An Anatomical and Biomechanical Comparison of Anteromedial and Anterolateral Approaches for Tibial Tunnel of Posterior Cruciate Ligament Reconstruction: Evaluation of the Widening Effect of the Anterolateral Approach

Abstract

Background An anterolateral approach to the tibial tunnel of posterior cruciate ligament reconstruction is used to reduce the sharpness of the graft-tunnel angle, the so-called killer turn effect. However, with the anterolateral approach, the tunnel might be widened into an ovoid shape because of the small angle between the tunnel and the anterolateral cortex. Hypothesis The fixation strength of the posterior cruciate ligament graft in the tibial tunnel will be weaker in the anterolateral approach compared with the anteromedial approach. Study Design Controlled laboratory study. Methods Twenty paired cadaveric tibias were used. Tibial tunnels were made using following approaches: an anteromedial approach for 10 tibias and an anterolateral approach for 10 tibias. The anterior cortex-tunnel angle and the diameter of the tunnel entrance were measured by 2-dimensional computed tomographic scans. After fixation of the Achilles tendon allograft with a biodegradable screw, the maximal strength of the graft at failure was measured using a materials testing machine. Results The mean cortex-tunnel angle was 47.5° ± 9.3° in the anteromedial approach group and 28.3° ± 7.4° in the anterolateral approach group. The mean long diameter of the tunnels in the anteromedial approach group was 10.6 ± 1.0 mm and in the anterolateral approach group it was 14.0 ± 1.5 mm. These two parameters showed statistically significant differences between the 2 groups (P < .01). The mean maximum load at failure for the anteromedial approach group was 385.4 ± 139.7 N, and for the anterolateral approach group it was 225.1 ± 144.1 N. This difference was statistically significant (P = .021). Conclusion The anterolateral approach resulted in a tunnel with a wider entrance, a more acute cortex-tunnel angle, and a lower maximal load at failure compared with tunnels created using the anteromedial approach. Clinical Relevance The use of additional fixation methods, such as post ties or ligament washers and screws, should be considered when using an anterolateral approach for tibial tunnel of posterior cruciate ligament reconstruction.