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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]
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.
The three main mechanisms by which osteoporosis develops are an inadequate peak bone mass (the skeleton develops insufficient mass and strength during growth), excessive bone resorption, and inadequate formation of new bone during remodeling, likely due to mesenchymal stem cells biasing away from the osteoblast and toward the marrow adipocyte ...
The inhibition of osteoclast differentiation and function, precipitated by drug therapy, leads to decreased bone resorption and remodelling. [31] [39] Evidence also suggests bisphosphonates induce apoptosis of osteoclasts. [40] Another suggested factor is inhibition of angiogenesis due to bisphosphonates; this effect remains uncertain.
This form of therapy has been shown to prevent loss of bone mineral density (BMD) as a result of a reduction in bone turnover. However, bone health entails quite a bit more than just BMD. There are many other factors to consider. [citation needed] In healthy bone tissue there is a homeostasis between bone resorption and ossification.
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.
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] Osteoporosis is often triggered in post-menopausal women due to reduced estrogen levels associated with the depletion of hormone-releasing ovarian follicles. [40]
A sequestrum (plural: sequestra) is a piece of dead bone [1] that has become separated during the process of necrosis from normal or sound bone. It is a complication (sequela) of osteomyelitis. The pathological process is as follows: infection in the bone leads to an increase in intramedullary pressure due to inflammatory exudates