Interactive effects of tunnel dilation on the mechanical properties of hamstring grafts fixed in the tibia with interference screws.

The effect of dilation of the tibial tunnel on the strength of hamstring graft fixation using interference screws was evaluated. In all, 28 RCI screws were tested in male human tibia-hamstring constructs with tibial tunnels reamed or dilated to the respective size of the graft diameter. Dilation of the tibial tunnel failed to significantly enhance hamstring fixation. Grafts secured in dilated tunnels displayed an 11% greater resistance to the initiation of graft slippage (174+/-112 N) compared to their undilated controls (156+/-77 N, P=0.63). Dilation of the tibial tunnel increased the failure load by an average of 4%, independent of screw diameter (dilated specimens: 360+/-120 N, controls: 345+/-88 N, P=0.74). Biomechanical research on the effect of tibial tunnel dilation in hamstring fixation has not provided satisfactory evidence as to the benefits of this additional surgical step during anterior cruciate ligament (ACL) reconstruction.