Atypical femoral fractures in a Mexican cohort of children and adolescents with osteogenesis imperfecta. Analysis of trajectories.

INTRODUCTION: osteogenesis imperfecta (OI) is a rare inherited bone disorder resulting from defects in type I collagen synthesis or structure. It is characterized by increased bone fragility, recurrent fractures, and early-onset hearing loss. Management requires a multidisciplinary approach aimed at reducing fracture incidence, enhancing mobility, and promoting functional independence. Since 1998, bisphosphonates (BPs) have been used as compassionate therapy in OI. OBJECTIVE: to characterize children with osteogenesis imperfecta (OI) and report the incidence of atypical femoral fractures (AFFs) in relation to the duration of zoledronic acid treatment. MATERIAL AND METHODS: a single group ambispective cohort study of pediatric patients diagnosed with osteogenesis imperfecta according to the Sillence criteria and treated with zoledronic acid (0.1 mg/kg/year); the retrospective period spanned from January 2008 to July 2017, while the prospective period extended from October 2017 to March 2024. RESULTS: a total of 68 patients were included, with 24 fractures identified in 21 patients (31%). Fractures were more frequent in males (67%), adolescents (76%) and those receiving continuous treatment (76%). The duration of treatment before developing an AFF was also shorter in males (69 months) compared to females (77 months). Cox regression analysis showed that male patients with OI had a hazard ratio (HR) 3.13 (95% CI 1.18-8.26, p = 0.021) indicating a significantly higher risk of developing an AFF compared to female patients. CONCLUSION: there may be an association between prolonged use of zoledronic acid and the occurrence of AFFs. Male and adolescents exhibited a higher risk of AFFs (HR 3.13, 95% CI 1.18-8.26) These fractures may not be limited to the femur, as other long bones could also be affected. Larger cohorts and longer follow-up periods, including control groups not exposed to zoledronic acid, are needed to establish causation.