Bilateral Femoral Neck Insufficiency Fractures after Use of a Long-term Anti-resorptive Drug Therapy for Osteoporosis: A Case Report

A 78-year-old woman developed an insufficiency fracture on her right femoral neck without trauma after four years of treatment with a bisphosphonate. Her fracture was fixed by two screws and her anti-osteoporotic drug was changed from an anti-resorptive to an anabolic agent. Seven months later, however, she sustained similar insufficiency fracture on the left femoral neck and was treated with the same method. She developed right inguinal pain again approximately eight months after her right side operation. The results of imaging tests revealed that her insufficiency fracture was converted to complete fracture, and that the fracture gap had widened as well. Her right hip was revised with hemiarthroplasty. A histological exam of the fracture site revealed evidence of decreased bone healing. Long-term administration of anti-resorptive drug prevents bone healing and remodeling and can result in atypical fractures of the femoral neck. Osteosynthesis was difficult to accomplish despite the application of proactive fixation. Therefore, more rigid fixation and careful postoperative treatment should be considered.