Avascular necrosis of the femoral head following an occult femoral neck stress fracture

Abstract

Introduction. Osteonecrosis of the femoral head (ONFH) is an intractable disease that causes progressive femoral head collapse, severe pain, and gait disturbance. We report a case of avascular necrosis of the femoral head following an occult femoral neck stress fracture, which shows that early diagnosis and treatment are very important. Case report. A 55-year-old woman presented to our department with a chief complaint of low back pain that radiated into the left anterolateral thigh for 2 months Her left anterolateral thigh became progressively more painful over a period of about 2 weeks. No abnormal findings indicative of ONFH or an occult fracture of the femoral neck were detected by X-ray or computed tomography (CT), but an occult insufficiency fracture of the left femoral neck was identified on magnetic resonance imaging (MRI). The diagnosis of femoral neck stress fracture was delayed, resulting in femoral head necrosis. The fracture was treated with total hip arthroplasty and the resected femoral head was subjected to histopathology. Based on the histopathological findings, the final diagnosis of this case was ONFH with an occult fracture of the left femoral neck. Clinical symptoms were relieved postoperatively. Conclusion. In patients presenting with a suspected stress fracture of the femoral neck, early MRI examination is recommended to avoid femoral head necrosis due to a delayed diagnosis.