Racial Differences in Bone Microarchitecture and Estimated Strength at the Distal Radius and Distal Tibia in Older Adolescent Girls: a Cross-Sectional Study.

BACKGROUND: Previous studies have demonstrated that an individual's race and ethnicity are important determinants of their areal bone mineral density (aBMD), assessed by dual-energy X-ray absorptiometry. However, there are few data assessing the impact of race on bone microarchitecture and strength estimates, particularly in older adolescent girls and young adults. We hypothesized that bone microarchitecture and strength estimates would be superior in Blacks compared to White and Asian American adolescent girls and young adults of similar age based on reports of higher aBMD in Blacks.

METHODS: We assessed BMD using dual-energy X-ray absoptiometry (DXA), bone microarchitecture at the distal radius and distal tibia using high-resolution peripheral quantitative computed tomography (HRpQCT) and estimated measures of bone strength using micro-finite element analysis (FEA) in 35 White, 15 Asian American, and 10 Black girls 14-21 years.

RESULTS: After controlling for height, most DXA measures of aBMD and aBMD Z scores were higher in Black girls compared with Whites and Asian Americans. HRpQCT and FEA showed that at the distal radius, Blacks had greater cortical perimeter, cortical area, trabecular thickness, trabecular BMD, estimated failure load, and stiffness than the other two groups. For the distal tibia, trabecular number and BMD were higher in Blacks than Asian Americans.

CONCLUSIONS: Particularly at the distal radius, adolescent and young adult White and Asian American girls have less favorable bone microarchitecture and lower bone strength than Blacks, possibly explaining the lower risk of fracture seen in Blacks.

LEVEL OF EVIDENCE: Level II.