Comparison of Initial Mechanical Properties of 4 Hamstring Graft Femoral Fixation Systems Using Nonpermanent Hardware for Anterior Cruciate Ligament Reconstruction: An In Vitro Animal Study

Abstract

Purpose: To compare the initial mechanical characteristics of 4 systems used to fix tendons to the femur during anterior cruciate ligament reconstruction. Methods: A total of 32 porcine femurs were used to study the following fixation systems: Bioabsorbable interference screw (Stryker, Kalamazoo, MI), Bio-Transfix Cross-pin (Arthrex, Naples, FL), Biosteon Cross-pin (Stryker), and a fixation technique based on wrapping the graft around the femoral condyle itself, thus allowing it to be fixed in place without the use of any hardware. The mechanical characteristics of each system were obtained by a preconditioned failure tensile test. Results: The yield load values (990.9 ± 242.6 N for Bio-Transfix, 905.1 ± 158.8 N for Biosteon Cross-pin, 684.4 119.7 N for the without-hardware system (WHS), and 369.4 ± 120.1 N for the interference screw) revealed significant differences between the techniques that used cross-pins and the other 2 techniques (P < .006) on the one hand, and between the without hardware technique and the interference screw (P < .004) on the other. The stiffness of the 2 cross-pin fixation systems (117.6 ± 22.5 N for Bio-Transfix and 112.6 ± 22.5 N for Biosteon) was greater (P < .01) than those of the other systems (79.4 ± 15.2 N for the WHS and 68.5 ± 13 N for the interference screw). Conclusions: The initial biomechanical properties of the 2 cross-pin fixation systems proved to be superior to those of the other 2 systems studied. The WHS fixation system exhibited better mechanical properties than its interference screw counterpart. Clinical Relevance: The better initial mechanical characteristics encountered using the BioTransfix and Biosteon Cross-pin systems indicate that these systems are better equipped to bear the loads generated by aggressive rehabilitation. The WHS fixation system provides an alternative to interference screw fixation.