Bisphosphonate-Induced Atypical Femoral Fractures in Pediatric Patients With Lipoprotein Receptor-Related Protein 5...

Atypical femoral fractures (AFFs) are rare complications in children receiving bisphosphonate therapy for bone disorders. Early-onset osteoporosis in this population is often linked to monogenic bone diseases caused by genetic mutations. This study aims to highlight the risk of AFFs associated with bisphosphonate therapy in pediatrics and review the treatment approaches for these fractures. We report two cases of AFFs in nine-year-old identical twins with early-onset osteoporosis secondary to a lipoprotein receptor-related protein 5 (LRP5) gene mutation. Both had been receiving long-term zoledronic acid therapy. Each twin sustained a low-energy, left-side, transverse fracture of the proximal femoral shaft within a span of nine days. Radiological imaging revealed evidence of an impending fracture on the contralateral femur in both cases. The fractures were managed with intramedullary nailing using the Orthopediatrics Simple Locking IntraMedullary (SLIM^TM, OrthoPediatrics Corp., Warsaw, IN) nail system, augmented with a lateral plate and screws. Sequential prophylactic fixation of the contralateral side was also performed using the same nail system. Radiographic evaluation at six weeks showed progressive callus formation, with complete union by 12 weeks. Clinically, both patients achieved full weight-bearing capacity without pain and returned to age-appropriate daily activities. No surgical complications, implant failures, or recurrent fractures were observed during follow-up. The described fixation techniques for the AFFs in pediatric patients proved to have a good functional outcome with full healing. Further studies are required to determine whether the risk of AFFs is primarily influenced by the underlying monogenic bone disease, the long-term use of bisphosphonates, the dosage regimens involved, or a combination of these factors. Contralateral limb imaging is recommended to identify potential impending fractures and ensure appropriate management.