Correlation of Bone Density Values of Quantitative Computed Tomography and Hounsfield Units Measured in Native Computed Tomography in 902 Vertebral Bodies

Due to the increasing age of patients, the evaluation of bone density is crucial, especially in preparation for spinal surgery. The aim of this study was to determine bone density using a computed tomography (CT) and to correlate Hounsfield units (HU) with bone density values of a quantitative computed tomography (QCT). The study is a monocentric, retrospective data analysis. We examined 902 vertebral bodies from a total of 369 patients who received a CT of the thoracolumbar spine in the period from 2015 to 2019 and compared the HU with values of a QCT. A general equation for calculation the QCT values was established. We found a significant correlation between the Hounsfield units and the corresponding QCT-values (r = 0.944, P < 0.001). We also demonstrated that the calculated QCT values are independent of patient sex (P < 0.942). Furthermore, we could not demonstrate differences in the correlation of the 3 measured levels (axial, sagittal, and coronary) to the QCT values. The QCT-values can be calculated on the basis of a native CT of the lumbar spine using the equation: QCT = 17.8 + 0.7 × HU. The equation allows calculating bone density values without the need for an additional QCT and without further radiation exposure or costs. With this measuring method it is possible to obtain additional information from a computed tomography.