0.07 for the proximal margin, and 0.50 ± 0.06 for the distal border. The mean c/C ratios parallel the intercondylar notch measured 0.23 ± 0.03 for the anterior border, 0.27 ± 0.04 for the posterior border, 0.37 ± 0.04 for the proximal border, and 0.12 ± 0.02 for the distal border. The mean n/N ratios perpendicular to the intercondylar notch measured 0.11 ± 0.06 for the anterior border, 0.52 ± 0.09 the posterior border, 0.29 ± 0.06 for the proximal border, and 0.30 ± 0.06 for the distal border. This study provides reference measures of the femoral footprint of the ACL using 3D CT. It will assist future studies that use advanced imaging to evaluate accuracy of ACL reconstruction.

Radiologic assessment of femoral and tibial tunnel placement based on anatomic landmarks in arthroscopic single bundle anterior cruciate ligament reconstruction

“…In the patients who were felt to have technical problems contributing to their failure, 80% believed to have femoral tunnel malposition. Various studies have described arthroscopic and anatomic landmarks for successful placement of tibial and femoral tunnels for ACLR 56. We placed femoral tunnel slightly posterior to the center of the native footprint so that the tunnel will have 3 mm of intact posterior wall and about 3 mm superior to the articular cartilage.…”

The effect of feedback from post-operative 3D CT on placement of femoral tunnels in single-bundle anatomic ACL reconstruction

“…The empirical anatomical centre, used as a reference for the tunnel localization in the present study, represents a summation of findings from a range of cadaveric studies [6]. To date, this represents the most comprehensive measure for the centre of the femoral footprint that can be projected onto the B&H grid for use as a representation of an ideal position of the femoral graft tunnel when performing a single-bundle anatomic reconstruction and evaluating by post-operative 3D CT. A recent publication from Westermann et al [36] described the femoral insertion of the ACL in seven cadaveric knees, marking the outline and performing CT scans to obtain an average CT reference for tunnel placement. In a 2D coordinate system, similar to the B&H grid, a quadrant representing the location of the femoral ACL insertion was then suggested by the mean borders of the ACL in the two axes of the coordinate system.…”