Comparison of ACL fixation devices using cadaveric grafts

Abstract

We evaluated two newer forms of femoral fixation of hamstring grafts for anterior cruciate ligament reconstruction, the Endobutton direct (Smith and Nephew, Andover, MA) and Femoral intrafix (Depuy Mitek, Raynham, MA), and compare them to devices that have been evaluated in the literature, the AXL Crosspin (Biomet, Warsaw, IN) and Biotransfix II (Arthrex, Naples, FL). Paired hamstring tendon allografts were fixed in the femoral tunnel of 24 cadaveric bovine knees (6 per group) according to each device's specifications. The free ends (tibial sides) were fixed to the materials testing machine via custom-made cryo-clamps. In Phase I, single load to failure and stiffness were evaluated, and in Phase II, peak displacement was evaluated while cyclic loading was performed over 1000 cycles. One-way analyses of variance were performed to test for differences between groups. There were no significant differences in failure load (p = 0.42) or stiffness (p = 0.39) between the fixation devices. There was also no significant difference in peak displacement measured during the cyclic loading phase (p = 0.32). Our findings suggest that the newer generation devices, Endobutton direct and Femoral intrafix, have similar strength in single load to failure and similar peak displacement during cyclic loading as compared with clinically proven Crosspin techniques. These newer devices, which are designed to accommodate for more anatomic femoral tunnel placement, may provide a reasonable alternative without compromising biomechanical properties.