Radiation-induced insufficiency fracture of the femur 18 years after radiation therapy

Advances in oncologic treatment have improved survival rates, allowing late effects of radiotherapy to become more prevalent. Our patient, an 82-year-old woman with a remote history of right thigh basal cell carcinoma treated with resection and radiation therapy 18 years prior, presented with severe right thigh pain and inability to bear weight as she had suffered a femur fracture after a fall from standing. Initial imaging was suspicious for pathologic fracture secondary to malignancy due to imaging findings and because radiation-induced fractures have rarely been reported beyond 44 months from treatment. However, upon further imaging, evidence pointed to radiation-induced osteonecrosis as the mechanism for her insufficiency fracture. This case highlights the permanent deleterious effects of radiation therapy on bone, and the prudence of considering radiation-induced osteonecrosis as a mechanism of injury in low-energy trauma even long after radiation therapy. In addition, the case serves to review the natural history of irradiated bone injury and pertinent imaging findings.