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Second, there is cellular differentiation of mesenchymal cells into osteoblasts or fibroblasts. First, there is angiogenesis and movement of undifferentiated mesenchymal cells from adjacent living bone tissue grow into the dead marrow spaces, as well as entry of macrophages that degrade dead cellular and fat debris. Upon reperfusion, repair of bone occurs in 2 phases. Experimental evidence suggests that bone cells ( osteocytes, osteoclasts, osteoblasts etc.) die within 12–48 hours, and that bone marrow fat cells die within 5 days. The hematopoietic cells are most sensitive to low oxygen and are the first to die after reduction or removal of the blood supply, usually within 12 hours. It can occur in the hip as part of Legg–Calvé–Perthes syndrome, and it can also occur as a result after malignancy treatment such as acute lymphoblastic leukemia and allotransplantation. In children, avascular osteonecrosis can have several causes. Prolonged, repeated exposure to high pressures (as experienced by commercial and military divers) has been linked to AVN, though the relationship is not well understood. īisphosphonates are associated with osteonecrosis of the mandible. The condition may also occur without any clear reason. Osteonecrosis is also associated with cancer, lupus, sickle cell disease, HIV infection, Gaucher's disease, and Caisson disease ( dysbaric osteonecrosis).
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Other risk factors include radiation therapy, chemotherapy, and organ transplantation. The main risk factors are bone fractures, joint dislocations, alcoholism, and the use of high-dose steroids. Other common sites include the humerus, knees, shoulders, ankles and the jaw. Īvascular necrosis most commonly affects the ends of long bones such as the femur. While it can affect any bone, about half of cases show multiple sites of damage. In many cases, there is pain and discomfort in a joint which increases over time. Males are more commonly affected than females. People 30 to 50 years old are most commonly affected. About 15,000 cases occur per year in the United States. Most of the time surgery is eventually required and may include core decompression, osteotomy, bone grafts, or joint replacement.
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Treatments may include medication, not walking on the affected leg, stretching, and surgery. Diagnosis is typically by medical imaging such as X-ray, CT scan, or MRI. Other relatively common sites include the upper arm bone, knee, shoulder, and ankle. The most commonly affected bone is the femur. Risk factors include bone fractures, joint dislocations, alcoholism, and the use of high-dose steroids. Complications may include collapse of the bone or nearby joint surface. Gradually joint pain may develop which may limit the ability to move. Medication, not walking on the affected leg, stretching, surgery Īvascular necrosis ( AVN), also called osteonecrosis or bone infarction, is death of bone tissue due to interruption of the blood supply.
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Osteopetrosis, rheumatoid arthritis, Legg–Calvé–Perthes syndrome, sickle cell disease Joint pain, decreased ability to move īone fractures, joint dislocations, alcoholism, high dose steroids Specimen removed during total hip replacement surgery. Head of the femur showing a flap of cartilage due to avascular necrosis ( osteochondritis dissecans). Osteonecrosis, bone infarction, aseptic necrosis, ischemic bone necrosis