It 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 is also associated with long-term use of high-dose steroid medications and excessive alcohol intake.
Anyone can be affected by avascular necrosis. However, it's most common in people between the ages of 30 and 60. Because of this relatively young age range, avascular necrosis can have significant long-term consequences.
Osteonecrosis can be in one or several bones. It is most common in the upper leg. Other common sites are your upper arm and your knees, shoulders and ankles. The disease can affect men and women of any age, but it is mention above it usually strikes in thirties, forties or fifties.
Many people have no symptoms in the early stages of avascular necrosis. As the condition 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. Pain associated with avascular necrosis of the hip may be focused in the groin, thigh or buttock. In addition to the hip, the areas likely to be affected are the shoulder, knee, hand and foot.
Some people develop avascular necrosis bilaterally — for example, in both hips or in both knees.
The causes of osteonecrosis are divided into two categories: post-traumatic osteonecrosis and non-traumatic osteonecrosis.
Post-traumatic osteonecrosis refers to the onset of the bone condition after experiencing a significant trauma. A severely broken bone or dislocated joint is typically the underlying cause behind the development of osteonecrosis.
Non-traumatic osteonecrosis refers to the onset of the bone condition for reasons unrelated to a physical trauma. People may be more susceptible to development of the bone condition if they have a history of diseases or activities known to disrupt blood supply, such as alcoholism, smoking, blood clotting disorders, kidney disease, connective tissue disease, lupus, or have undergone treatment with high levels of corticosteroids. Oftentimes the condition has unknown causes and is referred to as an idiopathic case of osteonecrosis. More recently, a family of drugs called bisphosphonates has been linked with the development of non-traumatic osteonecrosis.
It occurs when blood flow to a bone is interrupted or reduced. Reduced blood supply can be caused by:
- Joint or bone trauma. An injury, such as a dislocated joint, might damage nearby blood vessels. Cancer treatments involving radiation also can weaken bone and harm blood vessels.
- Fatty deposits in blood vessels. The fat (lipids) can block small blood vessels, reducing the blood flow that feeds bones.
- Certain diseases. Medical conditions, such as sickle cell anemia and Gaucher's disease, also can cause diminished blood flow to bone.
For about 25 percent of people with avascular necrosis, the cause of interrupted blood flow is unknown.
Risk factors include:
- Long-term steroid treatment
- Alcohol abuse
- Joint injuries
- Having certain diseases, including arthritis and cancer
To minimize the risk of osteonecrosis caused by corticosteroids, doctors use these drugs only when essential, prescribe them in as low a dose as needed, and prescribe them for as short a duration as possible. To prevent osteonecrosis caused by decompression sickness, people should follow accepted rules for decompression during diving and when working in pressurized environments.
Excessive alcohol use and smoking should be avoided.
Various drugs (such as those that prevent blood clots, dilate blood vessels, or lower lipid levels) are being evaluated for prevention of osteonecrosis in people at high risk.
Keep cholesterol levels low. Tiny bits of fat are the most common substance blocking blood supply to bones.
- The earlier an osteonecrosis diagnosis can be made, the better the chances are of limiting the severe and long-term affects of the painful bone condition. If a case of osteonecrosis goes untreated, it can eventually culminate in bone collapse. The best method for early osteonecrosis diagnosis is MRI (Magnetic Resonance Imaging). An MRI can detect the onset of osteonecrosis before the condition has had ample time to cause significant damage to the affected bone(s).
- It is not until the bone condition has progressed to a serious stage that its effects can be viewed via x-ray, at which point it typically includes joint involvement.
- Bone Scan
- Bone X-Ray
- CT -- Body
Appropriate treatment for osteonecrosis is necessary to keep joints from breaking down. Without treatment, most people with the disease will experience severe pain and limitation in movement within 2 years. To determine the most appropriate treatment, the doctor considers the following:
- The age of the patient
- The stage of the disease (early or late)
- The location and whether bone is affected over a small or large area
- The underlying cause of osteonecrosis.
The goal is to prevent further bone loss. Specific treatment usually depends on the amount of bone damage you already have.
Medications and therapy:
In the early stages of avascular necrosis, symptoms can be reduced with medication and therapy. Your doctor might recommend:
- Nonsteroidal anti-inflammatory drugs. Medications, such as ibuprofen (Advil, Motrin IB, others) or naproxen sodium (Aleve, others) may help relieve the pain and inflammation associated with avascular necrosis.
- Osteoporosis drugs. Medications, such as alendronate (Fosamax, Binosto), may slow the progression of avascular necrosis, but the evidence is mixed.
- Cholesterol-lowering drugs. Reducing the amount of cholesterol and fat in your blood may help prevent the vessel blockages that can cause avascular necrosis.
- Blood thinners. If you have a clotting disorder, blood thinners, such as warfarin (Coumadin, Jantoven), may be recommended to prevent clots in the vessels feeding your bones.
- Rest. Reducing the weight and stress on your affected bone can slow the damage. You might need to restrict your physical activity or use crutches to keep weight off your joint for several months.
- Exercises. You may be referred to a physical therapist to learn exercises to help maintain or improve the range of motion in your joint.
- Electrical stimulation. Electrical currents might 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 avascular necrosis is fairly advanced, your doctor may recommend surgery. The options include:
- Core decompression. The 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). In this procedure, a wedge of bone is removed above or below a weight-bearing joint, to help shift your weight off the damaged bone. Bone reshaping might allow you to postpone joint replacement.
- Joint replacement. If your diseased bone has already collapsed or other treatment options aren't helping, you might need surgery to replace the damaged parts of your joint with plastic or metal parts. An estimated 10 percent of hip replacements in the United States are performed to treat avascular necrosis of the hip.
- Regenerative medicine treatment. Bone marrow aspirate and concentration is a novel procedure that in the future might be appropriate for early stage avascular necrosis of the hip. Stem cells are harvested from your bone marrow. During surgery a core of dead hip bone is removed and stem cells inserted in its place, potentially allowing for growth of new bone.
- Mayo Clinic