DETERMINATION OF FIXATION STRENGTH OF LARGE-DIAMETER INTERFERENCE SCREWS

Small-diameter interference screws are a widely used method of securin g bone-tendon grafts during anterior cnrciate ligament reconstructive procedures. Recent reports document tunnel widening and subsequent los s of fixation, leading to a need for alternative fixation methods. In cadaver tissue, the fixation strength of large-diameter (11-, 13-, and 15-mm) interference screws was tested and compared with that of clini cally used 9-mm diameter screws. Patellar-tendon sections were fashion ed into three grafts, each with bone plugs measuring 10 x 20 x 7.5 mm. Tunnels were created in the epiphyseal bone of the femurs and tibias, resulting in gap sizes of 4.5-, 6.5-, 8.5-, and 10.5-mm for the 9-, 1 1-, 13-, and 15-mm diameter screws, respectively. Grafts were pulled f rom the tunnel at a rate of 51 cm/min. Average fixation strengths were 276, 302, 328, and 328 N for the 9-, 11-, 13-, and 15-mm screws, resp ectively No significant difference existed between the fixation streng ths (ANOVA, P less than or equal to .05).