Normative Vertebral Hounsfield Unit Values and Correlation with Bone Mineral Density

Background: We hypothesized that vertebral bone mineral density as measured in Hounsfield units (HU) by computed tomography (CT) can correlate with values obtained by dual x-ray absorptiometry (DXA). Our study aimed to report such a correlation along with the normative HU values within a large, heterogeneous population. Methods: We identified 2,020 trauma patients with a CT scan encompassing any part of their thoracic or lumbar spine. Mean HU values within each vertebral body were reported with respect to vertebral level, sex, and age. Using linear regression analysis, our data were also compared to DXA results in patients having both CT and DXA scans. Results: Analyses of CT scans yielded 28,083 unique vertebrae (18,489 male and 9,594 female) for which HU values were obtained. There were significant correlations between lumbar vertebral body HU and both DXA bone mineral density estimates (R2 = 0.50) and T-scores (p<0.001 and p<0.01, respectively). Using DXA T-scores as the reference standard, the sensitivity, specificity, and positive and negative predictive values of CT HU were 0.93, 0.75, 0.74 and 0.94, respectively. Conclusion: CT can be used to measure vertebral bone mineral density and may aid in the diagnosis and management of osteoporosis.