A Biomechanical Comparison of Initial Fixation Strength of 3 Different Methods of Anterior Cruciate Ligament Soft Tissue Graft Tibial Fixation: Resistance to Monotonic and Cyclic Loading

Background Tibial fixation of soft tissue grafts continues to be problematic in the early postoperative period after anterior cruciate ligament reconstruction. Hypothesis No differences exist for resistance to slippage of soft tissue grafts fixed with CentraLoc, Intrafix, or 35-mm bioabsorbable interference screws. Study Design Controlled laboratory study. Methods Bovine tibia and hoof extensor tendons were divided into 3 matched groups with 12 tibia and 12 extensor tendons in each group. Within each group, 6 specimens underwent monotonic loading to failure (1 mm/s), and 6 underwent cyclic loading (10 000 cycles, 125-325 N, 1 Hz). Results No statistically significant differences were noted in mean load to failure or stiffness. The mean load to failure (and stiffness) for the 3 types of fixation were as follows: bioabsorbable interference screw, 631.6 ± 130.1 N (88.17 ± 6.79 N/mm); Intrafix, 644.3 ± 195.2 N (81.65 ± 16.5 N/mm); and CentraLoc, 791.1 ± 72.7 N (77.89 ± 7.07 N/mm). The slippage rates under cyclic loading for the 3 types of fixation were bioabsorbable interference screw, 0.336 ± 0.074 µm/cycle; Intrafix, 27.2 ± 31.6 µm/cycle; and CentraLoc, 0.0355 ± 0.0046 µm/cycle. In this model, CentraLoc proved statistically superior in resistance to cyclic loading compared with the bioabsorbable interference screw (P < .05) and Intrafix (P < .0001). The bioabsorbable interference screw proved statistically superior to Intrafix in resistance to cyclic loading (P < .05). Conclusions In this bovine model, CentraLoc and bioabsorbable interference screws provided superior resistance to cyclic loading compared with Intrafix. Clinical Relevance CentraLoc and bioabsorbable interference screws showed superior resistance to cyclic loading, which may indicate an increased resistance to clinical failure.