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/cm² 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.