Evolgate Fixation of Doubled Flexor Graft in Anterior Cruciate Ligament Reconstruction: Biomechanical Evaluation with Cyclic Loading

Abstract

Background The weakest points in hamstrings anterior cruciate ligament reconstruction are its points of fixation, especially on the tibial side. Methods for graft fixation to bone should be strong enough to avoid failure, stiff enough to restore load-displacement response, and secure enough to resist slippage under cyclic loading. Hypothesis Biomechanical properties of the interference screw can be improved by reinforcing the walls of the tunnel with a metal spiral (Evolgate fixation). Study Design Controlled laboratory study. Methods Three paired tests were performed using common digital extensor bovine tendons fixed to porcine tibias with interference screw, Intrafix, and Evolgate; critical graft fixation conditions were simulated by applying subsequent cycles to the graft before loading the graft until failure. Results The strength, stiffness, and resistance to slippage of the Evolgate were significantly higher than those of the interference screw; the ultimate failure load of the Evolgate was significantly higher than that of the Intrafix (1058 ± 130 N and 832 ± 156 N, respectively; P =. 02). No statistically significant differences were found between Evolgate and Intrafix regarding the stiffness and slippage under cyclic load. Conclusion Evolgate fixation seems to be stronger, stiffer, and more resistant to slippage than is interference screw fixation of similar length, and it is stronger but not stiffer than Intrafix. Clinical Relevance The Evolgate provides structural properties that seem to be appropriate for an intensive rehabilitation after anterior cruciate ligament reconstruction using a doubled semitendinosus and gracilis graft.