Ficat Staging System

Osteonecrosis of the femoral head is progressive in collapse of the femoral head and secondary osteoarthritis of the hip in 60–80% of the cases. However, when the necrosis is small and a considerable portion of the weight-bearing dome of the femoral head is viable, the disease is not progressive and patients are doing well for a prolonged time or during their whole life without any medical or surgical intervention. Thus, the classification of osteonecrosis should include the “stage,” which expresses the status of disease progression, and the “extent,” which describes the size of necrosis.