Anatomic Femoral Tunnel Drilling in Anterior Cruciate Ligament Reconstruction Use of an Accessory Medial Portal Versus Traditional Transtibial Drilling

Background: During anatomic anterior cruciate ligament (ACL) reconstruction, we have found that the femoral footprint can best be visualized from the anteromedial portal. Independent femoral tunnel drilling can then be performed through an accessory medial portal, medial and inferior to the standard anteromedial portal. Purpose: To compare the accuracy of independent femoral tunnel placement relative to the ACL footprint using an accessory medial portal versus tunnel placement with a traditional transtibial technique. Study Design: Controlled laboratory study. Methods: Ten matched pairs of cadaveric knees were randomized such that within each pair, one knee underwent arthroscopic transtibial (TT) drilling, and the other underwent drilling through an accessory medial portal (AM). All knees underwent computed tomography (CT) both preoperatively and postoperatively with a technique optimized for ligament evaluation (80 keV with maximum mAs). Computed tomography was performed with a dual-energy scanner. Commercially available third-party software was used to fuse the preoperative and postoperative CT scans, allowing anatomic comparison of the ACL footprint to the drilled tunnel. The ACL footprint was marked in consensus by an orthopaedic surgeon and a musculoskeletal radiologist and then compared with the tunnel aperture after drilling. The percentage of tunnel aperture contained within the native footprint as well as the distance from the center of the tunnel aperture to the center of the footprint was measured. Results: The AM technique placed 97.7% +/- 5% of the tunnel within the native femoral footprint, significantly more than 61.2% +/- 24% for the TT technique (P = .001). The AM technique placed the center of the femoral tunnel 3.6 +/- 1.2 mm from the center of the native footprint, significantly closer than 6.0 +/- 1.9 mm for the TT technique (P = .003). Conclusion: This study demonstrates that use of an accessory medial portal will facilitate more accurate placement of the femoral tunnel in the native ACL femoral footprint. Clinical Relevance: More accurate placement of the femoral tunnel in the native ACL femoral footprint should improve the ability to achieve more anatomic positioning of the ACL graft.