Purpose
The purpose of this study was to evaluate whether retrospective analysis of standard abdominal CT scans in middle age and elderly patients can provide reliable information regarding vertebral trabecular bone density decrease, possible vertebral body fracture and stage of its severity.
Methods and materials
119 patients (7 men, 112 women) at age 50 years (y.) to 83 y. (mean age 64.6 y., standard deviation [SD]=9.1), who underwent abdominal CT examination as well as a lumbar spine dual-energy X-Ray absorptiometry (DXA) test within 90 days at the Riga East Clinical University Hospital between 2012 – 2019 were included in retrospective study. The exclusion criteria were lumbar spine implants, spinal inflammation, and malignancies.
Lumbar spine trabecular bone radiodensity values were measured in CT scans from L1 to L4 levels. Circular ROI, 20 mm diameter, was drawn in axial plane, in the middle of vertebral body excluding cortical margins.
DXA T-score of the lumbar spine served as the reference standard. Linear regression analysis and independent samples Kruskal-Wallis tests were applied to the obtained data.
Results
Using abdominal CT was found that 11 patients had 1 mild, 8 moderate and 12 severe lumbar vertebral body fractures at the level L1-L4, out of these patients DXA showed vertebral height loss just in 3 patients: 1 moderate and 2 severe fracture cases. DXA sensitivity for vertebral fracture assessment compared to CT was less than 0.15.
Linear regression with moderate correlation was found between mean lumbar vertebral body CT HU measurements and mean DXA BMD estimates (correlation coefficient [r]=0.63), however it was different in L1, L2, L3 and L4 vertebrae as 0.69, 0.64, 0.58 and 0.50, respectively. Pairwise comparison analysis for L1-L4 vertebrae showed no significant difference (p<0.05) in CT HU measures (except for L1 and L3 pair), however DXA BMD measures were significantly different (except for L3 and L4 pair). CT values for normal bone density (DXA T-score≥-1.0) was of 140 HU and above (confidence interval [CI]=95%). Statistically significant difference (p<0.05) was not found between osteopenia (DXA T-score between -1.0 and -2.5) and osteoporosis (DXA T-Score≤-2.5) for CT values below 140 HU. The sensitivity, specificity, positive predictive values, negative predictive values, and accuracy of CT HU for diagnosing low bone density were 0.89, 0.69, 0.85, 0.76 and 0.82, respectively.
Conclusions
Standard abdominal CT scans retrospective analysis provides useful and reliable information regarding vertebral bone density and allows differentiating normal and low bone density. This method, avoiding additional irradiation and costs, can serve as the first screening method for patients with clinically silent spinal osteopenia. Patients with lumbar spine trabecular bone radiodensity below 140 HU have to undergo additional radiological examination (quantitative CT) to evaluate severity of bone density decrease and potential vertebroplasty planning.

Clinically silent lumbar spine osteopenic changes in the middle age and elderly population: usefulness of standard abdominal computed tomography scans