Spontaneous bilateral femoral neck subcapital fractures in bilateral osteonecrosis of the femoral head: A case report and review of the literature

Femoral neck fracture rarely occurs during the course of osteonecrosis of the femoral head (ONFH). We report a case of spontaneous bilateral femoral neck subcapital fractures in the presence of bilateral ONFH. A 30-year-old man developed bilateral hip pain while working. Plain radiographs revealed bilateral displaced subcapital fractures of the femoral neck. Magnetic resonance imaging (MRI) scans demonstrated a typical finding of bilateral ONFH. The fractures were treated with bilateral total hip arthroplasty. He had recovered satisfactorily and could return to work without any problem. ONFH rarely causes bilateral femoral neck fractures. We performed routine laboratory blood examinations and biochemical and endocrine tests, which excluded the possibility of any underlying metabolic disorders. We also performed MRI to evaluate the severity of ONFH. Fractures occurred in the subcapital area between the interface of necrotic and regenerative bone. ONFH may suddenly deteriorate to become a femoral neck fracture without head collapse or any recognizable trauma event. Although rare, bilateral hip involvement is possible. Care should be directed to the proper diagnosis and appropriate treatment of such fractures.