The slope of anterior cruciate ligament bundles for accurate transtibial anatomic reconstruction: a cadaveric study

Abstract

Objectives Several studies have shown that femoral tunnel placement during double bundle anterior cruciate ligament reconstruction through the anteromedial (AM) portal is more accurate compared with the transtibial technique. Our hypothesis is that, for proper transtibial placement of the femoral tunnels, not only the anatomical sites of the tibial tunnels are important but also the slope of the tibial tunnels should match the native slope of the corresponding bundle. The anatomic insertions of the anterior cruciate ligament bundles in the femur and the tibia are well reported in the literature, but to our knowledge no study has reported the degrees of slope of the bundles. Materials and methods We examined eight cadaveric knees of middle-aged adults. The angle between each bundle and the tibial plateau was measured in both planes. The sagittal plane was measured between the bundle and the posterior tibial plateau with the knee flexed at 90°. The coronal plane was measured between the bundle and the lateral tibial plateau with the knee flexed at 90°. Results In the sagittal plane, the mean slope angle was 55.5° for the AM bundles and 90.6° for the posterolateral (PL) bundles. In the coronal plane, the mean slope angle was 80.6° for the AM and 81.3° for the PL bundles. Conclusion Focusing on the slope angles of the PL bundle in the sagittal plane (90.6°), we found that this bundle is oriented almost perpendicular to the tibial plateau. This means that for proper transtibial drilling the starting point should be from the posteromedial surface of the tibia behind the medial collateral ligament. Clinical relevance We confirm that transtibial drilling of the PL bundle is not applicable with the classic starting points on the AM surface of the tibia, and thus transportal techniques are better.