Bisphosphonates are recommended as first-line agents to reduce fracture risk in patients with osteoporosis and have in general an excellent safety profile. However, recent reports have noted that prolonged use of bisphosphonates may be associated with rare but serious adverse effects, namely atypical femur fractures (AFF), an atraumatic subset of subtrochanteric and diaphyseal fractures.

The overarching aim of this project is to contribute to the characterization of clinical, biomechanical, radiological and genetic predictors of AFF, associated or not with bisphosphonate and-or denosumab therapy. AFF arise on the lateral (external) aspect of the subtrochanteric and diaphyseal regions of the femur, regions subjected to high mechanical loads. Because of this unique distribution, the investigators hypothesis is that patients with AFF demonstrate specific geometrical variations of their femur whereby baseline tensile forces applied to the lateral cortex are higher and might favour the appearance of these rare stress fractures. Measurements to investigate these geometric variations with be calculated from 3D images reconstructed using scans procured using the EOS® low irradiation 2D-3D X-Ray scanner.

Inclusion Criteria:

• age 45 years and older
• men and women from Quebec who sustain (or have sustained) an AFF (complete or incomplete), as defined by the American Society of Bone and mineral Research (ASBMR) International Task Force on AFFs (Shane E et al J Bone Miner Res 2014;29:1-24)

Exclusion Criteria:

• inability to consent
• disorders of bone metabolism other than osteoporosis
• active cancer
• life expectancy less than 12 months.

Patients who have sustained an AFF.