Quantitative CT assessment of the lumbar spine and radius in patients with osteoporosis.

OBJECTIVE: We undertook this study to quantify the relationship between bone mineral assessments of the lumbar spine using quantitative CT (QCT) and of the radius using peripheral QCT (pQCT) and to test the sensitivity of both techniques in detecting changes in bone mass that are related to age and osteoporosis. SUBJECTS AND METHODS: Forty-two healthy premenopausal, 38 healthy postmenopausal, and 97 osteoporotic postmenopausal women were examined with pQCT of the distal radius and with QCT of the lumbar spine (L1-L4). The bone mineral density (BMD), bone mineral content (BMC), and a cross-sectional area of cortical bone were assessed at the distal radius. The BMD of trabecular and total bone and the BMC of total bone were assessed at the midvertebral bodies of the lumbar spine. RESULTS: In the healthy women, correlations of radial BMD with spinal trabecular and total BMD were modest (r = .39 and r = .49, respectively) but were higher for total BMC (r = .79). All correlations in osteoporotic women (r = .19 for trabecular BMD, r = .31 for total BMD, and r = .47 for total BMC) were lower than those in healthy women. For measurement of spinal bone mass in healthy women, trabecular BMD showed a higher correlation with age (r = .81) and a larger relative annual decrease (1.2%) than did total BMD (r = .75, .78%) or total BMC (r = .54, .55%). At the radius, the highest correlations with age were found for total BMC (r = .57, .53%), cortical area (r - .52, .67%), and cortical BMC (r = .48, .78%). Age-adjusted odds ratios for prevalent vertebral fractures were highest for total (4.5) and trabecular (4.4) spinal BMD. For radial measurements, odds ratios were highest for both total BMD (2.3) and cortical area (2.3). CONCLUSION: QCT of spinal trabecular bone showed the strongest capability for assessment of age-related bone loss and for discrimination of osteoporotic vertebral fractures. In comparison, pQCT of radial trabecular bone showed the weakest capability for these applications, and pQCT of radial cortical or total bone showed intermediate capability.