Bilateral subchondral insufficiency fracture of the femoral head.

Subchondral insufficiency fracture of the femoral head is a rarely reported lesion, often confused with osteonecrosis, transient osteoporosis of the hip, or rapidly destructive coxarthrosis. However, almost all the previous reports about this lesion have documented unilateral cases. We report the clinical and histological features of bilateral subchondral insufficiency fracture of the femoral head in a 68-year-old woman. She reported a sudden pain in her left hip without apparent trauma. An anteroposterior radiograph 2 weeks after the onset of pain in the left hip shows a subchondral collapse of the femoral head. The entire femoral head was depicted as a low intensity area on a T1-weighted image, and there was a subchondral linear pattern of low signal intensity with a convex shape to the articular surface. On T2-weighted image, the entire femoral head was depicted as a high intensity area, and on T1-weighted image, a linear low signal intensity pattern was noted. The patient underwent hemiarthroplasty. Cross-section of the femoral head showed a fracture line identified in the subchondral area. Although the patient's postoperative course was favorable, she had idiopathic pain in the right hip. A lateral radiograph 3 weeks after the onset of pain in the right hip shows irregularity at the surface of the femoral head. Cross-section of the right femoral head showed a concave fracture line in the subchondral bone. Based on these findings, bilateral subchondral insufficiency fracture of the femoral head was diagnosed.