Biomechanical Analysis of Suture Bridge Fixation for Tibial Eminence Fractures

Abstract

To perform a biomechanical analysis of suture bridge fixation for tibial eminence fractures using PushLock anchors (Arthrex, Naples, FL) and compare it with traditional suture fixation and screw fixation. This study used 24 porcine knees, divided into 3 comparison fixation groups: PushLock suture bridge fixation, screw fixation, and suture fixation. Each knee was dissected of all soft tissue, leaving only the anterior cruciate ligament. A tibial eminence fracture was created with disruption of the posterior hinge, and each knee was fixed with a randomly assigned fixation technique. After fixation, each knee underwent 2 phases of biomechanical testing. The initial cyclic dynamic phase assessed the displacement change after 200 cycles (in millimeters) and initial stiffness (in Newtons per millimeter) of the fixation construct. After completion of dynamic testing, each specimen underwent a single tensile failure test load to assess ultimate failure load (in Newtons) and displacement (in millimeters) to ultimate failure. There was a significant difference for the load-to-failure outcome variable among treatment groups (P = .004 by analysis of variance, 1 - β = 0.851). Mean ultimate failure load borne by the PushLock fixation group was statistically significantly higher in comparison with the screw (P = .007) and suture (P = .017) fixation groups. For the cyclical testing, the primary outcome variable of displacement change after 200 loading cycles failed to show a significant difference among the 3 groups (P = .412). Suture bridge fixation with PushLock anchors is a new and effective surgical technique for the treatment of displaced tibial eminence fractures. By use of a high-bone density animal model, our results suggest that this suture bridge construct provides superior fixation with regard to ultimate failure load compared with standard screw fixation and suture fixation. The suture bridge technique provides another fixation option for displaced tibial eminence fractures with comparable, and in some instances superior, biomechanical properties to screw fixation and suture fixation.