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Aseptic bone necrosis (ABN), also called avascular necrosis or osteonecrosis, is where bone and marrow die in the absence of an infective agent. It can affect any bone, and half of cases show multiple sites of damage, but primarily affects the joints at the shoulder, knee, and hip.
The condition shows necrosis anywhere in the bone. Damage within the length of the bone is usually asymptomatic. Necrosis in the epiphysis or in the bone joints, which extends into adjacent cartilage is more serious. All dead bone cells are, eventually, reabsorbed and replaced. But new bone is soft, may misshape or fracture under pressure producing malformed joint surfaces and hence pain and mobility problems, afflictions such as arthritis. This joints must be treated surgically, by replacement.
It can be caused by a number of conditions that damage bone cells, including fractures, vascular compression, hypertension, vasculitis, thrombosis, the use of corticosteroids, and damage from radiation.
It can also be found in divers, around 5% of professional divers develop ABN, as a consequence of inadequate decompression. Insufficient to produce sickness but producing nitrogen bubbles which block blood circulation in some bone areas.