Avascular necrosis (AVN), also called osteonecrosis, aseptic necrosis, or ischemic bone necrosis, is a condition that occurs when there is loss of blood to the bone. Because bone is living tissue that requires blood, an interruption to the blood supply causes bone to die. If not stopped, this process eventually causes the bone to collapse.
Who Gets Avascular Necrosis and What Causes It?
As many as 20,000 people develop AVN each year. Most are between ages 20 and 50. For healthy people, the risk of AVN is small. Most cases are the result of an underlying health problem or injury. Possible causes include:
Dislocation or fracture of the thigh bone (femur). This type of injury can affect the blood supply to the bone, leading to trauma-related avascular necrosis. AVN may develop in 20% or more of people who dislocate a hip.
Chronic corticosteroid use. Long-term use of these inflammation-fighting drugs, either orally or intravenously, is associated with 35% of all cases of nontraumatic AVN. Although the reason for this is not completely understood, doctors suspect these drugs may interfere with the body's ability to break down fatty substances. These substances collect in the blood vessels -- making them narrower -- and reduce the amount of blood to the bone.
Excessive alcohol use. Much like corticosteroids, excessive alcohol may cause fatty substances to build in the blood vessels and decrease the blood supply to the bones.
Other conditions associated with nontraumatic AVN include:
- Gaucher disease, an inherited metabolic disorder in which harmful quantities of a fatty substance accumulate in the organs
- Sickle cell disease
- Pancreatitis, inflammation of the pancreas
- HIV infection
- Radiation therapy or chemotherapy
- Autoimmune diseases
- Decompression sickness, a condition that occurs when the body is subjected to a sudden reduction in surrounding pressure, causing the formation of gas bubbles in the blood
Symptoms of Avascular Necrosis
In its early stages, AVN typically cause no symptoms; however, as the disease progresses it becomes painful. At first, you may experience pain when you put pressure on the affected bone. Then, pain may become more constant. If the disease progresses and the bone and surrounding joint collapse, you may experience severe pain that interferes with your ability to use your joint. The time between the first symptoms and collapse of the bone may range from several months to more than a year.
Treatment for Avascular Necrosis
The goals of treatment for AVN are to improve or ensure function of the affected joint, stop the progression of bone damage, and reduce pain.
The best treatment will depend on a number of factors, including:
- Your age
- Stage of the disease
- Location and amount of bone damage
- Cause of AVN
If the cause of your avascular necrosis is identified, treatment will include efforts to manage the underlying condition. For example, if AVN is caused by blood clots, your doctor will prescribe medications to dissolve clots. If inflammation of the arteries is responsible, your doctor may prescribe anti-inflammatory medicines.
If avascular necrosis is caught early, treatment may involve taking medications to relieve pain or limiting the use of the affected area. If your hip, knee, or ankle is affected, crutches may be necessary to take weight off the damaged joint. Your doctor may also recommend range-of-motion exercises to help keep the affected joint mobile.
While these nonsurgical treatments may slow the progression of avascular necrosis, most people with the condition eventually need surgery.
Surgical options include:
- Bone grafts, which involve removing healthy bone from one part of the body and using it to replace the damaged bone
- Osteotomy, a procedure that involves cutting the bone and changing its alignment to relieve stress on the bone or joint
- Total joint replacement, which involves removing the damaged joint and replacing it with a synthetic joint
- Core decompression, a procedure that involves removing part of the inside of the bone to relieve pressure and allow new blood vessels to form
- Vascularized bone graft, a procedure that uses the patient's own tissue to rebuild diseased or damaged hip joints; the surgeon first removes the bone with the poor blood supply from the hip and then replaces it with the blood-vessel-rich bone from another site, such as the fibula, the smaller bone located in the lower leg.