Interference screw fixation using bioabsorbable screw as void filler

We evaluated interference screw fixation in a plug-tunnel construct using bioabsorbable screws as void fillers with different percentages of the screw removed. Nine-millimeter tunnels in a closed-cell foam block were filled with a 10-mm bioabsorbable screw, and 10-mm revision tunnels were placed in parallel with tunnel overlap resulting in removal of 10%, 25%, or 50% of the screw diameter. Synthetic bone plugs were fashioned to fit 10-mm tunnels. In all groups, the plugs were secured in standard interference fixation with a 9-mm metal screw between the void-filling bioabsorbable screw and plug. Failure loads for the control group (no revision tunnel) averaged 926 +/- 44 N, 10% (1024 +/- 129 N) and 25% (932 +/- 129 N) groups were not significantly different; failure load in the 50% diameter group (780 +/- 72 N) was significantly lower than all other groups (p < 0.001). Using a bioabsorbable screw as void filler provided mean load to failure not different from that of standard reconstruction when 10 and 25% of the diameter of the void-filling screw was removed. Load to failure was significantly lower when 50% of the void-filling screw diameter group was removed. This may be applicable in anterior cruciate ligament reconstruction where a previous tunnel void has to be addressed.