However, Epacadostat clinical trial this terminology also requires clarification, as not all stress fractures are

atypical. Epidemiology of subtrochanteric fractures Subtrochanteric fractures are a relatively rare type of hip fracture [44–46], usually resulting from high-energy trauma, pathologic fracture or, in the elderly, low-energy injury involving osteoporotic bone. Several series report the incidence of this fracture [25–28, 30, 36, 37, 47], although the definition of the subtrochanteric site has varied. Nieves et al. reported a large, 11-year epidemiological study of fractures of the hip, subtrochanter, femoral shaft and distal femur in the US population aged ≥50 years using National ACP-196 purchase Hospital Discharge Survey data from the National Center for Health Statistics and MarketScan® (medical claims experience) data [46]. Of all femoral fractures, 3% were at the subtrochanteric region, ABT-737 in vivo 5% at the femoral shaft, 5% at the distal femur and 87% were at the proximal femur (i.e. hip). Importantly, this study classified fractures solely according to their location in the femur and did not evaluate the fracture patterns radiographically. Thus, they were not able to determine the incidence of ‘typical’ vs ‘atypical’ subtrochanteric fractures. In men and

in women, the incidence rate of each type of fracture FER remained stable over 5 years but increased exponentially with age (Fig. 1). Each fracture type was more prevalent in women than in men. Seventy-five percent of all femur fracture cases were in women. The mean age at fracture was 80 years old, and those with a subtrochanteric fracture were of a similar age to those with a hip fracture. Fig. 1 Age-specific incidence of femoral fractures according to fracture site in men (X) and women (O) aged ≥50 years (adapted from Nieves et al. [46]) Leung et al. published a retrospective analysis that aimed to document the incidence of low-trauma subtrochanteric

or femoral diaphyseal fractures in a Hong Kong hospital over a 5-year period [42]. In all, 88 cases of subtrochanteric fractures and 66 of diaphyseal fractures were identified, accounting for 3.9% and 2.9% of all recorded osteoporotic fractures, respectively. Thus, although the incidence of subtrochanteric fractures is much lower than other femoral fractures, they are not rare and account for about 3% of all femoral fractures in the elderly. If these estimates were applied to the UK, then more than 2,000 subtrochanteric fractures are expected to occur each year [48], and approximately 48,000 are expected annually worldwide [49].