Modeling of cross-sectional bone size, mass and geometry at the proximal radius: a study of normal bone development using peripheral quantitative computed tomography.

It is becoming increasingly accepted that bone size is an important determinant of bone mass. Studies on the development of bone size may therefore promote a better understanding of the basis of diseases which are due to low bone mass. Here, we characterize the temporal changes in cross-sectional bone size, geometry and mass at the radial diaphysis in healthy subjects from 6 to 40 years of age (n = 469; 273 females). Peripheral quantitative computed tomography was used to measure total and cortical cross-sectional area, bone mineral content (BMC) and volumetric bone mineral density (BMD) at the site of the forearm whose distance from the ulnar styloid process corresponded to 65% of forearm length. Over the age range of the study, total cross-sectional area increased by 39 mm2 (50%) in females and by 85 mm2 (116%) in males. Cortical area increased to a similar extent in both sexes. Between 6-7 years and adulthood, BMC increased by 52 mg/mm (111%) in females and by 73 mg/mm (140%) in males and was significantly higher in males after the age of 15 years. Volumetric BMD increased by 246 mg/cm3 (48%) in females but by only 132 mg/cm3 (23%) in males and was significantly higher in women than in men. In summary, these data show that BMC in men is higher than in women, because periosteal modeling continues longer in boys than in girls. Volumetric BMD is higher in women, partly because the size of the marrow cavity does not increase in girls as it does in boys.