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Avascular necrosisBy Mayo Clinic staff
Original Article: http://www.mayoclinic.com/health/avascular-necrosis/DS00650
Avascular necrosis is the death of bone tissue due to a lack of blood supply. Also called osteonecrosis, avascular necrosis can lead to tiny breaks in the bone and the bone's eventual collapse.
The blood flow to a section of bone can be interrupted if the bone is fractured or the joint becomes dislocated. Avascular necrosis of bone is also associated with long-term use of high-dose steroid medications and excessive alcohol intake.
The hip is the joint most commonly affected by avascular necrosis. While avascular necrosis of bone can happen to anyone, it usually occurs in men between the ages of 30 and 60.
Many people have no symptoms in the early stages of avascular necrosis of bone. As the disease worsens, your affected joint may hurt only when you put weight on it. Eventually, the joint may hurt even when you're lying down.
Pain can be mild or severe and usually develops gradually. Joints most likely to be affected are the hip, shoulder, knee, hand and foot. Pain associated with avascular necrosis of the hip may be focused in the groin, thigh or buttock. Some people experience avascular necrosis bilaterally — for example, in both hips or in both knees.
When to see a doctor
See your doctor if you experience persistent pain in any joint. Seek immediate medical attention if you believe you have a broken bone or a dislocated joint.
Avascular necrosis occurs when blood flow to a bone is interrupted or reduced, which may be caused by:
- Joint or bone injury. A traumatic injury, such as a dislocated joint, may reduce the blood supply to a section of bone, leading to bone death. Cancer treatments involving radiation also can weaken bone and harm blood vessels.
- Pressure inside the bone. Some medical conditions, such as sickle cell anemia or Gaucher's disease, can increase the pressure inside the bone — making it more difficult for fresh blood to enter.
Your risk of developing avascular necrosis can be increased by certain diseases, medical treatments or excessive drinking.
Several alcoholic drinks a day for several years can cause fatty deposits to form in your blood vessels. This can restrict the flow of blood to your bones. The more alcohol you habitually drink every day, the higher your risk of avascular necrosis.
Certain types of medications can increase your risk of avascular necrosis. Examples include:
- Steroids. Taken at high doses and for long periods of time, corticosteroids, such as prednisone, increase your risk of avascular necrosis. Like alcohol, these drugs may increase the amount of fat in your blood, leading to blockage of the small vessels feeding your bones. Doctors often prescribe high doses of corticosteroids for diseases such as vasculitis or lupus.
- Osteoporosis drugs. People who take bisphosphonates — a type of medicine used to help strengthen bones weakened by osteoporosis — sometimes develop osteonecrosis of the jaw. This risk is higher for people who have received large doses of bisphosphonates intravenously to counteract the damage caused by cancer in the bones.
Some underlying medical conditions increase your risk of developing avascular necrosis. They include:
- Sickle cell anemia
Several types of medical procedures increase your risk of avascular necrosis. Examples include:
- Cancer treatments such as radiation
- Dialysis, a process to clean the blood after kidney failure
- Kidney and other organ transplants
Avascular necrosis that goes untreated will worsen with time. Eventually the bone may become weakened enough that it collapses. When the bone loses its smooth shape, severe arthritis can result.
Preparing for your appointment
Although you may initially bring your signs and symptoms to the attention of your family doctor, he or she may refer you to a doctor who specializes in disorders of the joints (rheumatologist) or to an orthopedic surgeon.
What you can do
Before your appointment, you may want to prepare a list that answers the following questions:
- Have you ever injured this joint in the past?
- What other medical conditions, if any, do you have?
- Are there health problems that tend to run in your family?
- What types of medications and supplements do you take?
What to expect from your doctor
Your doctor will probably ask some of the following questions:
- Where exactly does it hurt?
- Does any particular joint position make the pain better or worse?
- How long have you had this pain?
- Have you ever taken steroids, such as prednisone?
- How much alcohol do you drink?
Tests and diagnosis
During the exam, your doctor will press around your joint, checking for tenderness. He or she may also move your joints through a variety of positions to see if your range of motion has been reduced.
