Biomechanical Comparison of Polyether ether ketone and Titanium Rods for Novel Posterior Lumbar Spine Fusion Surgery in a Canine Model

Abstract

Abstract Background: Previous studies have demonstrated the benefits of posterior lumbar spine fusion with orthotopic paraspinal muscle-pediculated bone flaps. However, non-union due to poor mechanical support remains a concern. Flexible devices, such as PEEK, are superior to conventional rigid devices in facilitating union and reducing adjacent segmental movement. Here, we assessed whether PEEK rods can accelerate fusion and reduce adjacent segmental movement to prevent adjacent segment disease. Methods: Thirty-two mongrel dogs were assigned randomly into two groups for lumbar fusion surgery: titanium rods (control group; n=16); PEEK rods (treatment group; n=16). Animals were killed 8 or 16 weeks after surgery. The lumbar spines were harvested, and spinal changes were analyzed by manual palpation, gross examination, 3D motion tests, 3D-CT reconstruction (for rate of fusion), and µCT (for 3D structures of the fusion masses). Immunohistochemistry was used to examine the expression of BMP-2 and VEGF. Results: The results indicated no significant differences in the lumbar spine of the control and treatment groups in terms of manual palpation, gross examination, 3D-CT reconstruction or range of movement (P>0.05). However, BMP-2 and VEGF expression was higher in the treatment group than in the control group at 8 weeks (BMP-2, 106.7 ± 8.8 vs. 90.4 ± 9.6, respectively, P<0.05; VEGF: 71.1 ± 10.6 vs. 58.5 ± 12.4, respectively; P<0.05). Results from the µCT showed better 3D structures of the fusion masses and higher bone quality in the treatment group (P<0.05). Conclusion: PEEK rods increase the rate and quality of fusion but provide a similar range of adjacent segment movement as titanium rods.