Earlier this year, an update to the ASBMR Task Force on Atypical Femoral Fractures (AFF) seminal 2010 report was published on JBMR® Online. Task Force Co-Chairs Elizabeth Shane, M.D., and David Burr, Ph.D. discuss the new report and the latest AFF evidence.
What is the significance of this updated Task Force Report?
David Burr: “With the newer data, it is now much clearer that AFF are a form of stress or insufficiency fracture. In addition, the evidence for an association with long-term bisphosphonate therapy is considerably stronger than it was at the time of the 2010 report, and based on several different types of studies, including a meta-analysis. The new report also updates what we know about the pathophysiology of the fractures.”
How does the latest report build on the evidence from the initial 2010 task force report?
Elizabeth Shane: “The initial report introduced the major and minor features of AFF. In the updated report, the major and minor features have been revised and refined to be consistent with new data, and to distinguish AFF from ordinary osteoporotic fractures of the femoral diaphysis. The periosteal stress reaction at the fracture site, which is thought to represent callus formation and is sometimes referred to as “beaking,” was changed from a minor to a major feature.”
David Burr: “The description of certain major features has also been expanded. For example, the new report emphasizes that, at their point of initiation in the lateral femoral cortex, AFF are transverse to the longitudinal axis of the femur, but may become oblique as they extend across the femoral shaft. In addition, the requirement that AFF fractures be non-comminuted was relaxed to include minor degrees of comminution.”
How do you hope the report affects future research and clinical management of osteoporosis?
David Burr: “AFF have now been identified as stress or insufficiency fractures, with a strong association with prolonged treatment with anti-remodeling agents, particularly bisphosphonates. They have also been reported in patients treated with denosumab. This observation is key to developing animal models. The updated report also identifies several aspects of bone quality [e.g. Advanced Glycation Endproducts (AGE) and microdamage accumulation, and other potential risk factors such as ethnicity, lower limb geometry] that should be studied as possible contributing factors to the fracture. The revised, more precise major features will help us to gather more precise estimates of both the incidence and prevalence of AFF.”
Elizabeth Shane: “It is now clearer that prolonged treatment with anti-remodeling agents contributes to the development of AFF. Even so, AFF are relatively uncommon, and the benefits of anti-remodeling agents for prevention of common osteoporotic fractures outweigh the relatively small risk of AFF. However, recognition of these risks has prompted physicians to target therapy towards patients at high risk of fracture and to consider the optimal duration of therapy with anti-remodeling agents. Since the initial task force report, several studies have reported on the use of teriparatide for AFF. To date, the data are conflicting and additional studies are necessary to assess the efficacy of teriparatide in accelerating healing of both complete and incomplete AFF.”
The full task force report is available as an Accepted Article on JBMR® Online.