Incidence of stress fractures of the femoral shaft in women treated with bisphosphonate.
BACKGROUND
Recent case reports have identified an association between long-term bisphosphonate treatment and stress fractures of the femoral shaft. The risk of such fractures in bisphosphonate users has not been determined.


METHODS
We identified women over 55 years of age with the specific fracture pattern by searching the operation registry of the hospitals in 2 healthcare districts. Prevalence of bisphosphonate treatment was provided by a Swedish national registry covering all drugs delivered to all individuals since 2005.


RESULTS
The number of women on bisphosphonate treatment was 3,087. Of these, 5 had femoral stress fractures. They had been taking bisphosphonates for 3.5 to 8.5 years. The incidence density for a patient on bisphosphonate was 1/1,000 per year (95% CI: 0.3-2). In the remaining 88,869 women who were not taking bisphosphonates, there were 3 stress fractures. Thus, their risk (without correction for inhomogeneity in age distribution) was 46 times less (95% CI: 11-200).


CONCLUSIONS
These results are rough estimations based on a comparatively small material. Still, a treatment-associated incidence density of 1/1,000 is acceptable, considering that bisphosphonate treatment is likely to reduce the incidence density of any fracture by 15/1,000 according to a large randomized trial (Black et al. 1996).
Schilcher
Jörg
J
Department of Orthopedics, AIM/IKE, Faculty of Health Science, Linköping University, Linköping, Sweden.
Aspenberg
Per
P
D000368:Aged; D050071:Bone Density Conservation Agents / Q000008:administration & dosage* / Q000009:adverse effects; D004164:Diphosphonates / Q000008:administration & dosage* / Q000009:adverse effects; D005260:Female; D005264:Femoral Fractures / Q000139:chemically induced / Q000000981:diagnostic imaging / Q000453:epidemiology*; D015775:Fractures, Stress / Q000139:chemically induced / Q000000981:diagnostic imaging / Q000453:epidemiology*; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D015995:Prevalence; D011859:Radiography; D012042:Registries; D012307:Risk Factors; D013548:Sweden / Q000453:epidemiology; D013997:Time Factors
D050071:Bone Density Conservation Agents; D004164:Diphosphonates