Time course changes to structural, mechanical and material properties of bone in rats after complete spinal cord injury

Objective: Characterise the spatiotemporal trabecular and cortical bone responses to complete spinal cord injury (SCI) in young rats. Methods: 8-week-old male Wistar rats received T9-transection SCI and were euthanised 2-, 6-, 10- or 16-weeks post-surgery. Outcome measures were assessed using micro-computed tomography, mechanical testing, serum markers and Fourier-transform infrared spectroscopy. Results: The trabecular and cortical bone responses to SCI are site-specific. Metaphyseal trabecular BV/TV was 59% lower, characterised by fewer and thinner trabeculae at 2-weeks post-SCI, while epiphyseal BV/TV was 23% lower with maintained connectivity. At later-time points, metaphyseal BV/TV remained unchanged, while epiphyseal BV/TV increased. The total area of metaphyseal and mid-diaphyseal cortical bone were lower from 2-weeks and between 6- and 10-weeks post-SCI, respectively. This suggested that SCI-induced bone changes observed in the rat model were not solely attributable to bone loss, but also to suppressed bone growth. No tissue mineral density differences were observed at any time-point, suggesting that decreased whole-bone mechanical properties were primarily the result of changes to the spatial distribution of bone. Conclusion: Young SCI rat trabecular bone changes resemble those observed clinically in adult and paediatric SCI, while cortical bone changes resemble paediatric SCI only.

Automated summary

This study aimed to characterize the spatiotemporal trabecular and cortical bone responses to complete spinal cord injury (SCI) in young rats. The results showed that the bone responses to SCI are site-specific, with significant changes observed in trabecular and cortical bone at different time points. The findings suggest that the observed bone changes in the rat model are not solely attributed to bone loss, but also to suppressed bone growth and altered spatial distribution of bone. These findings have implications for understanding the bone changes associated with SCI in both adult and pediatric populations.