Stiffer Fixation of the Tibial Double-Tunnel Anterior Cruciate Ligament Complex Versus the Single Tunnel: A Biomechanical Study

Purpose: The primary objective of this study was to evaluate the difference in graft pullout forces, stiffness, and failure mode of double-bundle anterior cruciate ligament (ACL) reconstruction of the tibial insertion by use of a single tunnel compared with a double-tunnel technique with interference screw fixation. Methods: ACL reconstruction on the tibial side was performed on 40 fresh-frozen porcine knees (mean bone mineral density of 0.64 g/cm(2) measured by dual-energy x-ray absorptiometry scan), randomly assigned to the single-or double-tunnel group. Interference screw fixation of the soft-tissue graft was used for both types of tibial reconstruction. Maximum failure load, stiffness, and failure mode were recorded. Results: There was no significant difference in maximum failure load between the single-tunnel group (400 +/- 26 N) and double-tunnel group (440 +/- 20 N). Stiffness of the tibial tunnel complex was significantly higher in the double-tunnel group (76 +/- 3 N/mm) than in the single-tunnel group (62 +/- 4 N/mm) (P = .013). All but 2 grafts (38 of 40) failed by slippage of the tendon past the interference screw. Conclusions: There was significantly stiffer fixation of the tibial double-tunnel ACL complex when compared with the single tunnel. Our study did not show a different failure mode for the double-tunnel reconstruction compared with the single-tunnel reconstruction. Clinical Relevance: This study shows a biomechanical advantage with no potential deleterious side effects for fixation of the ACL with a double-tunnel technique on the tibial side.