The evolgate: A method to improve the pullout strength of interference screws in tibial fixation of anterior cruciate ligament reconstruction with doubled gracilis and semitendinosus tendons

Purpose: The goal of the study was to investigate the biomechanical properties of a new device for tibial fixation in arthroscopic anterior cruciate ligament reconstruction using doubled semitendinosus and gracilis tendons. Type of Study: Biomechanical study. Methods: This study compares the initial pullout strength, stiffness, and failure modes of 7 pairs of 4-strand human semitendinosus and gracilis grafts fixed to porcine tibias using either the Evolgate (Citieffe, Bologna, Italy) or 1 round threaded titanium interference screw. Structural tests of the graft fixation method tibia complexes were performed using a materials testing machine (MTS Bionix 855, Minneapolis, MN) at a strain rate of 50 mm/second. Results: The mean failure load was 1,237+/-191 N for the Evolgate and 537+/-65 N for the interference screw (P<.05) and the mean stiffness was 168 +/- 37 N/m for the Evolgate and 105 +/- 17 N/m for the interference screws (P <=.05). Although in all the cases fixed with the Evolgate failure occurred because of tendon rupture inside the tibial tunnel close to the fixation device, in 4 of the 7 cases fixed with interference screws, failure occurred because of tendon slippage at the fixation site. Conclusions: These results indicate that initial pullout strength of hamstring tendon graft interference screw fixation can be significantly increased using the Evolgate. In fact, because the screws purchase only in the cancellous bone, the Evolgate reinforces the walls of the tibial tunnel with a titanium involute, avoiding the loss of fixation strength related to the low density of the cancellous bone of the proximal metaphysis of the tibia.