Our purpose was to characterize the risks of
osteoporosis-related
subtrochanteric fractures in
bisphosphonate-naive individuals. Baseline characteristics of patients enrolled in the HORIZON-Recurrent Fracture Trial with a study-qualifying hip fracture were examined, comparing those who sustained incident
subtrochanteric fractures with those sustaining other
hip fractures. Subjects were
bisphosphonate-naive or had a
bisphosphonate washout period of 6-24 months and subsequently received an annual infusion of
zoledronic acid 5 mg or placebo after low-
trauma hip-fracture repair. In total, 2,127 men and women were included. Of the qualifying
hip fractures, 5.2% were subtrochanteric, 54.8% femoral neck, 33.0% intertrochanteric, and 7.1% other (generally complex fractures of mixed type). Significant baseline (pre-hip fracture) differences were seen between index hip-fracture types, with the percentage of patients with extreme mobility problems being twofold higher in patients with index subtrochanteric fracture (9.9%) compared to other patients. The distribution of hip-fracture types was similar between the treatment groups at baseline. No patients with index
subtrochanteric fractures and six patients with other qualifying
hip fractures reported prior
bisphosphonate use. Only one further subtrochanteric fracture occurred in each treatment group over an average 2-year patient follow-up.
Subtrochanteric fractures are not uncommon in
bisphosphonate-naive patients. Extreme difficulties with mobility may be a unique risk factor predisposing to development of incident
subtrochanteric fractures rather than other types of hip fracture. In patients with recent hip fracture who received
zoledronic acid therapy, the incidence of new
subtrochanteric fractures was too small to draw any meaningful conclusions.