Predictors of new and severe vertebral fractures: Results from the HoRIZoN Pivotal Fracture Trial

Summary: We examined prevalent and recent vertebral fractures in 1 year as predictors of new vertebral fractures over subsequent 2 years using data from RCT placebo patients. We found that prevalent and recent vertebral fractures strongly and independently predicted subsequent vertebral fractures including those which were severe. Introduction: While several studies have shown that prevalent vertebral fractures (pVFx) increase the risk of new vertebral fractures (VFx), the impact of recent vertebral fractures on future fractures is less studied. Methods: Data from the placebo arm of the HORIZON Pivotal Fracture Trial, an international trial of zoledronic acid in postmenopausal, osteoporotic women between 65 and 85 years, were used. We included the subset of 2677 women with annual spinal radiographs to study the impact of vertebral fractures in year 1 (Y1 VF) on those occurring in years 2 and 3 using morphometric and semiquantitative (SQ) criteria. In addition, a subset of severe VFx was defined using SQ criteria. Logistic regression examined the impact of pVFx and Y1 VF on all incident VFx and on severe incident VFx. Results: Two hundred fourty-five (9.1%) women sustained a new VFx in years 2–3. VFx risk in years 2–3 was 3.9% in those without pVFx or VFy1 and 29.8% in those with both risk factors. Both pVF and VFy1 remained independent predictors for future VF when they were both entered into a logistic regression model (odds ratio (OR) = 3.3; 95% confidence interval (CI), 2.3–4.7; OR = 3.7, 95% CI, 2.3, 5.8, respectively). ORs were similar after adjustment. Of the total number of women, 4.1% had severe VFx. PVFx and Y1 VF were also significant predictors of severe VFx; however, Y1 VF appeared more strongly predictive of severe VFx. Conclusions: Prevalent and incident vertebral fractures are highly predictive of subsequent new and severe vertebral fractures. Women with both of these risk factors are likely to benefit from anti-osteoporosis treatment.