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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 ]
This results in an increased bone resorption rate and a decreased bone mineral density due to increased pit numbers and pit areas in the bone. [ 18 ] [ 19 ] [ 20 ] Research has shown that viable osteocytes (another type of bone cell) may prevent osteoclastogenesis, whereas apoptotic osteocytes tend to induce osteoclast stimulation.
Particular medications can result in MRONJ, a serious but uncommon side effect in certain individuals. Such medications are frequently used to treat diseases that cause bone resorption such as osteoporosis, or to treat cancer. The main groups of drugs involved are anti-resorptive drugs, and anti-angiogenic drugs.
Experimental evidence suggests that bone cells composed of osteocytes, osteoclasts, and osteoblasts die within 12–48 hours, and marrow fat cells die within 120 hours. [17] The death of bone does not alter its radiographic opacity nor its mineral density. Necrotic bone does not undergo resorption; therefore, it appears relatively more opaque.
The pathophysiology of ORN is fairly complex and involves drastic changes to bone tissue as a result of DNA damage and cell death caused by radiation treatment. [3] Radiation therapy targeting tumor cells can affect normal cells as well, [4] [5] which can result in the death of bone tissue.
PTH increases bone resorption, leading to bone loss. A positive association exists between serum 1,25-dihydroxycholecalciferol levels and bone mineral density, while PTH is negatively associated with bone mineral density. [4] Tobacco smoking: Many studies have associated smoking with decreased bone health, but the mechanisms are unclear.
Osteolysis is an active resorption of bone matrix by osteoclasts and can be interpreted as the reverse of ossification.Although osteoclasts are active during the natural formation of healthy bone the term "osteolysis" specifically refers to a pathological process.
Osteoporosis is a bone-related disease caused by increased rates of bone resorption compared to bone formation. [39] A higher rate of resorption is often caused by increased osteoclastogenesis and results in symptoms of osteopenia such as excessive bone loss and low bone mineral density. [39]