Bone Mineral Density and Content: Dual Energy X‐ray Absorptiometry versus Peripheral Quantitative Computed Tomography

Abstract

Dual energy x-ray absorptiometry (DXA) assesses bone mineral density (BMD) and content (BMC), but does not differentiate between cortical (Cr) and trabecular (Tb) bone, independent contributors to bone strength and fracture risk. Peripheral quantitative computed tomography (pQCT) provides a 3-D image of bone and assesses Tb and Cr bone. We compared total (To) BMC, TbBMC, volumetric (v) BMD, and TbBMD of the 4% distal tibia, and ToBMC, CrBMC, vBMD, and CrBMD of the 33% midshaft femur using pQCT to lumbar spine (Sp), hip, and femoral neck (FN) BMD and BMC from DXA in healthy, postmenopausal women. Tibia pQCT BMC and BMD measures were highly correlated (p<0.0001) with DXA measures, while femur pQCT was related to hip and FN BMC and BMD DXA measures, but not spine BMD DXA (Table 1). Table 1. Correlation Coefficients between DXA and pQCT Measures (N=187) Skeletal heterogeneity between axial and peripheral sites suggests that BMD measures from one site are not a good proxy for another BMD site. Further studies are needed to determine the relevance of peripheral densitometry data. Supported by NIAMS/NIH (AR046922); USDA, ARS, WHNRC.