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Clinically Silent Lumbar Spine Osteopenic Changes in the Middle-Aged and Elderly Population: Usefulness of Standard Abdominal Computed Tomography Scans
Purpose: To evaluate whether retrospective analysis of standard abdominal computed tomography (CT) scans in middle-aged and elderly patients can provide reliable information regarding decreases in vertebral trabecular bone mineral density (BMD), possible vertebral body fracture, and stage of its severity.
Methods and Materials: A total of 119 patients (7 men, 112 women) aged 50 to 83 years (mean: 64.6; 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 and 2019 were included in this 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 levels L1 to L4. Circular region of interest, 20 mm diameter, was drawn in the axial plane in the middle of the vertebral body excluding cortical margins. The DXA T-score of the lumbar spine served as the reference standard. Linear regression analysis and independent sample Kruskal-Wallis tests were applied to the obtained data.
Results: Using abdominal CT, we found that 21 patients had 1 mild, 8 moderate, and 12 severe lumbar vertebral body fractures at L1–L4. Of these patients, DXA showed vertebral height loss in just three patients: one moderate and two severe fracture cases. DXA sensitivity for vertebral fracture assessment compared with CT was < 0.15. Linear regression with moderate correlation was found between mean lumbar vertebral body CT Hounsfield (HU) measurements and mean DXA BMD estimates (correlation coefficient [r] = 0.63). However, it was different in L1, L2, L3, and L4 vertebrae: 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 measurements (except for the L1 and L3 pair). However, DXA BMD measurements were significantly different (except for the L3 and L4 pair). CT values for normal bone density (DXA T-score ≥ 1.0) was ≥ 140 HU [95% confidence interval]). A 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 < 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.
Conclusion: Retrospective analysis of standard abdominal CT scans provides useful and reliable information regarding vertebral bone density and allows differentiating between 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 < 140 HU have to undergo an additional radiologic examination (quantitative CT) to evaluate the severity of decreased bone density and potential vertebroplasty planning.
Article published online:
17 December 2020
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