Single-Bundle Anterior Cruciate Ligament Reconstruction A Comparison of Conventional, Central, and Horizontal Single-Bundle Virtual Graft Positions

Background: Conventional endoscopic single-bundle transtibial anterior cruciate ligament (ACL) reconstruction from the posterolateral tibial footprint to the anteromedial femoral footprint results in a vertical graft. A more oblique horizontal graft from the anteromedial tibial footprint to the posterolateral femoral footprint may offer a better alternative for all endoscopic ACL reconstruction. Hypothesis: When compared with a conventional ACL single-bundle position, the horizontal graft ACL position has more obliquity and so undergoes a greater change in length during anterior translation and internal rotation. Study Design: Controlled laboratory study. Methods: A computer navigation system was used to acquire kinematic data during a flexion-extension cycle and outline the anteromedial and posterolateral aspects of the tibial and femoral footprints on 5 fresh-frozen cadaveric knees. Three virtual graft positions were defined: conventional (posterolateral tibia-anteromedial femur), central, and horizontal (anteromedial tibia posterolateral femur). After transection of the ACL, the obliquity, anisometry, absolute length change, and apparent strain were computed for each graft position during the Lachman test, the anterior drawer test, and internal rotation at 0 and 30 of flexion. Results: The horizontal position was more oblique than the other positions (P < .05). There were no differences in anisometry. The horizontal position elongated more than the other positions during the Lachman test (P < .05) and more than the conventional position during the anterior drawer test (P = .009). During internal rotation at 30 flexion, the horizontal position elongated more than the other positions (P < .05). The central and horizontal positions had more apparent strain than that of the vertical position during the Lachman test and internal rotation (P < .05); no significant difference was found during the anterior drawer test. Conclusion: In ACL-deficient cadaveric knees, the horizontal graft position has greater obliquity and so undergoes greater elongation without increased apparent strain when compared to the central graft position, in response to anterior translation and internal rotation maneuvers.