Abdominal aortic calcification as an opportunistic marker of reduced CT-derived vertebral bone density in osteoporotic vertebral fractures.

BACKGROUND: Osteoporotic vertebral fractures (OVFs) frequently occur in patients without osteoporotic bone mineral density (BMD) on dual-energy X-ray absorptiometry (DXA), highlighting limitations of densitometry in capturing skeletal fragility. Abdominal aortic calcification (AAC) reflects cumulative cardiometabolic burden and may serve as a marker of impaired bone quality. This study evaluated the association between AAC and CT-derived vertebral bone density in patients with OVFs. METHODS: In this retrospective cohort study, 172 patients with OVFs (median age 79 years, 72.7% female) underwent DXA, CT-based Hounsfield Unit (HU) assessment, and lateral lumbar radiography. AAC was quantified using the Kauppila 24-point score. Associations between AAC and bone density parameters were assessed using correlation and multivariable linear regression adjusted for age and sex. Sensitivity analyses included severe AAC (≥16) and low bone quality (HU ≤ 90). RESULTS: AAC was inversely associated with HU in unadjusted analyses (r = -0.19, p = 0.032), with a stepwise decline across AAC categories (p = 0.038). This association was attenuated after adjustment (β = -0.68, 95% CI -1.55 to 0.20, p = 0.127), while age remained independently associated with lower HU (p = 0.030). No association was observed between AAC and DXA T-scores. Sensitivity analyses demonstrated a consistent but non-significant inverse relationship. CONCLUSION: AAC demonstrates a consistent inverse relationship with CT-derived vertebral bone density in OVF patients; however, this association is largely driven by age. These findings support AAC as an opportunistic imaging marker of skeletal fragility in older adults rather than an independent determinant of bone density.