Fluoride-coated high-purity magnesium cage promotes bone fusion in goat models

BACKGROUND: Cervical fusion devices made by polyether ether ketone (PEEK) cause concomitant effects which decompress the spinal cord and nerve roots. Magnesium has good biocompatibility and bioactivity as a biodegradable orthopedic implant material; however, its fusion rate is low. In this paper, we aimed to improve interbody fusion rate of high-purity magnesium (HP-Mg) by coating it with fluoride. METHODS: Fluoride-coated HP-Mg (F-HP-Mg) cages were prepared, and HP-Mg cages served as controls. We tested hydrogen release in phosphate-buffered saline (PBS) and weight loss in chromic acid. Anterior cervical discectomy and bone graft fusion (ACDF) was performed at the C2-C3 segment on goats with F-HP-Mg and HP-Mg cages to evaluate fusion score. RESULTS: Hydrogen release of F-HP-Mg cages was significantly lower than that of HP-Mg cages. Weight was significantly decreased in both types of cages after rinsing with chromic acid, while F-HP-Mg cages were more resistant to corrosion compared to HP-Mg cages. There were no significant differences in disc space height (DSH) and remaining cage volume between the two groups in computed tomography (CT) images of goat cervical spine, while cavities were found at postoperative 12 weeks and confirmed by histological staining. No complications were found, while serum aspartate aminotransaminase (AST) level was significantly higher in the HP-Mg group compared to the F-HP-Mg group. Fusion rate at 24 weeks after ACDF was significantly higher with F-HP-Mg cages. CONCLUSIONS: The use of F-HP-Mg improved histological fusion in the cervical intervertebral space of goats compared to HP-Mg and showed good biosafety.