Mortality After Atypical Femoral Fractures: A Cohort Study

Mohammad Kharazmi, Pär Hallberg, Jörg Schilcher, Per Aspenberg, Karl Michaëlsson

Although osteoporotic fracture rates can be reduced by bisphosphonates, prolonged therapy is associated with higher risk of atypical femoral fractures. Ordinary fragility fractures are linked to high mortality rates. We aimed to determine whether atypical femoral fractures also confer excess mortality. Radiographs were reviewed for all patients ≥55 years of age who had experienced a subtrochanteric or femoral shaft fracture in Sweden in 2008-2010. The fractures were classified as either atypical or ordinary. Data on medication use, coexisting conditions, and date of death were obtained from national registers. We estimated multivariable-adjusted relative risks of death after atypical femoral fractures compared with ordinary subtrochanteric or femoral shaft fractures and calculated age- and sex-standardized mortality ratios (SMRs) for atypical and ordinary fractures compared with the population average. During a mean of 4 years of follow-up, 39 of 172 (23%) patients with an atypical fracture had died compared with 588 of 952 (62%) with an ordinary fracture, corresponding to a relative risk of 0.51 (95% CI 0.38-0.68). The lower risk was evident in both users and non-users of bisphosphonates. No patient with atypical fracture died in the first year after fracture. Individuals with an ordinary fracture had a higher mortality risk than the general population (SMR 1.82; 95% CI 1.69-1.99) but no excess risk was found in patients with atypical fracture (SMR 0.92; 95% CI 0.65-1.26). We conclude that in contrast to ordinary subtrochanteric and femoral shaft fractures, atypical femoral fractures are not associated with excess mortality. This article is protected by copyright. All rights reserved.