Osteoporosis is a disease characterized by increased bone fragility and deteriorating bone micro-architecture. The main consequence of osteoporosis is low-trauma fractures, most often of the hip, spine and wrist. Recently, another type of low-trauma fracture, atypical femur fractures (AFFs), have received much attention. Little is known of the cause of these debilitating fractures; however, they have been associated with long term bisphosphonate use. What we currently know about AFFs is based on case reports or small case series, or studies using administrative databases or secondary analyses of bisphosphonate trials. While these reports provide some preliminary information on the relationship between long term bisphosphonate exposure and AFFs, detailed clinical data are absent. As we have established a network of specialists across southern Ontario our group is in a position to collect meaningful information on a larger group of patients who have experienced these debilitating fractures into a centralized AFF registry.

Inclusion Criteria:

• Patients over the age of 20;
• Patients who have experienced an incomplete AFF that satisfies the diagnostic criteria as set forth by the American Society of Bone and mineral Research (ASBMR) International Task Force on AFFs or a low (or no) trauma fracture that mimics the features described above at other sites.

Exclusion Criteria:

• Peri-prosthetic fractures;
• High trauma fractures;
• Pathological fractures secondary to metastases or metabolic bone diseases other than osteoporosis.

primary or tertiary care clinic patients who have experienced an atypical fracture at any point in the past will be eligible for this observational study. Low trauma fractures are defined as fractures sustained with minimal force, such as a fall from standing height.