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

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