Trabecular Bone Microarchitecture Is Deteriorated in Men With Spinal Cord Injury

Abstract

Using magnetic resonance imaging, men with spinal cord injury (n = 10) were found to have fewer trabeculae that were spaced further apart in the knee than able-bodied controls of similar age, height, and weight (n = 8). The deteriorated trabecular bone microarchitecture may contribute to the increased fracture incidence after injury. Spinal cord injury results in a dramatic decline in areal bone mineral density (aBMD) and a marked increase in lower extremity fracture; however, its effect on trabecular bone microarchitecture is unknown. The purpose of this study was to determine if trabecular bone microarchitecture is deteriorated in the knee of men with long-term, complete spinal cord injury. Apparent bone volume to total volume (appBV/TV), trabecular number, (appTb.N), trabecular thickness (appTb.Th), and trabecular separation (appTb.Sp), measures of trabecular bone microarchitecture, were assessed in the distal femur and proximal tibia of men with long-term (>2 years) complete spinal cord injury (SCI; n = 10) and able-bodied controls (CON; n = 8) using high-resolution magnetic resonance imaging. Proximal tibia and arm aBMD were determined using DXA. Independent t-tests were used to assess group differences in anthropometrics and bone parameters. Pearson correlation analysis was used to assess the relationships among trabecular bone microarchitecture, aBMD, and time since injury. There were no group differences in age, height, or weight; however, the distal femur and proximal tibia of SCI had 27% and 20% lower appBV/TV, 21% and 20% lower appTb.N, and 44% and 33% higher appTb.Sp, respectively (p < 0.05). The distal femur of SCI also had 8% lower appTb.Th (p < 0.05). Whereas arm aBMD was not different in the two groups, proximal tibia aBMD was 43% lower in SCI. In SCI and CON combined, aBMD was correlated with appBV/TV (r = 0.62), appTb.N (r = 0.78), and appTb.Sp (r = -0.82) in the proximal tibia (p < 0.05). Time since injury was more strongly correlated with appTb.N (r = -0.54) and appTb.Sp (r = 0.56) than aBMD (r = -0.36) in the distal tibia, although none of the relationships were statistically significant (p > 0.05). Men with complete spinal cord injury have markedly deteriorated trabecular bone microarchitecture in the knee, which may contribute to their increased fracture incidence.