What is osteonecrosis of the femoral head? Femoral head necrosis is a type of ischemic necrosis of the femoral head, which can be compared to the “coronary heart disease” of the hip joint. There are many factors that cause ischemic necrosis, and the disease naturally progresses rapidly, often leading to femoral head collapse and osteoarthritis at a later stage, and patients have a high disability rate. The disease is common in young patients and seriously affects their quality of life. What are the possible causes of femoral head necrosis? Femoral head necrosis may be associated with the following factors: trauma (fractures, dislocations, etc.), hormonal therapy, radiation therapy, alcoholic connective tissue disease, infections, etc. Some of the factors that can increase the risk of femoral head necrosis are: smoking, obesity, diabetes, hyperlipidemia, hypertension, etc. The disease can occur in about 30% of patients with collagen disease and sickle cell anemia. In addition organ transplantation, diffuse intravascular coagulation may be associated with the disease. How does osteonecrosis of the femoral head develop? Femoral head necrosis is the result of a combination of disruption of blood flow to the femoral head and defects in osteochondral repair, involving several mechanisms: 1) mechanical destruction of the femoral head, such as periprosthetic fractures; 2) external pressure acting on the local vascular wall, such as vasculitis, patients receiving radiation therapy; 3) arterial thrombosis or embolism, such as sickle cell hemolysis, hormones, alcohol; 4) venous vascular occlusion, such as infection . After the onset of ischemic necrosis of the femoral head, progressive vascular damage and weak collateral circulation will lead to irreversible lesions of the femoral head. Spasm of blood vessels is also an auxiliary cause for the development of necrosis. How is femoral head necrosis staged? Ischemic necrosis of the femoral head with clinical symptoms and confirmed by woven biopsy is divided into four stages according to the x-ray performance. Stage II has normal femoral head appearance, but there are obvious signs of bone repair, including cystic degeneration and osteosclerosis. The radiolucent area seen on the X-ray shows histologically as a bone resorption area and corresponding fibrous or granulation tissue. The osteosclerotic area is histologically represented by new bone overlying the dead bone at the edge of the necrotic area. In stage III, there is subchondral bone collapse or flattening of the femoral head. Stage IV shows joint space narrowing and secondary degenerative changes in the acetabulum (cystic degeneration, marginal bone formation, and cartilage destruction). Patients who are clinically asymptomatic and have no changes on X-ray, but whose MRI (magnetic resonance imaging) shows a double line sign, can also be classified as stage 0. How is femoral head necrosis diagnosed? The current method of diagnosing femoral head necrosis mainly relies on imaging examinations, specifically X-rays, CT, MRI, isotope bone scan, etc., among which MRI and others can detect early lesions. Of course, the patient’s medical history is also very important in the diagnosis of osteonecrosis of the femoral head. How to treat osteonecrosis of the femoral head? For early stage of femoral head necrosis, conservative treatment methods can be used, such as the use of Chinese herbal medicine, regulation of blood lipids, stopping or reducing the use of hormones, appropriate physical therapy, or the use of hyperbaric oxygen and other treatment methods. Conservative treatment is not effective or late stage of femoral head necrosis can be treated by surgery, which mainly includes: femoral head medullary decompression, osteotomy, bone flap grafting with anastomosis, artificial joint replacement, etc. Depending on the patient’s condition, different treatments can be chosen. Of course, there are many treatment methods for femoral head necrosis, and different treatment methods are chosen according to different necrosis types, different ages, different occupational requirements and different economic conditions.