Definition of Osteonecrosis:

Osteonecrosis is bone death caused by poor blood supply to the area. It is most common in the hip and shoulder.

Causes, incidence, and risk factors:

Osteonecrosis occurs when part of the bone does not get blood and dies. After a while the bone can break off. If this condition is not treated, bone damage gets worse. Eventually, the affected part of the bone may collapse.

Osteonecrosis can be caused by disease, or a severe trauma, such as a break or dislocation, that affects the blood supply to the bone. Many times, no trauma or disease is present. This is called "idiopathic osteonecrosis" -- meaning it occurs without any known cause.

The following can cause osteonecrosis:

• Long-term treatments with steroids
• Excessive alcohol use
• Sickle cell disease
• Radiation therapy
• Gaucher disease
• Decompression sickness
• Dislocation or fractures around a joint

Some diseases that may be associated with the development of this condition include:

• Gout
• Atherosclerosis
• Diabetes

Osteonecrosis is most common in people between ages 30 and 60. Most cases in adults occur at the hip joint. The condition can also occur due to childhood cancer therapy.

Legg-Calvé-Perthes disease is a similar condition seen in children and adolescents.

Symptoms:

There are no symptoms in the early stages. As bone damage worsens, you may have the following symptoms:

• Pain in the joint that may increase over time, and will become very severe if the bone collapses
• Pain that occurs even at rest
• Limited range of motion
• Groin pain, if the hip joint is affected
• Limping, if the condition occurs in or below the hips

Signs and tests:

Your health care provider will do a complete physical exam to find out if you have any diseases or conditions that may affect your bones. You will be asked questions about your symptoms and medical history. The questions might include:

• When did the pain start?
• Does the pain spread (radiate) anywhere?
• Is the pain constant, or does it get better at night or at rest?
• Have you noticed any difference in how much or how far you can move (your mobility)?
• Do pain relievers help?
• Are you taking any steroids now, or have you ever taken them?
• Do you drink alcohol? If so, how much?

Be sure to let your health care provider know about any medications or vitamin supplements you are taking, even over-the-counter medicine.

After the exam, your health care provider will order one or more of the following tests:

• X-ray
• MRI
• Bone scan
• CT scan

Treatment:

If your health care provider knows the reason for osteonecrosis, part of the treatment will be aimed at the underlying condition. For example, if a blood clotting disorder is the reason, treatment will consist, in part, of clot-dissolving medicine.

If the condition is caught very early, you will take pain relievers and limit use of the affected area. This may include using crutches if your hip, knee, or ankle is affected. You may need to do range-of-motion exercises. Nonsurgical treatment can often slow the progression of osteonecrosis, but most people will need surgery.

Surgical options include:

• A bone graft
• A bone graft along with its blood supply (vascularized bone graft)
• Cutting the bone and changing its alignment to relieve stress on the bone or joint (osteotomy)
• Total joint replacement
• Removing part of the inside of the bone (core decompression) to relieve pressure and allow new blood vessels to form

Support Groups:

You can find more information and support resources at the following organizations:

• National Osteonecrosis Foundation -- www.nonf.org
• ON/AVN Support Group Int' l Association --http://osteonecrosisavnsupport.org
• The Arthritis Foundation -- www.arthritis.org
• Center for Osteonecrosis Research and Education (CORE) -- http://www.osteonecrosis.org

Expectations (prognosis):

Prognosis depends on the following:

• Stage of the disease when it was diagnosed
• Size of the area of bone involved
• Whether any other conditions were involved
• Age and general health of the person affected

The outcome can vary from complete healing to permanent damage in the affected bone.

Complications:

Advanced osteonecrosis can lead to osteoarthritis and permanent decreased mobility. Severe cases may require joint replacement.

Calling your health care provider:

Prevention:

Many cases of osteonecrosis do not have a known cause, so prevention may not be possible. However, in some cases, you can reduce your risk by doing the following:

• Avoid drinking excessive amounts of alcohol.
• When possible, avoid high doses and long-term use of corticosteroids.
• Dive safely to avoid decompression sickness.