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Avascular necrosis is a disease resulting from the temporary or permanent loss of the blood supply to the bones. Without blood, the bone tissue dies and causes the bone to collapse. If the process involves the bones near a joint, it often leads to collapse of the joint surface. This disease also is known as osteonecrosis, aseptic (bone) necrosis, and ischemic bone necrosis.
In the early stages of avascular necrosis, patients may not have any symptoms. As the disease progresses, however, most patients experience joint pain - at first, only when putting weight on the affected joint, and then even when resting. Pain usually develops gradually and may be mild or severe. If avascular necrosis progresses and the bone and surrounding joint surface collapse, pain may develop or increase dramatically. Pain may be severe enough to limit the patient's range of motion in the affected joint.
A small number of cases of osteonecrosis of the jaw have been reported in people taking bisphosphonates for osteoporosis. These cases have primarily occurred after trauma to the jaw, such as a tooth extraction, or cancer treatment. Risk appears to be higher in people who have received bisphosphonates intravenously. While there is currently no clear evidence that you should stop taking bisphosphonates before dental surgery, let your dentist know what medications you're taking and discuss your concerns.
Early diagnosis and appropriate intervention can delay the need for joint replacement. However, most patients present late in the disease course. Without treatment, the process is almost always progressive, leading to joint destruction within 5 years. Patients taking corticosteroids and organ transplant recipients are particularly at risk of developing AVN. Most available data regarding the natural history, pathology, pathogenesis, and treatment of AVN pertains to femoral head necrosis.
Avascular necrosis of the femoral head (AVN) is an increasingly common cause of musculoskeletal disability as well as a major diagnostic and therapeutic challenge. Although initially patients are asymptomatic, AVN usually progresses to joint destruction, requiring total hip replacement (THR) in individuals, usually before the fifth decade. It is estimated that almost 10% of the nearly 500,000 THRs performed each year in the United States are intended to treat AVN at a cost of more than 1 billion dollars, approximately one fourth of the national budget for THR.
The amount of disability that results from avascular necrosis depends on what part of the bone is affected, how large an area is involved, and how effectively the bone rebuilds itself. The process of bone rebuilding takes place after an injury as well as during normal growth. Normally, bone continuously breaks down and rebuilds - old bone is reabsorbed and replaced with new bone. The process keeps the skeleton strong and helps it to maintain a balance of minerals. In the course of avascular necrosis, however, the healing process is usually ineffective and the bone tissues break down faster than the body can repair them.
The simplest surgical procedure is called core decompression, which involves taking a plug of bone out of the involved area. This procedure is very effective for early disease that has not yet progressed to bone collapse; it may even prevent collapse. Core decompression may also be used for someone younger than 50 whose bone has collapsed; this treatment may delay the need for a total joint replacement by several years because the person's pain is relieved or decreased. The procedure takes less than an hour to perform. The person must use crutches for 4 to 6 weeks afterward.