Trends in the incidence of atypical femoral fractures and bisphosphonate therapy

Purpose. To report the trends in the incidence of typical and atypical femoral fractures (AFF) in patients aged >50 years from 2009 to 2014 and in the prescription of bisphosphonates for osteoporosis from 2001 to 2013 in Australia. Methods. 175 patients aged >50 years presenting to our hospital with an AO type 32 femoral shaft fracture between October 2009 and October 2014 were identified using a trauma database. Of them, 21 male and 110 female patients with a mean age of 75 years were reviewed. Radiographs were reviewed by 2 investigators blinded to the use of bisphosphonates. The femoral shaft fractures were classified as typical or atypical using the American Society of Bone and Mineral Research definition, and their annual incidence was compared. The trend and number of prescriptions for various bisphosphonates in Australia was determined using the Pharmaceutical Benefits Scheme statistics from 2001 to 2013. Results. Of the 131 femoral shaft fractures, 65 were typical and 66 were atypical subtrochanteric (n=19) or diaphyseal (n=47) fractures that were complete (n=60) or incomplete (n=6). Four patients had sequential bilateral AFF. The 66 AFFs accounted for 5% of hip and shaft fractures. Women accounted for 80% of all femoral shaft fractures and 95% of AFF. The proportion of AFF was higher in women than men (63/110 vs. 3/21, relative risk=3.95, 95% CI=1.3711.39, p=0.0006). The mean length of hospital stay was 9.7 days shorter in the AFF patients (14.1 vs. 23.8 days, 95% CI=2.6-16.8 days, p=0.008). Patients with AFF were 8 years younger than those with proximal femoral fracture (73 vs. 81 years, p<0.0001). There was no trend in the annual incidence or proportion of AFF from 2009 to 2014 (p=0.70). The bisphosphonate usage was highest in 2007 with 260 000 yearly patient treatments and had declined by 30% by the end of 2013. Conclusion. AFF accounted for half of all femoral shaft fractures in patients aged >50 years. Women accounted for 80% of all femoral shaft fractures and 95% of AFF. The incidence of AFF was no longer increasing possibly related to decreased prescription of bisphosphonates in preceding years.