Biomechanical Analysis of an Anatomic Anterior Cruciate Ligament Reconstruction

Abstract

Background: The focus of most anterior cruciate ligament reconstructions has been on replacing the anteromedial bundle and not the posterolateral bundle. Hypothesis: Anatomic two-bundle reconstruction restores knee kinematics more closely to normal than does single-bundle reconstruction. Study Design: Controlled laboratory study. Methods: Ten cadaveric knees were subjected to external loading conditions: 1) a 134-N anterior tibial load and 2) a combined rotatory load of 5-N·m internal tibial torque and 10-N·m valgus torque. Resulting knee kinematics and in situ force in the anterior cruciate ligament or replacement graft were determined by using a robotic/universal force-moment sensor testing system for 1) intact, 2) anterior cruciate ligament deficient, 3) single-bundle reconstructed, and 4) anatomically reconstructed knees. Results: Anterior tibial translation for the anatomic reconstruction was significantly closer to that of the intact knee than was the single-bundle reconstruction. The in situ force normalized to the intact anterior cruciate ligament for the anatomic reconstruction was 97% ± 9%, whereas the single-bundle reconstruction was only 89% ± 13%. With a combined rotatory load, the normalized in situ force for the single-bundle and anatomic reconstructions at 30° of flexion was 66% ± 40% and 91% ± 35%, respectively. Conclusions: Anatomic reconstruction may produce a better biomechanical outcome, especially during rotatory loads. Clinical Relevance: Results may lead to the use of a two-bundle technique.