Effects of interference fit screw length on tibial tunnel fixation for anterior cruciate ligament reconstruction.

Graft-tunnel mismatch during arthroscopically assisted anterior cruciate ligament reconstruction using the central-third patellar tendon results in less than 20 mm of bone plug remaining in the tibial tunnel. We decided to evaluate the strength of bone plug fixation using interference fit screws that were less than 20 mm in length. Biomechanical testing was performed on 48 porcine hindquarters using 9-mm diameter interference fit screws that measured 12.5, 15, and 20 mm in length. No significant difference was noted between the different-length screws for insertion torque, divergence, stiffness, displacement, or load to failure. We believe, therefore, that comparable graft fixation can be achieved in the tibial tunnel using 9-mm diameter interference fit screws that are less than 20 mm long, and that these shorter screws may be useful in cases of graft-tunnel mismatch.