Tibial Tunnel Widening in ACL Reconstruction-Comparing Two Bioscrews: A Prospective Randomized Clinical Trial

Widening of the single tibial tunnel following ACL surgery with quadrupled hamstrings autograft may contribute to failure of the graft and/or present technical challenges secondary to bone loss in a revision setting (Getelman, 1999). As such, efforts should be made to minimize the incidence and magnitude of tibial tunnel widening without sacrificing the biomechanical properties of the graft construct. The purpose of this investigation is to examine the tibial tunnel widening relationship between bioabsorbable interference screws composed of poly-L-lactic acid (PLLA) alone and composite bioabsorbable interference screws composed of poly-L-lactic acid embedded with beta tricalcium phosphate (PLLA+TCP) utilized as tibial fixation devices.

Specifically the study has the following objectives: 1) To quantify the extent of tibial tunnel enlargement at 3-, 6- and 12-months post ACL reconstruction with autogenous quadrupled hamstring graft; 2) To determine if the incorporation of beta tricalcium phosphate to the bioabsorbable interference screw alters the observed magnitude of tunnel widening; 3) To hypothesize mechanisms for any observed differences between tibial fixation devices; and 4) To correlate tibial tunnel widening with clinical outcome status. It is hypothesized that the PLLA+TCP bioabsorbable interference screw will not be associated with a reduction in tibial tunnel widening around the implant but rather between the implant and articular surface, compared to the PLLA alone screw. It is also hypothesized that there will be no effect of observed tunnel widening on clinical outcomes or graft failure rates.