Kinematics of a Novel Canine Cervical Fusion System

Objective The aim of this study was to determine the biomechanical behaviour of a novel distraction–fusion system, consisting of an intervertebral distraction screw, pedicle locking screws and connecting rods, in the canine caudal cervical spine. Study Design Biomechanical study in cadaveric canine cervicothoracic (C3–T3) spines (n = 6). Cadaveric spines were harvested, stripped of musculature, mounted on a four-point bending jig, and tested using non-destructive four-point bending loads in extension (0–100 N), flexion (0–60 N) and lateral bending (0–40 N). Angular displacement was recorded from reflective optical trackers rigidly secured to C5, C6 and C7. Data for primary and coupled motions were collected from intact spines and following surgical stabilization (after ventral annulotomy and nucleotomy) with the new implant system. Results As compared with the intact spine, instrumentation significantly reduced motion at the operated level (C5-C6) with a concomitant non-significant increase at the adjacent level (C6-C7). Conclusion The combination of a locking pedicle screw-rod system and intervertebral spacer provides an alternative solution for surgical distraction–stabilization in the canine caudal cervical spine and supports the feasibility of using this new implant system in the management of disc-associated cervical spondylomyelopathy in dogs. The increase in motion at C6-C7 may suggest the potential for adjacent level effects and clinical trials should be designed to address this.