Anatomic Single-Graft Anterior Cruciate Ligament Reconstruction Restores Rotational Stability: A Robotic Study in Cadaveric Knees

Purpose: First, we aimed to investigate the ability of a single bone-patellar tendon-bone graft placed in the anatomic center of the femoral and tibial attachment sites to restore normal tibiofemoral compartment translations and tibial rotation. Second, we aimed to investigate what combination of anterior load and internal rotation torque applied during a pivot-shift test produces maximal anterior tibiofemoral subluxations. Methods: We used a 6-df robotic simulator to test 10 fresh-frozen cadaveric specimens under anterior cruciate ligament (ACL) eintact, ACL-sectioned, and ACL-reconstructed conditions measuring anterior translations of the medial, central, and lateral tibiofemoral compartments and degrees of tibial rotation. Specimens were loaded under Lachman, anterior limit, and internal rotation conditions, as well as 3 different pivot-shift conditions. Results: On ACL sectioning, compartment translations in the Lachman and 3 pivot-shift tests increased significantly and were restored to ACL-intact values after single-graft ACL reconstruction. In the pivot-shift tests, the single graft restored lateral and medial compartment translations (e.g., group 3, within 1.3 +/- 0.6 mm and 0.8 +/- 0.6 mm, respectively, of the ACL-intact state and internal rotation within 0.7 degrees +/- 1.2 degrees). Anterior subluxation of the medial compartment during pivot-shift loading was reduced when internal rotation torque was increased from 1 to 5 Nm (P < .0001). Conclusions: A single-graft ACL reconstruction performed at the central femoral and tibial ACL attachment sites restored anterior-posterior translation and tibial rotation motion limits. In addition, rotational knee stability as defined by tibiofemoral compartment translations was restored under all simulated pivot-shift testing conditions.