Five-Year Longitudinal Bone Evaluations in Individuals With Chronic Complete Spinal Cord Injury

Background/Objectives: Knowledge of spinal cord injury (SCI) bone changes has been derived primarily through cross-sectional studies, many of which are controvertible. Longitudinal studies are sparse, and long-term longitudinal chronic studies are unavailable. The objective of this study was to provide a clearer perception of chronic longitudinal bone variations in people with complete SCI. Methods: Bone status of 31 individuals with chronic, complete SCI was assessed twice using dual-energy x-ray absorptiometry at an average interval of 5.06 +/- 0.9 years. Because the sample of women was small (4), the primary analyses of change and comparisons of those with paraplegia vs tetraplegia were confined to the male participants. Results: Spine Z-scores showed a significant increase (P < 0.0001). The average Z-scores, initial and follow-up, were within the normal range. Hip Z-scores also showed a significant increase (P < 0.0001), and hip bone mineral density (BMD) increased in 48% of the participants. Knee BMD and lower extremity total bone mineral showed significant decreases (P < 0.003 and P < 0.02, respectively), but increases were seen in 33% and 26% at the respective sites. Individuals with tetraplegia had significantly lower values across all regions (P < 0.0001), and changes were significantly different compared with paraplegia (P < 0.0001). Bone values and changes in men vs women, despite the small sample of women, showed highly significant differences (P < 0.003-0.002). Conclusion: Chronic effects of complete SCI do not exclusively result in continued loss of BMD or a static state of lowered BMD; gain in BMD may occur. The nature and magnitude of the effects of complete SCI on BMD vary by site, with sex and level of injury, which has implications for treatment and its assessment.