OBJECTIVETo study early femoral head necrosis radiographic imaging features to provide objective basis for the clinical differential diagnosis and therapeutic schedule's choice.

METHODSNinty-one patients with femur head necrosis of ARCO stage I and II whom were diagnosed by clinic and MRI and treated from March 2007 to June 2008 were analyzed retrospectively. There were 32 males and 59 females with an average age of (34.83 +/- 9.57) years ranging from 21 to 60 years. The course of disease were from 2 to 12 months. There were 17 cases of unilateral and 74 of bilateral; 48 cases caused by steroid, 35 cases by alcohol and 8 cases for unknown reasons. The images of X-ray, CT and MRI of femoral head were analyzed to summarize the characteristic and to distinguish with the imaging of similar osteonecrosis.

RESULTSNinety-one cases had linear low signal on T1WI in weight-bearing area of femoral head and high signal of the "dual taxation" on T2WI. But the shapes had different characteristics. There were 36 cases (39.56%) of line type shapes, 28 cases (30.77%) of oval shapes, 14 cases (15.38%) of map-like shapes, 13 cases (14.29%) of wedge shapes. The X-rays of the disease similar to bone necrosis including primary hip osteoarthritis, developmental dysplasia of hip arthritis, femoral head epiphysitis (coxa plana), rheumatoid hip arthritis, hip arthritis of ankylosing spondylitis, transitional synovitis of hip joint, femoral head bone marrow edema etc, had the similar performance to femur head necrosis like cystic changes, joint space narrowing, femoral head deformation. MRI performance had their own characteristics.

CONCLUSIONMastering the image features of the early femoral head necrosis will help the early diagnosis and treatment of hip joint necrosis disease.