The International Association for Research in Osseous Circulation (ARCO) defines femoral head necrosis as a disease in which the blood supply to the femoral head is interrupted or impaired, causing the death and subsequent repair of bone cells and bone marrow components, followed by structural changes in the femoral head, femoral head collapse, and joint dysfunction. At present, the diagnosis, staging and typing of femoral head necrosis are not very clear in northern Jiangsu Province, which directly leads to blind and non-standardized treatment of femoral head necrosis. Especially, the treatment of early and mid-stage femoral head necrosis is not standardized. The common factors that cause femoral head necrosis are as follows: 1. Traumatic factors: history of hip trauma such as femoral neck fracture or hip joint dislocation. 2, non-traumatic factors: long-term or large amounts of hormones, alcohol drinkers, divers, pilots can also suffer from this disease. Generally, large doses of hormones can cause symptoms a few months to a year or so after use. In the northern part of Jiangsu Province, the disease is not uncommon in long-term high-dose drinkers. Clinical symptoms and signs of femoral head necrosis: hip pain, mainly in the groin area and hip and thigh pain. Limp and prolonged walking weakness appear on walking. Examination of the hip joint: pain is aggravated when the hip joint is restricted in internal rotation and internal rotation. Deep pressure pain and percussion pain around the affected hip joint. The most common areas of pressure pain are located in the groin area, the greater trochanter and axial percussion pain in the heel. The “4” test was positive. By taking a history and examining the body, we must perform, imaging examinations in patients suspected of having femoral head necrosis. Ordinary Χ-ray examination is convenient and inexpensive, easily accepted by the majority of patients, but Χ-ray is only a response to the mineral content of the bone, until the bone resorption, does not show any Χ-ray performance, so it is not significant for the early diagnosis of femoral head necrosis, the diagnosis can be made for necrotic femoral head whose calcium composition has been changed. CT scan can obtain high resolution and exact axial tomographic images, which can make a more accurate diagnosis of the femoral head; CT examination can show lesions that cannot be detected by conventional X-ray, and the image of the lesion is clearer than X-ray. MRI is the most sensitive method for early diagnosis of femoral head necrosis. For patients who are considered to have femoral head necrosis, MRI is necessary when the diagnosis cannot be made clearly by X-ray and CT. For patients with femoral head necrosis, we usually perform two types of X-ray examinations: flat film of the affected hip and frog position: early femoral head necrosis can be seen as uneven osteoporosis, with alternating low-density and high-density areas; later, cystic degeneration of the femoral head can be seen, with the appearance of surrounding sclerotic zones; subchondral bone collapse (crescent sign); in severe cases, the femoral head collapses and flattens, and the femoral neck becomes shorter; the hip joint is subluxed, and the joint space becomes narrower. Osteoarthritis appears. Patients who are considered to have femoral head necrosis should also undergo CT examination of the hip joint. CT of the hip joint can further clarify whether the acetabulum is involved, the location and extent of femoral head necrosis, and whether the subchondral bone is damaged. In the early stage of femoral head necrosis, CT examination can show that the trabecular structure is disturbed, reduced or disappeared. In the middle and late stages, CT examination can see the disappearance of bone trabeculae, cavity formation and the extent of sclerotic bone around the necrotic area, which is helpful for what treatment method and surgical operation to be taken. At present, MRI is the most early and definitive non-invasive test to diagnose femoral head necrosis. In the early stage of femoral head necrosis, the pathological essence is necrosis of bone cells and bone marrow cells, and the organic component is gradually lost, while the trabecular structure, which is mainly composed of calcium deposits, is not yet damaged, and the destruction of the trabecular structure will only appear after several months of femoral head necrosis, usually 3-6 months, so the X-ray performance can be normal. MRI examination reflects the change of hydrogen ions. The apoptosis of bone cells and bone marrow cells has occurred after 6 hours of femoral osteonecrosis, which mainly shows the change of organic components, among which the change of hydrogen ion concentration is the most obvious. Half a month after femoral osteonecrosis, the change of hydrogen ion concentration reaches the level visible by MRI. Therefore, it is necessary for us to perform MRI examination of the hip joint in patients suspected of having osteonecrosis of the femur after no positive findings on X-ray examination. For patients with hip pain, it is not difficult to diagnose osteonecrosis of the femoral head by combining the history of long-term hormone use, history of alcohol consumption, history of trauma, clinical symptoms and signs, and X-ray, CT and MRI examinations of the hip joint. The difficulty of femoral head necrosis lies in how to educate patients and how to have a clear understanding of the nature of its development, treatment options and social hazards. The difficulty is to carry out systematic treatment and how to delay its course and reduce the disability rate.