Failure forces of different interspinous vertebropexy techniques.

Abstract

Background context: Challenges of vertebropexy such as spinous process fractures and tendon pull-out under high flexion loads need to be further investigated to ensure long-term stability of the construct.

Purpose: Vertebropexy is a technique using a tendon as a posterior tension band to stabilize vertebral segments. Failure modes include pull-out or spinous process fractures under high flexion loads. This study simulates physiological risk loads in a biomechanical test to compare different interspinous vertebropexy techniques STUDY DESIGN: : Biomechanical cadaveric study.

Methods: EIGHTEEN VERTEBRAL SEGMENTS WERE STABILIZED USING BOVINE FLEXOR TENDONS WITH THREE METHODS: "Tunnel only" (twice through spinous process holes), "Tunnel + cortical wrapping" (once through holes, once around spinous processes), and "Cortical wrapping only" (twice around spinous processes). Segments were subjected to cyclic, load-controlled flexion until failure. Force differences, bone failure modes, and the impact of bone quality on spinous process resistance were evaluated and compared.

Results: The "Cortical wrapping only" technique achieved the highest mean torque (25.8 Nm), significantly outperforming the "Tunnel only" technique (13.4 Nm; p=0.024). The "Tunnel + cortical wrapping" technique (18.1 Nm) showed no significant difference from either "Tunnel only" or "Cortical wrapping only" (p=0.700; p=0.190). Bone failure modes, such as tendon cutting into bone and spinous process fractures, were consistent across technique. Bone density influenced failure resistance only in techniques involving cortical wrapping.

Conclusions: The "Cortical wrapping only" method doubled the failure loads compared to the "Tunnel only" method while avoiding common failure modes like spinous process fractures. Additionally, bone density is a crucial factor to consider when using cortical bone as an abutment for the vertebropexy loop.

Clinical significance: This study proposes alternative vertebropexy techniques to enhance spinal stabilization and minimize failure risks.