Analysis of volumetric BMD in people with Down syndrome using DXA-based 3D modeling.

Abstract

People with Down syndrome (DS) have a lower areal bone mineral density (aBMD) estimated by dual-energy X-ray absorptiometry (DXA). However, they have smaller-sized bones, which could influence the measurements. Therefore, our objective was to determine volumetric BMD in these patients. We included 76 outpatients with DS and 76 control healthy volunteers matched for age and sex distribution. Clinical data were obtained with a standardized interview and physical exam, including age, sex, height, weight, and body mass index (BMI). aBMD was measured by dual-energy X-ray at the femoral neck (FN) and total hip (TH). The 3D-SHAPER® software (version 2.8, Galgo Medical, Barcelona, Spain) was used to derive 3D analysis from participants' hip DXA scans. DS femurs had a similar 3D geometry, compared with the femurs of controls. However, 3D analysis showed that participants with DS had smaller cortical thickness (1.84mm ± 0.17 vs. 2.02 ± 0.20mm; p < 0.0001), cortical vBMD (777 ± 49mg/cm3 vs. 809 ± 43mg/cm3; p < 0.0001), and cortical sBMD (143 ± 19mg/cm2 vs. 164 ± 22mg/cm2; p < 0.0001). After adjustment for age and BMI, all 3D measurements remained lower in DS than in controls. These differences were more marked in men than in women. vBMD decreased with age in controls and DS, but the decline was greater in DS for all 3D parameters. People with DS, particularly men, have a lower hip vBMD than the general population. Besides, vBMD declines more rapidly in DS.