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Osteoporosis in men: associations between BMD and spinal fractures
In men with glucocorticoid-induced osteoporosis (GIO), bone mineral density (BMD) declines quickly at first, because of increased bone resorption, and then more slowly over a longer period due to decreased bone formation.
This study examined the association between vertebral fractures and BMD in men with GIO using dual X-ray absorptiometry (DXA) to measure areal BMD, quantitative computed tomography (QCT) or high-resolution QCT to measure cortical BMD and thickness (Ct.BMD) and trabecular BMD and thickness (Tb.BMD), and finite element analysis (FEA) to assess bone strength. These values were compared between two groups of male patients with GIO, one with vertebral fractures apparent on thoracic or lumbar spine X-rays, the other without.
After adjusting for confounding factures, Tb.BMD was the measure most closely correlated with the presence of fractures at the T12 vertebra—standardized odds ratio (sOR) 4.05 (95% CI 1.8–9.0)—and at L1–L3 (sOR 3.95 [95% CI 1.8–8.9]). This compared to sOR 2.56 (95% CI 1.29–5.07) for the most significant FEA variable. DXA measurements at the hip or spine were not significantly associated with fracture status or severity.
Editor’s comment: It is well known that fracture risk in GIO increases more rapidly than the decline of areal BMD would suggest. Intervention thresholds of between −1 and −1.5 T-score are therefore usually recommended, rather than ≤−2.5. Here, sophisticated imaging techniques demonstrate that alterations in vertebral strength and trabecular BMD are far better predictors of vertebral fractures than DXA-assessed areal BMD.
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