Avascular Necrosis

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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 necrosis, and ischemic bone necrosis.

Although it can happen in any bone, it most commonly affects the ends of long bones such as the femur, the bone extending from the knee joint to the hip joint. Other common sites include the upper arm bone, knees, shoulders, and ankles. The disease may affect just one bone, more than one bone at the same time, or more than one bone at different times. It usually affects people between 30 and 50 years of age; about 10,000 to 20,000 people develop this disease each year. Orthopaedic doctors most often diagnose the disease.

The amount of disability that results from this disease 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 this disease, 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.

This disease affects both men and women and affects people of all ages. It is most common among people in their thirties and forties. Depending on a person's risk factors and whether the underlying cause is trauma, it also can affect younger or older people.

It may cause no signs or symptoms. But some people experience pain or a loss of range of motion in the affected joint. Where you experience pain depends on where the the disease occurs. For instance:

  • HIP may cause pain in your groin. Pain may radiate down your thigh to your knee. Pain is usually worse when standing or walking.
  • WRIST may cause wrist pain and finger weakness. You might feel less pain when you keep your hand still. The wrist bones most commonly associated include the Kienbock disease and Preiser disease.
  • KNEE causes knee pain. The bone most commonly affected is the lower end of the thighbone.
  • SHOULDER usually involves the head of your upper arm bone. Pain and stiffness are common.

  • It may also develop in the bones of your foot, ankle, spine and jaw.

    Avascular necrosis has several causes. Loss of blood supply to the bone can be caused by an injury or by certain risk factors, such as some medications, blood coagulation disorders, or excessive alcohol use. Increased pressure within the bone also is associated with this disease. The pressure within the bone causes the blood vessels to narrow, making it hard for the vessels to deliver enough blood to the bone cells.

  • Injury: When a joint is injured, as in a fracture or dislocation, the blood vessels may be damaged. This can interfere with the blood circulation to the bone and lead to trauma-related avascular necrosis. Studies suggest that this type may develop in more than 20% of people who dislocate their hip joint.

  • Steroid Medications: Corticosteroids such as prednisone are commonly used to treat diseases in which there is inflammation, such as systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease, and vasculitis. Studies suggest that long-term, systemic (oral or intravenous) corticosteroid use is associated with 35% of all cases of nontraumatic avascular necrosis. However, there is no known risk associated with the limited use of steroids. Patients should discuss concerns about steroid use with their doctor.

    Doctors aren't sure exactly why the use of corticosteroids sometimes leads to avascular necrosis. They may interfere with the body's ability to break down fatty substances. These substances then build up in and clog the blood vessels, causing them to narrow. This reduces the amount of blood that gets to the bone. Some studies suggest that corticosteroid-related avascular necrosis is more severe and more likely to affect both hips than it resulting from other causes.

  • Alcohol Use: Excessive alcohol use and corticosteroid use are two of the most common causes of nontraumatic avascular necrosis. In people who drink an excessive amount of alcohol, fatty substances may block blood vessels, causing a decreased blood supply to the bones that results in avascular necrosis.

  • Other Risk Factors: Other risk factors or conditions associated with nontraumatic avascular necrosis include Gaucher's disease, pancreatitis, radiation treatments and chemotherapy, decompression disease, and blood disorders such as sickle cell disease.

  • Treatments:
    Appropriate treatment is necessary to keep joints from breaking down. If untreated, most patients will experience severe pain and limitation in movement within 2 years. Several treatments are available that can help prevent further bone and joint damage and reduce pain. To determine the most appropriate treatment, the doctor considers the following aspects of a patient's disease:
  • The age of the patient
  • The stage of the disease - early or late
  • The location and amount of bone affected - a small or large area
  • The underlying cause of avascular necrosis - with an ongoing cause such as corticosteroid or alcohol use, treatment may not work unless use of the substance is stopped.

  • The goal in treating this disease is to improve the patient's use of the affected joint, stop further damage to the bone, and ensure bone and joint survival.

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