Prevalent vertebral fractures on chest CT: higher risk for future hip fracture

Subclinical or undiagnosed vertebral fractures on routine chest computed tomography (CT) may be useful for detecting patients at increased risk of future hip fractures who might benefit from preventive interventions. We investigated whether prevalent vertebral fractures on routine chest CT are associated with future hip fractures. From a source population of 5679 patients ≥40 years old undergoing chest CT in one of three Dutch hospitals between 2002 and 2005, patients hospitalized for hip fractures (n = 149) during a median follow-up of 4.4 years were identified. Following a case-cohort design, a random sample of 576 patients was drawn from the source population and added to the cases. In this group, the presence and severity of vertebral fractures was determined using semiquantitative vertebral fracture assessment and multivariate case-cohort appropriate Cox modeling. We found that cases were older (69 versus 63 years) and more often female (48% versus 38%) than the source population. Compared with those with no fracture, patients with any vertebral fracture had triple the risk of future hip fracture (age- and gender-adjusted hazard ratio [HR] = 3.1, 95% confidence interval [CI] 2.1-4.7). This HR rose to 3.8 (CI 2.6-5.6) if mild fractures were discounted. Future fracture risk increased significantly with increasing severity of vertebral fracture status: from mild (HR = 2.4, CI 1.5-3.7) and moderate (HR = 4.8, CI 2.5-9.2) to severe (HR = 6.7, CI 2.9-15.5). The same was true for having higher cumulative fracture grades: 1 to 3 (HR = 2.7, CI 1.8-4.1), 4 to 6 (HR = 4.8, CI 2.2-10.5), or ≥7 (HR = 11.2, CI 3.7-34.6). In conclusion, prevalent vertebral fractures on routine clinical chest CT are associated with future hip fracture risk.