Metacarpal index and bone mineral density in healthy African-American women.

Bone mineral density (BMD) reference data of non-Caucasian women is scarce but greatly needed for African-American women. The objective of this study was to establish a metacarpal normative reference database for African-American women using digital X-ray radiogrammetry (DXR) and hand radiographs and compare these values to existing Caucasian data. Two hundred and fifty healthy African-American women between the ages of 20 and 79 years old, 14 of whom were excluded, were recruited to participate from four different clinical sites. The study population was recruited in approximately equal number into the following groups: 20-29, 30-39, 40-49, 50-59, 60-69 and 70-79 years of age. A radiograph was acquired of each subject's non-dominant hand. The radiographs were scanned and analyzed using radiogrammetric techniques, and the BMD, MCI (Metacarpal Index), bone width and cortical thickness were calculated. The regression curve that best fit the data was a second order polynomial. The BMD and MCI of young adult women (20-40 years of age) were used to calculate T-score parameters. The young reference BMD and MCI with their associated standard deviations were found to be 0.6045 g/cm2+/-0.0529 g/cm2 and 0.5096 and 0.0792, respectively. However, the MCI was found to be approximately 2.5% lower (-0.0118) compared to Caucasian women. The African-American metacarpal BMD was found to be 3.5% (0.0207 g/cm2) higher across all ages when compared to existing Caucasian reference data acquired in a similar way. The differences were found to be entirely due to larger bone size, cortical diameter and bone width in the African-American women.