Correlation Between Duration From Injury and Bone Mineral Density in Individuals With Spinal Cord Injury.

Objective: To investigate the correlation between bone mineral density (BMD) and duration of injury in individuals with spinal cord injury (SCI).

Methods: Patients with SCI who visited the outpatient department between January 2009 and January 2019 were enrolled. Patients' most recent dual energy X-ray absorptiometry images were reviewed. According to the 2007 International Society for Clinical Densitometry guidelines, vertebrae with a local structural change were excluded when deriving spine BMD. If one or no vertebra is suitable for evaluation, spine BMD was judged as "improper for assessment". Correlation analysis was performed between duration from injury and BMD Z-scores of the hip and spine.

Results: Among 83 individuals with SCI, the spines of 44 were judged as improper for assessment. The correlation analysis showed a significant negative relationship between the duration from injury and femur neck BMD (r=-0.40, p<0.01) and total proximal femur BMD (r=-0.39, p<0.01). However, no significant correlation was found between the duration from injury and spine BMD Z-score.

Conclusion: The duration of SCI correlated with hip BMD, but not with spine BMD. Further, more than half of the individuals with SCI could not undergo spinal assessment due to local structural changes. Therefore, spine BMD measurement is not an appropriate method for predicting future fracture risk in those with SCI.