Flattening of sagittal spinal curvature as a predictor of vertebral fracture

Summary In a 12-year prospective study of 100 adult volunteers, incident vertebral fractures were analyzed for potential predictors. Decreased sagittal spinal curvature and pre-existing fractures were identified as independent predictors. The risk of vertebral fracture increased to 8.6-fold with a 1 SD decrease in both thoracic and lumbar curves. Introduction Physiological spinal curvature acts as a shock absorber: however, it has not been demonstrated whether reduced spinal curvature is a risk of vertebral fracture. The aim of this prospective study is to assess the relationship between the extent of sagittal spinal curvature and incidence of vertebral fractures. Methods One hundred community-based volunteers aged 50+ years were followed radiologically for at least 10 years. Entire spine radiograms of volunteers in erect position were used for evaluating sagittal spinal curvatures, grade of osteoporosis, and incident vertebral fractures. Results Mean baseline age was 61.9 years and mean follow-up period was 12.0 years. In multivariate analysis, preexisting vertebral fracture (relative risk [RR] 3.70, 95% confidence interval [CI] 1.22-11.20), and a decrease in either thoracic or lumbar curvature by 1-SD (RR 3.06, 95% CI 1.04-9.00) were independent predictors. The fracture risk even increased in the presence of a 1-SD decrease in both thoracic and lumbar curvature (RR 8.64, 95% CI 1.39-53.78). Conclusions Reduction of physiological curvatures in both thoracic and lumbar spine led to the increased risk of vertebral fracture by more than eightfold. The importance of evaluating sagittal spinal alignment should be emphasized, because it might indicate the risk of the first vertebral fracture, which is another strong predictor of subsequent fractures.