FAILURE FORCES OF DIFFERENT INTERSPINOUS VERTEBROPEXY TECHNIQUES

Vertebropexy is a surgical technique designed to stabilize vertebral segments using tendons as posterior tension bands. However, methods such as looping the graft through a tunnel in the spinous process, are prone to clinical failure modes, including graft pullout and spinous process fractures under high flexion loads. This study aimed to simulate physiological risk loads in a biomechanical setup and evaluate new vertebropexy techniques. Eighteen cadaveric vertebral segments were stabilized using bovine flexor tendons in three configurations: (1) “Tunnel only” (twice through spinous process holes), (2) “Tunnel + cortical wrapping” (once through holes, once around spinous processes), and (3) “Cortical wrapping only” (twice around spinous processes). The specimens underwent cyclic, load-controlled flexion tests until failure. Force and torque resistances, bone failure patterns, and the influence of bone quality on technique efficacy were analyzed. The “Cortical wrapping only” technique demonstrated the highest load resistance (mean torque: 25.8 Nm), significantly surpassing the “Tunnel only” method (mean torque: 13.4 Nm; p < 0.05). The hybrid “Tunnel + cortical wrapping” technique (mean torque: 18.1 Nm) showed no significant differences compared to either alternative (p > 0.1). Bone failure modes, such as tendon cuts into bone and spinous process fractures, were comparable between the techniques. Bone density played a role notably in techniques based on cortical wrapping. Our biomechanical model reliably replicated clinical failure scenarios. Among the examined vertebropexy techniques, the “Cortical wrapping only” configuration significantly improved load resistance, doubling the failure load values of the “Tunnel only” method. Bone quality remains a critical consideration in vertebropexy, particularly for techniques involving cortical support. Different VPX techniques: (A) Tunnel only, (B) Tunnel + cortical wrapping, (C) Cortical wrapping only