Radial bone mineral density and estimated rates of change in normal Scottish women: assessment by peripheral quantitative computed tomography.

This study examines normative bone mineral density (BMD) data, as measured by peripheral quantitative computed tomography of the ultradistal radius, in 332 Scottish women aged 18-90 years, comparing it to a recently reported normal German population. The normative Scottish data were higher in almost all decades compared with German counterpart, percentage differences being +0.002%-+21.6% for total (Qtot), and -0.06%-+31.9% for trabecular (Qtrab) BMD. Differences in calibration of the Stratec XCT-960 and XCT-900 systems are thought to be largely responsible for these differences. Estimated age-related changes were determined in the Scottish population. A cubic regression model best fitted age-related changes in the whole population, and changes as a function of years postmenopause in the postmenopausal subgroup, for Qtot, subcortical (Qscort), and cortical (Qcort) BMD, whereas a parabolic regression model best fitted corresponding changes in Qtrab BMD. Percentage age-related changes (5 years: 10 years postmenopause) in Qtot (-0. 79%-1.12%/year) and Qscort (-0.72%-1.12%/year) were greater than Qtrab (-0.53%-0.56%/year) in the early postmenopausal years. Maximum age-related changes were found at 20 years postmenopause for Qtot (-1.36%/year), Qscort (-1.39%/year), and Qcort (-1.39%/year). This study has highlighted variation in normative data derived by different Stratec pQCT systems. The estimated age-related changes suggest that early postmenopausal bone loss preferentially affects subcortical rather than trabecular bone at the radius.