Measurement of bone mineral density at the spine and proximal femur by volumetric quantitative computed tomography and dual-energy x-ray absorptiometry in elderly women with and without vertebral fractures

Abstract

The goal of this study was to determine the effect of vertebral fracture status on trabecular bone mineral density (BMD) measurements obtained in the proximal femur and spine by helical volumetric quantitative computed tomography (vQCT). The study population consisted of 71 Italian women (average age 73 ± 6) years. This group included 26 subjects with radiographically confirmed atraumatic vertebral fractures and 45 controls. The subjects received helical CT scans of the L1 and L2 vertebral bodies and the hip. The three-dimensional CT images were processed using specialized image analysis algorithms to extract measurements of trabecular, cortical, and integral BMD in the spine and hip. To compare the vQCT results with the most widely used clinical BMD measurement, dual X-ray absorptiometry (DXA) scans of the anteroposterior (AP) spine and proximal femur were also obtained. The difference between the subjects with vertebral fractures and the age-matched controls was computed for each BMD measure. All BMD measurements showed statistically significant differences, which ranged from 7% to 22% between subjects with fractures and controls. Although, given our small sample size, we could not detect statistically significant differences in discriminatory power between BMD techniques, integral BMD of the spine measured by vQCT and DXA tended to show stronger associations with fracture status (0.001 < p < 0.004). Measurements by QCT and DXA at the hip were also associated with vertebral fracture status, although the association of DXA BMD with fracture status was explained largely by differences in body weight between subjects with vertebral fractures and controls.