Differences in lumbar spine bone mineral density measured by quantitative computed tomography and dual-energy X-ray absorptiometry: an age- and sex-specific analysis

BACKGROUND: Dual-energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT) are the usual methods for evaluating bone mineral density in patients with spinal osteoporosis. However, the influence of sex and age remains unexplored. The study aims to reveal the differences in age- and sex-specific bone mineral density (BMD) evaluations in patients undergoing spinal surgery. METHODS: A total of 1144 elderly patients underwent both QCT and DXA from March 2021 to November 2024 were enrolled. A paired chi-square test was used to compare the osteoporosis detection rates between QCT and DXA. Scatter plots with DXA and QCT were constructed to test whether the BMD distribution difference changed with patient sex and age. RESULTS: Of the 1144 patients, 56.5% were diagnosed as osteoporosis via QCT, whereas 42.3% were diagnosed as osteoporosis via DXA. In total, 408 (35.7%) patients met the osteoporosis criteria on both QCT and DXA. Among the other 314 patients with diagnostic discordance, 238 (20.7%) met the QCT-based osteoporosis criteria but were diagnosed as osteopenic or normal via DXA criteria; 76 (6.7%) were diagnosed with osteoporosis by DXA but not by QCT. QCT BMD was significantly associated with age in both females (P < 0.001) and males (P < 0.001), and this negative correlation was more obvious in females (r = -0.667). Notably, DXA T scores were significantly (P < 0.001) and negatively related to age (r = -0.353) in females but not in males (r = -0.017, P = 0.301). CONCLUSIONS: Among elderly patients scheduled for spinal surgery, QCT demonstrates a higher detection rate of osteoporosis in males compared to DXA. Regarding BMD evaluation in females, much consideration should be given to sex- and age-specific differences between DXA and QCT results.