Asian ethnicity is associated with atypical femur fractures in an Australian population study

Asian race, younger age, higher body mass index (BMI) and antiresorptive drugs have all been associated with atypical femur fractures (AFFs). This increased risk of AFF in Asians is important as by 2050, > 50% of hip fractures globally will occur in Asia, with an increased demand for antiresorptive drugs being likely. It is also currently unclear whether AFF risk is increased in all Asian subgroups. We therefore aimed to identify the incidence of AFFs in an Australian tertiary hospital, the contribution of ethnic origin to AFF risk, and determine other clinical risk factors for AFF. From January 1, 2009 to December 31, 2017, 97 AFFs (82 complete and 15 incomplete) occurred in 71 individuals in the overall study population of 204,358. Patients with AFF were more likely to be female (88.7% vs 69.1%, p < 0.001) and younger [median (IQR): 74(52-92) years vs 83(75-88) years, p < 0.001] than the typical femur fracture group (n = 3330). The cumulative incidence rate of AFF was 4.2 per 100,000 person-years, far lower than for any ICD-10 AM coded typical femur fracture (202.9 per 100,000 person-years). Asians were 3.4 (95%CI, 2.1-5.6) times more likely to sustain an AFF than non-Asians, the highest incidence being in those from South East Asian countries (16.6 per 100,000 person years), suggesting differences in risk between Asian countries. In the nested case-control study, bisphosphonate use was an independent association with AFF development. We conclude Asian ethnicity is an important association with AFF in this large Australian cohort.