What is avascular necrosis?
Avascular necrosis of bone (AVN) (or aseptic necrosis or osteonecrosis), is a disease that results from poor blood supply to an area of bone causing bone death. This is a serious condition because the dead areas of bone do not function normally,
are weakened, and can collapse. Pain associated with avascular necrosis is often severe and unrelenting.
Avascular necrosis of bone is a disorder in which an avascular (lacking in blood supply) area of bone undergoes necrosis (dies). AVN is not common, but it is encountered in a certain number of patients with lupus. The area most often affected is the hip and in particular the upper part of the thigh bone (the femoral head) which makes up the ball of this ball-and-socket joint. This problem primarily affects younger adults. In 50 to 60 percent of cases it occurs in both hips. The goal for treatment of AVN is to save the natural hip joint if possible and not to have to replace the affected femoral head with an artificial joint. In order to accomplish this, early diagnosis is very important. Other bones may also be affected by AVN, but much less often than the hip. (These include the knee, the shoulder, and rarely the small bones of the wrist and the foot or ankle.) The following discussion will, therefore, focus on the hip.
Although it can happen in any bone, avascular necrosis most commonly affects the ends (epiphysis) of long bones such as the femur, the bone extending from the knee joint to the hip joint. The disease may affect just one bone, more than one bone at the same time, or more than one bone at different times. Avascular necrosis usually affects people between 30 and 50 years of age; about 10,000 to 20,000 people develop avascular necrosis each year.
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 torn away and 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. If left untreated, the disease progresses, the bone collapses, and the joint surface breaks down, leading to pain and arthritis.