Comparison of torsional strengths of bioabsorbable screws for anterior cruciate ligament reconstruction.

The goals of this study were to evaluate torsional strength and modes of failure in commercially available bioabsorbable interference screws and to test the effect of screw diameter on torsional strength when screws become jammed during insertion. We tested the Arthrex, BioScrew, Endo-Fix, Phantom, and Sysorb screws, all 20 mm in length. Four major modes of failure were encountered. Analysis of variance revealed that both screw type and diameter had a significant effect on failure torque. The Endo-Fix 7-mm screw had the lowest failure torque (1.07 +/- 0.18 N x m) and the Sysorb 8-mm screw had the highest (5.23 +/- 0.24 N x m). The Sysorb was significantly stronger than all the other screws. The failure torques were within the range that has been reported for manual screw insertion. We concluded that technical factors, which can affect insertion torque, assume particular importance with the use of bioabsorbable interference screws.