Bone Abstracts

The prevalence of fractures in white children in South Africa is double that of black children (1). White males who fractured were shown to be more physically (2). The aim of this study was to compare the bone mass and geometry measures using peripheral quantitative computed tomography (pQCT) and dual energy x-ray absorptiometry (DXA) in black and white children with and without a history of fracture to determine the risk factors for fractures.

Lifetime fractures were recorded retrospectively in subjects from the Birth To Twenty cohort up to the age of 17 years. The findings of fracture and bone mass using DXA to those findings of fracture and bone geometry using pQCT were compared.

Outcome measures for DXA were total body less head bone area (TBLH BA), total body less head bone mineral content (TBLH BMC) and site-specific measurements of bone area (BA) and BMC at the radius (R), hip (H), hip neck (HN) and lumbar spine (LS). Outcome measures for pQCT were trabecular volumetric (v) BMD and total cross-sectional area (CSA) at the distal site (4%), and cortical vBMD, cortical CSA, total CSA and the polar stress-strain index (SSI) at the proximal site of each bone (38% tibia, 65% radius). Within groups stratified by sex and ethnicity, Mann–Whitney tests were used to compare measures between subjects who had fractured and those who had not.

White males who fractured have greater bone area and BMC, measured by DXA, but no associations were found among females or black males. White males who fractured had greater total CSA at the distal radius and at the proximal tibia. Black males who had fractured had lower trabecular vBMD at the distal radius than non-fracturing black males. Among females, no associations were found between any pQCT measure and fracture. Cortical CSA, cortical vBMD and SSI were not associated with fracture in any group.

In conclusion, fractures were associated with greater bone size at certain sites in white males as measured by both DXA and pQCT. Physical activity and other environmental factors might therefore be more important than bone structure in determining fracture risk in healthy children.

Disclosure: The authors declared no competing interests.