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Avascular necrosis (AVN), also called osteonecrosis or bone infarction, is death of bone tissue due to interruption of the blood supply. [1] Early on, there may be no symptoms. [1] Gradually joint pain may develop, which may limit the person's ability to move. [1] Complications may include collapse of the bone or nearby joint surface. [1]
The major tissues affected are nerves and muscles, where irreversible damage starts to occur after 4–6 hours of cessation of blood supply. [4] Skeletal muscle, the major tissue affected, is still relatively resistant to infarction compared to the heart and brain because its ability to rely on anaerobic metabolism by glycogen stored in the cells may supply the muscle tissue long enough for ...
Dysbaric osteonecrosis or DON is a form of avascular necrosis where there is death of a portion of the bone that is thought to be caused by nitrogen (N 2) embolism (blockage of the blood vessels by a bubble of nitrogen coming out of solution) in divers. [1]
Over time, healing occurs by new blood vessels infiltrating the dead bone and removing the necrotic bone which leads to a loss of bone mass and a weakening of the femoral head. [9] The bone loss leads to some degree of collapse and deformity of the femoral head and sometimes secondary changes to the shape of the hip socket. [citation needed]
The condition is usually characterized by a sudden onset of knee pain, worse at night, or during weight-bearing such as standing or running. Nevertheless, it can also occur during rest or without any weight-bearing. About 94% of the cases affect the medial condyle of the femur. This is because the blood supply for the medial condyle is less ...
Coagulative necrosis occurs primarily in tissues such as the kidney, heart and adrenal glands. [6] Severe ischemia most commonly causes necrosis of this form. [8] Liquefactive necrosis (or colliquative necrosis), in contrast to coagulative necrosis, is characterized by the digestion of dead cells to form a viscous liquid mass. [7]
Necrotic bone does not undergo resorption; therefore, it appears relatively more opaque. Attempts at repair of ischaemic-damaged bone will usual occur in 2 phases. First, when dead bone abuts live marrow, capillaries and undifferentiated mesenchymal cells grow into the dead marrow spaces, while macrophages degrade dead cellular and fat debris ...
The crescent sign is caused by the necrotic and repair processes that occur during avascular necrosis. [1] [2] Osteosclerosis occurs at a margin where new bone is placed over dead trabeculae. [1] When the trabeculae experience stress leading to microfractures and collapse, the crescent sign appears. [1]