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 of avascular necrosis may develop in more than 20 percent of people who dislocate their hip joint.

Who Is Likely To Develop Avascular Necrosis?

Avascular necrosis strikes 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.

Magnetic Resonance Imaging (MRI)

MRI is quickly becoming a common method for diagnosing avascular necrosis. Unlike x rays, bone scans, and CT (computed/computerized tomography) scans, MRI detects chemical changes in the bone marrow and can show avascular necrosis in i ts earliest stages. MRI provides the doctor with a picture of the area affected and the bone rebuilding process. In addition, MRI may show diseased areas that are not yet causing any symptoms.

The goal in treating avascular necrosis is to improve the patient's use of the affected joint, stop further damage to the bone, and ensure bone and joint survival. To reach these goals, the doctor may use one or more of the following treatments:

Osteotomy

This surgical procedure reshapes the bone to reduce stress on the affected area. There is a lengthy recovery period, and the patient's activities are very limited for 3 to 12 months after an osteotomy. This procedure is most effective for patients with advanced avascular necrosis and those with a large area of affected bone.

The goal in treating avascular necrosis is to improve the patient's use of the affected joint, stop further damage to the bone, and ensure bone and joint survival. To reach these goals, the doctor may use one or more of the following treatments:

Reduced Weight Bearing

If avascular necrosis is diagnosed early, the doctor may begin treatment by having the patient remove weight from the affected joint. The doctor may recommend limiting activities or using crutches. In some cases, reduced weight bearing can slow the damage caused by avascular necrosis and permit natural healing. When combined with medication to reduce pain, reduced weight bearing can be an effective way to avoid or delay surgery for some patients. Most patients eventually will need surgery, however, to repair the joint permanently.

What Research Is Being Done To Help People With Avascular Necrosis?

With proper treatment, most people with avascular necrosis can lead normal lives. But there is still a lot to learn about prevention, diagnosis, and treatment. For example, researchers are studying:

* New ways to diagnose avascular necrosis in its earliest stages, when non- surgical treatment is most likely to help.

* The various causes of avascular necrosis so that, someday, it may be possible to prevent the disease.

* New treatments and improvement of the treatments that are available. In the future, medication may be an effective treatment for avascular necrosis.

· Improvements to the various types of hip replacements, to prevent younger patients from needing more than one hip replacement during their life.

Other Risk Factors

Other risk factors or conditions associated with non-traumatic avascular necrosis include Gaucher's disease, pancreatitis, radiation treatments and chemotherapy, decompression disease, and blood disorders such as sickle cell disease.

Steroid Medications

Corticosteroids such as prednisone are commonly used to treat diseases in which there is inflammation, such as systemic lupus erythematosus, rheumatoid arthritis, and vasculitis. Studies suggest that long-term, systemic (oral or intravenous) corticosteroid use is associated with 35 percent of all cases of non-traumatic avascular necrosis. However, there is no known risk of avascular necrosis 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 lead 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 (when occurring in the hip) than avascular necrosis resulting from other causes.

What Are the Symptoms?

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 collapses, pain may develop or increase dramatically. Pain may be severe enough to limit the patient's range of motion in the affected joint. The period of time between the first symptoms and loss of joint function is different for each patient, ranging from several months to more than a year.

The goal in treating avascular necrosis is to improve the patient's use of the affected joint, stop further damage to the bone, and ensure bone and joint survival. To reach these goals, the doctor may use one or more of the following treatments:

Arthroplasty/Total Joint Replacement

Total joint replacement is the treatment of choice in late-stage avascular necrosis and when the joint is destroyed. In this surgery, the diseased joint is replaced with artificial parts. It may be recommended for people who are not good candidates for other treatments, such as patients who do not do well with repeated attempts to preserve the joint.

Various types of replacements are available, and people should discuss specific needs with their doctor.

What Treatments Are Available?

Appropriate treatment for avascular necrosis is necessary to keep joints from breaking down. If untreated, most patients will suffer 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.

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, 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.

X Ray

An x ray is a common tool that the doctor may use to help diagnose the cause of joint pain. It is a simple way to produce pictures of bones. The x ray of a person with early avascular necrosis is likely to be normal because x rays are not sensitive enough to detect the bone changes in the early stages of the disease. X rays can show bone damage in the later stages, and once the diagnosis is made, they are often used to monitor the course of the condition.

Where Can I Find More Information About Avascular Necrosis?

Arthritis Foundation
1330 West Peachtree Street
Atlanta, GA 30309
404/872-7100
800/283-7800 or call your local chapter (listed in the telephone directory)
World Wide Web address: http://www.arthritis.org

The Hip Society
c/o Richard B. Welch, M.D.
One Shrader Street, Suite 650
San Francisco, CA 94117
415/221-0665
Fax: 415/221-4023
The Society maintains a list of physicians who are specialists in problems of the hip and provides physician referrals by geographic area.

Acknowledgments

The NIAMS gratefully acknowledges the assistance of Thomas D. Brown, Ph.D., of the University of Iowa; James Panagis, M.D., M.P.H., of the National Institutes of Health; and Harry E. Rubash, M.D., of the University of Pittsburgh Medical Center, in the preparation and review of this fact sheet.

The National Arthritis and Musculoskeletal and Skin Diseases Information Clearinghouse (NAMSIC) is a public service sponsored by the NIAMS that provides health information and information sources. The NIAMS, a part of the National Institutes of Health (NIH), leads the Federal medical research effort in arthritis and musculoskeletal and skin diseases. The NIAMS sponsors research and research training throughout the United States as well as on the NIH campus in Bethesda, MD, and disseminates health and research information.