Characteristics of bisphosphonate and non-bisphosphonate related atypical femoral fracture in a South East Asian population - Secondary analysis.

Introduction: Studies have found that not all atypical femoral fractures (AFF) are associated with bisphosphonate (BP) use. There are limited data on AFF in non-BP patients. In this study, we characterise factors associated with BP and non-BP related AFF and its mortality in a single centre in Singapore.

Methods: We conducted a cohort study of subjects above 50 years old admitted to Changi General Hospital (CGH), Singapore with fragility subtrochanteric and femoral fractures from 2009 to 2015. Using the ASBMR 2014 criteria fractures are classified into atypical and typical femoral fractures. CGH uses a nationalised electronic health record that allows review of information on patient's demographics, clinical history and previous investigations. Mortality was assessed as of 31st December 2019.

Results: Between 2009 and 2015, there were 3097 hip fractures, of which 393 were subtrochanteric and femoral fractures and 69 were classified as AFF by ASBMR 2014 criteria. 35 of AFF occurred in BP exposed and 34 occurred in non-BP exposed patients. There were no significant demographic differences in patients with BP and non-BP related AFF. There were also similar incidences of type 2 diabetes, rheumatoid arthritis and glucocorticoid use. Notably, there were a higher percentage of previous fragility fractures (35.3 % vs 9.4 %) in BP related AFF. Time to healing of fracture was slightly longer in BP related AFF at median (3 months vs 2 month, p = 0.02), however there were no differences in incidence of delayed healing. Mortality between BP and non-BP related AFF were similar.

Conclusion: In a South East Asian population in Singapore, 47.8 % of AFF were found to be non-BP related. We found no major demographic and clinical differences between BP and non-BP related AFF. Mortality between BP and non-BP related AFF was similar. Further studies are needed to better understand the optimal treatment of osteoporosis in AFF prone patients in the Asian population.