Comparison of 4 Femoral Tunnel Drilling Techniques in Anterior Cruciate Ligament Reconstruction

Purpose: The purpose of this study was to determine which femoral tunnel drilling technique most closely reproduces the anatomic femoral footprint and has acceptable tunnel length and tunnel orientation. Methods: We divided 20 cadaveric knees into 4 equal groups. Arthroscopically, the anatomic femoral footprint was marked with an awl as the tunnel starting point. In group 1 the femoral tunnel was drilled through a tibial tunnel. In groups 2 and 3 the femoral tunnel was drilled through the anteromedial arthroscopy portal, with a rigid drill and flexible drill, respectively. In group 4 the femoral tunnel was drilled with the outside-in technique over a pin positioned with an arthroscopic femoral guide. Measurements of the tunnel length, aperture, and placement were taken from 3-dimensional computed tomography scans. Results: Tunnel length for groups 1, 2, 3, and 4 averaged 42.08 mm, 37.73 mm, 28.92 mm, and 31.96 mm (P = .039). The mean coronal angle of the tunnels as measured from the line tangent to the posterior femoral condyles was 63.30 degrees, 61.22 degrees, 51.77 degrees, and 45.00 degrees (P = .007), and the mean distance from the inferior articular surface to the edge of the tunnel was 5.60 mm, 4.36 mm, 2.42 mm, and - 0.63 mm ( P = .008) for groups 1, 2, 3, and 4, respectively. There was no statistical difference in footprint length, width, area, or distance from the posterior articular margin. Conclusion: Drilling by the transtibial technique produces the most vertical and longest tunnels. Independent drilling techniques produce the most anatomic tunnels but at the expense of tunnel length. Clinical Relevance: When the orthopaedic surgeon is performing ACL reconstruction, it is critical to achieve anatomic placement of the graft, as well as maintain appropriate tunnel length.