Comparative Kinematic Evaluation of All-Inside Single-Bundle and Double-Bundle Anterior Cruciate Ligament Reconstruction A Biomechanical Study

Background: The efficacy of single-bundle versus double-bundle ACL reconstruction in improving knee stability has been widely discussed. The biomechanics of all-inside double-bundle ACL reconstructions have not been evaluated. Hypothesis: An anatomic all-inside double-bundle ACL reconstruction will more effectively restore native knee kinematics in vitro, especially rotational stability, when compared with an all-inside single-bundle ACL reconstruction. Study Design: Controlled laboratory study. Methods: Seven pairs of fresh-frozen cadaveric human knees were used. Knees were tested using 88 N of force for anterior and posterior drawers, 5 N.m internal and external rotation moments, 10 N.m valgus and varus moments, and coupled 5 N.m internal rotation and 10 N.m valgus moments to simulate a pivot shift at 0 degrees, 20 degrees, 30 degrees, 60 degrees, and 90 degrees of knee flexion. Motion of the knee in response to external loading was measured with a Polhemus electromagnetic tracking system. Knees were first tested in the intact state, with either the anteromedial or posterolateral bundle cut, and then with both bundles cut. Subsequently, 7 single-bundle and 7 double-bundle all-inside ACL reconstructions were performed. Results: Both single-and double-bundle all-inside ACL reconstructions restored knee kinematics for posterior drawer, varus/valgus rotation, and internal/external rotation motions. After single-bundle all-inside ACL reconstruction, anterior translation during the simulated pivot-shift test was significantly higher compared with the intact state at 20 degrees, 30 degrees, and 60 degrees of flexion. There was no significant difference between the double-bundle all-inside ACL reconstruction and the intact knee during a simulated pivot shift. Conclusion: We found that an all-inside double-bundle ACL reconstruction demonstrated significant improvement in restoring normal rotational knee motion during simulated pivot-shift testing compared with single-bundle ACL reconstructions in vitro, with no significant differences in other knee loading conditions. Clinical Relevance: All-inside double-bundle ACL reconstruction may provide advantages over single-bundle ACL reconstruction for rotational knee stability.