Many disorders can cause joint pain. Imaging tests can help pinpoint the proper diagnosis.
- X-rays. In the early stages of avascular necrosis, X-rays usually appear normal. But X-rays can often reveal bone changes that occur in later stages of the disease.
- Bone scan. For a bone scan, a small amount of radioactive material is injected into your vein. This material then travels to the parts of your bones that are injured or healing, and shows up as bright spots on the imaging plate.
- Magnetic resonance imaging (MRI). MRI scans can show early changes in the bone that may indicate avascular necrosis. MRI uses radio waves and a strong magnetic field to produce detailed images of internal structures.
Treatments and drugs
The treatment goal for avascular necrosis is to prevent further bone loss. What treatment you receive depends on the amount of bone damage you already have.
In some people, avascular necrosis symptoms may be reduced with medications such as:
- Nonsteroidal anti-inflammatory drugs (NSAIDs). Medications such as ibuprofen (Advil, Motrin, others) or naproxen (Aleve) may help relieve the pain and inflammation associated with avascular necrosis.
- Osteoporosis drugs. Some studies indicate that osteoporosis medications, such as alendronate (Fosamax, Binosto), may slow the progression of avascular necrosis.
- Cholesterol drugs. Reducing the amount of fat (lipids) in your blood may help prevent the vessel blockages that often cause avascular necrosis.
- Blood thinners. If you have a clotting disorder, blood thinners such as warfarin (Coumadin, Jantoven) may be prescribed to prevent clots in the vessels feeding your bones.
In the early stages of avascular necrosis, your doctor might suggest:
- Rest. Reducing the amount of weight and stress on your affected bone may slow the damage of avascular necrosis. You may need to restrict the amount of physical activity you engage in. In the case of hip or knee avascular necrosis, you may need to use crutches to keep weight off your joint for several months.
- Exercises. Certain exercises may help you maintain or improve the range of motion in your joint. A physical therapist can choose exercises specifically for your condition and teach you how to do them.
- Electrical stimulation. Electrical currents may encourage your body to grow new bone to replace the area damaged by avascular necrosis. Electrical stimulation can be used during surgery and applied directly to the damaged area. Or it can be administered through electrodes attached to your skin.
Surgical and other procedures
Because most people don't start having symptoms until the disease is fairly advanced, you may need to consider surgeries such as:
- Core decompression. In this operation, your surgeon removes part of the inner layer of your bone. In addition to reducing your pain, the extra space within your bone stimulates the production of healthy bone tissue and new blood vessels.
- Bone transplant (graft). This procedure can help strengthen the area of bone affected by avascular necrosis The graft is a section of healthy bone taken from another part of your body.
- Bone reshaping (osteotomy). This procedure removes a wedge of bone above or below a weight-bearing joint to help shift your weight off the damaged bone. Bone reshaping may allow you to postpone joint replacement.
- Joint replacement. If your diseased bone has already collapsed or other treatment options aren't helping, you may need surgery to replace the damaged parts of your joint with plastic or metal parts.
It's hard to tell if reducing your risk factors will help prevent avascular necrosis, but the following tips can also help improve your general health:
- Limit alcohol. Heavy drinking is one of the top risk factors for developing avascular necrosis.
- Keep cholesterol levels low. Tiny bits of fat (lipids) are the most common substance blocking blood supply to bones.
- Monitor steroid use. Make sure your doctor knows about any past or present use of high-dose steroids. Steroid-related bone damage appears to worsen with repeated courses of high-dose steroids.
- Firestein GS, et al. Kelley's Textbook of Rheumatology. 8th ed. Philadelphia, Pa.: Saunders Elsevier; 2009. http://www.mdconsult.com/das/book/body/208746819-6/0/1807/0.html. Accessed Feb. 28, 2012.
- Questions and answers about osteonecrosis (avascular necrosis). National Institute of Arthritis and Musculoskeletal and Skin Diseases. http://www.niams.nih.gov/Health_Info/Osteonecrosis/default.asp. Accessed Feb. 28, 2012.
- Jones LC. Osteonecrosis (avascular necrosis of bone). http://www.uptodate.com/index. Accessed Feb. 28, 2012.