Atypical Femoral Fractures in Adult Patients with Classical Osteogenesis Imperfecta.

Atypical femoral fractures (AFF) are rare fractures with characteristic radiographic features, most commonly associated with long-term bisphosphonate use. Their occurrence in patients with osteogenesis imperfecta (OI), a hereditary bone disease leading to bone fragility, is not well understood. In this study, 138 adults with genetically confirmed classical OI were screened for AFF. Five patients with AFF were identified and compared to an age- and treatment-matched adult OI cohort without AFF (n = 23). Demographical parameters, biochemical markers, bone mineral density (DXA), bone microarchitecture (HR-pQCT), and radiographs were analyzed. In addition, antiresorptive therapy and the duration of treatment were determined and compared. In the screened OI cohort, AFF prevalence was 3.6%. No significant differences were observed between groups regarding age, weight, height, BMI, fracture history, bone mineral density, or antiresorptive therapy exposure and duration. HR-pQCT showed no significant microarchitectural differences, although a trend toward higher cortical thickness was noted in AFF patients. AFF are a rare complication in adults with classical OI and appear to be multifactorial in origin. Our findings suggest that AFF are not exclusively related to antiresorptive therapy but may be influenced by disease-specific factors, particularly the underlying collagen defect, femoral deformities and altered biomechanics. Individualized management strategies are essential, and further studies are needed to clarify underlying mechanisms and best treatment options.