Five-Year CT Follow-Up of Vertebral Fracture Risk Using Opportunistic Osteoporosis Screening

Primary objective: To assess the predictive performance of opportunistic volumetric bone mineral density (vBMD) from routine thoracoabdominal CT scans for incident vertebral fractures over 5 years or longer. Secondary objectives: * To compare the performance of vBMD to predict incident vertebral fractures with other predictors, including demographic and clinical risk factors, FRAX algorithm scores for 5-year risk of major osteoporotic fractures (MOF), prevalent vertebral fractures, and prevalent clinical fractures, as well as combinations of these predictors. * To stratify the analyses based on age decades and sex. * To compare the predictive performance between CT scans with and without administration of i.v. contrast medium. * To compare the predictive performance of vBMD (using asynchronous calibration) with Hounsfield units * To describe the prevalence and incidence (in fractures per person-years) of the study population * Assessment of the impact of a preventive treatment of patients at high risk of fracture in terms of the number of avoided fractures (simulation study)