Anterior Cruciate Ligament Reconstruction Femoral Tunnel Characteristics Using an Accessory Medial Portal Versus Traditional Transtibial Drilling

PurposeTo evaluate anterior cruciate ligament femoral tunnel characteristics using an accessory medial (AM) portal and transtibial (TT) drilling.MethodsTen matched pairs of cadaveric knees underwent arthroscopic AM portal or TT femoral drilling with 8-mm reamers. All knees underwent computed tomography scanning and were evaluated for tunnel aperture area, shape as described by the length of the long and short axes, location of the tunnel relative to the anterior and inferior aspects of the articular surface with the knee in extension, tunnel angle in the coronal and axial planes, and tunnel length.ResultsThe femoral tunnel aperture area was 50.5 ± 4.8 mm2 for AM portal drilling and 51.9 ± 4.6 mm2 for TT drilling (P = .5). The femoral tunnel aperture long axis was 8.5 ± 1.1 mm for AM portal drilling and 9.2 ± 1.3 mm for TT drilling (P = .2), and the short axis was 8.0 ± 0.5 mm for AM portal drilling and 8.0 ± 0.5 mm for TT drilling (P = .8). The femoral tunnel aperture was 5.0 ± 1.4 mm from the anterior wall for AM portal drilling and 9.9 ± 1.7 mm for TT drilling (P < .001), and it was 7.6 ± 2.4 mm from the inferior articular surface for AM portal drilling and 8.9 ± 2.2 mm for TT drilling (P = .2). The femoral tunnel orientation in the coronal plane was 42.1° ± 4.8° for AM portal drilling and 60.9° ± 6.7° for TT drilling (P < .001), and the orientation in the axial plane was 20.9° ± 4.4° for AM portal drilling and 22.7° ± 13.5° for TT drilling (P = .7). The femoral tunnel length was 35.6 ± 2.8 mm for AM portal drilling and 40.3 ± 7.9 mm for TT drilling (P = .1).ConclusionsThe use of an AM portal creates a tunnel more anterior and more horizontal than tunnels created by a TT technique.Clinical RelevanceThe femoral tunnel characteristics may have an effect on the strain placed on the graft, the graft bending angle, whether enough graft can be placed into the tunnel, and, ultimately, the ability of the body to fully heal the graft.