Contralateral hip fractures and other osteoporosis-related fractures in hip fracture patients: incidence and risk factors. An observational cohort study of 1,229 patients Anne J. H. VochtelooBoudewijn L. S. Borger van der BurgMaarten A. Roling • Diederik H. van LeeuwenPeter van den BergArthur H. P. NiggebruggeMark R. de Vries • Wim E. TuinebreijerRolf M. BloemRob G. H. H. NelissenPeter Pilot

Purpose To report risk factors, 1-year and overall risk for a contralateral hip and other osteoporosis-related fractures in a hip fracture population. Methods An observational study on 1,229 consecutive patients of 50 years and older, who sustained a hip fracture between January 2005 and June 2009. Fractures were scored retrospectively for 2005–2008 and prospectively for 2008–2009. Rates of a contralateral hip and other osteoporosis-related fractures were compared between patients with and without a history of a fracture. Previous fractures, gender, age and ASA classification were analysed as possible risk factors. Results The absolute risk for a contralateral hip fracture was 13.8 %, for one or more osteoporosis-related fracture(s) 28.6 %. First-, second- and third-year risk for a second hip fracture was 2, 1 and 0 %. Median (IQR) interval between both hip fractures was 18.5 (26.6) months. One-year incidence of other fractures was 6 %. Only age was a risk factor for a contralateral hip fracture, hazard ratio (HR) 1.02 (1.006–1.042, p = 0.008). Patients with a history of a fracture (33.1 %) did not have a higher incidence of fractures during follow-up (16.7 %) than patients without fractures in their history (14 %). HR for a contralateral hip fracture for the fracture versus the non-fracture group was 1.29 (0.75–2.23, p = 0.360). Conclusion The absolute risk of a contralateral hip fracture after a hip fracture is 13.8 %, the 1-year risk was 2 %, with a short interval between the 2 hip fractures. Age was a risk factor for sustaining a contralateral hip fracture; a fracture in history was not.