A Retrospective Analysis of all Atypical Femur Fractures Seen in a Large California HMO from the Years 2007 to 2009
Category: Disorders of Bone and Mineral Metabolism (Genetic, Basic, and Trans.)
Oral Presentations, Presentation Number: 1201
Session: Concurrent Oral Session 34: Osteoporosis Epidemiology: Fracture Prevention
Monday, October 18, 2010 3:15 PM - 3:30 PM, Metro Toronto Convention Centre, South Building, South Building: Hall F
Richard Dell, Kaiser, USA, Denise Greene, Kaiser, USA, * Susan Ott, University of Washington, USA, Stuart Silverman, Cedars Sinai, USA, Eric Eisemon, Maimonides Medical Center, USA, Tadashi Funahashi, Kaiser, USA, Annette Adams, Kaiser, USA
Nontraumatic fractures of the femoral diaphysis with an unusual appearance have been recently reported in patients on long term oral bisphosphonates. These case series have not been able to enumerate the population at risk and the incidence of these atypical fractures has not been defined. We therefore conducted a study in a defined population to characterize these fractures and estimate their incidence. Using electronic data sources from a large California health maintenance organization, we identified all subtrochanteric and femur shaft fractures that occurred in patients aged 45 years or older between 1/1/2007 and 12/31/2009. All fractures above the subtrochanteric femur
region and below the distal femoral flair were excluded, as were periprosthetic fractures, pathologic fractures secondary to tumor, and high energy fractures.
The HMO serves 2.6 million patients 45 years or older. Records on over 15,000 femur fractures cases were screened and over 600 radiographs were then reviewed that meet inclusion criteria. We identified those with atypical features that included lateral cortical thickening, a transverse fracture with short oblique extension medially, and flaring of the lateral cortex. For all patients with qualifying fractures, demographic, clinical, and pharmacy data were gathered. 102 patients (99 women, 3 men) had the characteristic radiographic findings. 61% of the fractures occurred in the shaft region and 39% in the subtrochanteric region. 25% of the patients had either a complete fracture or stress fractures on the contralateral femur. The average age was 72 years old (range 45 to 92). Prodromal pain was reported by 70% of the patients. Five patients had not taken a bisphosphonate and 97 patients were on oral bisphosphonates with an average duration of use of 5.5 years. There was no correlation between the duration of bisphosphonate use and the patient age. Based on the number of patients receiving oral bisphosphonate treatment in our HMO (300,000 filled at least one prescription since 2002), preliminary estimates of atypical femur fracture incidence show a progressive increase with longer duration of treatment, from 2:100,000 per year to 78:100,000 cases per year as the duration of treatment went from 2 years to 8 years of oral bisphosphonate treatment.
These preliminary incidence estimates suggest that atypical femur fractures are rare in the general population, but may be more common among patients with longer-term oral bisphosphonate use.
* Presenting Authors(s): Susan Ott, University of Washington, USA