Avascular necrosis (AVN) is a bone condition caused by an inadequate blood supply to a section of bone that results in localized bone death. This condition may or may not cause pain, and its treatment depends on the stage of the condition.
Definition & Facts
Avascular necrosis (AVN), also known as aseptic necrosis or osteonecrosis is a death of the bone tissue following a lack of blood supply. The disease can cause tiny breaks in the bone, and finally, the bone may collapse. The blood flow to the bone may be interrupted by a bone fracture or dislocation. AVN eventually causes the destruction of the joint that is adjacent to the affected bone.
AVN is also associated with long-term use of medications that have a high dose of steroids, and excessive alcohol consumption. This malady can affect anyone, but most often it occurs in individuals aged between 30 and 60.
AVN can have significant long-term consequences for patients because it attacks at a young age. There are about 10,000 to 20,000 annual cases of AVN in the United States. The disease affects one in 27,000 individuals of the US population.
Symptoms & Complaints
The first sign of the condition is the pain in the affected area. If the lower extremity is affected, the disease can cause a limp when walking. If it has hit the hip, pain in the groin is common, especially when walking. As the hip ball collapses after the progression of the disease, hip pain can persist during weight-bearing or while walking. When necrosis affects the hips, the pain is often focused on the buttocks, groin or thighs. The other areas likely to be affected include the shoulder, hand, foot, and knee. Some people develop bilateral AVN, that is, it affects both knees or hips.
Osteonecrosis is caused by the impairment of blood supply to the bone, but the causes of the impairment are not clear. AVN often occurs in individuals with certain medical conditions or risk factors (such as excessive alcohol consumption or high-dose corticosteroid use). However, it also affects people without health problems, and for no known reasons.
Apart from injuries, the most common cause of AVN is the use of corticosteroid medications (such as prednisone). Corticosteroids are often used to treat inflammatory diseases such as vasculitis, severe asthma, systemic lupus erythematosus (SLE), inflammatory bowel syndrome, and rheumatoid arthritis. Studies show that long-term use of intravenous or oral corticosteroids is linked to non-traumatic avascular necrosis. Thus, patients should discuss the use of steroids with their doctors.
Doctors are not sure why the use of corticosteroids leads to AVN, but they speculate that the drug hampers the ability of the body to break down lipids (fatty substances). The lipids then build up and clog the blood vessels. When the blood vessel becomes narrow, it reduces the amount of blood getting to the bone.
Excessive alcohol consumption is also a common cause of AVN. Individuals who drink excess alcohol develop fatty substances that clog the blood vessels, which leads to a decreased blood supply to the bone.
When dislocation, fracture, or injury occur, the blood vessels are damaged. This tends to interfere with the blood supply to the bone, and it causes trauma-related osteonecrosis. Studies indicate that fractures and dislocation are significant risks for causing AVN.
Another cause of AVN is increased pressure within the bone, which causes a narrowing of the blood vessels and makes it difficult for them to deliver sufficient blood to the bone. Reasons for this pressure are not known.
Other risk factors for the disease include organ transplantation (especially kidney transplantation), chemotherapy, and radiation therapy. Also, medical conditions such as cancer, HIV, Caisson disease, SLE, sickle cell anemia, and Gaucher’s disease can cause the malady.
Diagnosis & Tests
During the physical exam, the doctor puts pressure on the joints to check for tenderness. The doctor will also move the joints to various positions to see if their range of motion has been affected. Imaging tests are also used to diagnose the disease. Many disorders can cause pain in the joints, and the imaging tests are thus used to pinpoint the source of pain. They include:
- X-rays—these are used to reveal changes in the bone that take place in later stages of osteonecrosis. In the early phases of the disease, X-rays often appear normal
- Bone scan—a small quantity of radioactive material known as a tracer is injected into the vein. The tracer travels to the parts of the bone that are injured or healing, and they appear as bright spots on the imaging plate
- MRIs and CT scan —these are tests done to provide detailed images that show early changes in the bone that may be an indication of aseptic necrosis
Treatment & Therapy
- Stage of disease
- Cause of AVN
- Location and extent of bone damage
If the origin of the disease is identified, the treatment is done to manage the underlying cause. For example, if it is caused by blood clots, the doctor will prescribe medications to dissolve the clots. If it is caused by inflammation in the arteries, the doctor will prescribe anti-inflammatory drugs.
If the disease is discovered early, the treatment is done by prescribing medications for the pain, and restricting the use of the affected joint. If the illness has affected the knee or hip, the patient is advised to use crutches to reduce weight on the affected joint. The doctor will also recommend exercise to increase the range of motion of the joint. These non-surgical treatments may slow the progression of AVN, but most people will eventually require surgery. The surgical options include:
- Bone grafting—removing a healthy bone from a different part of the body and replacing it with the damaged bone
- Total joint replacement—removing the damaged joint and inserting a synthetic joint
- Osteotomy—cutting the bone and altering its alignment to reduce stress on the joint or bone
- Core decompression—removing part of the inside of the bone to reduce its inner pressure and allow other blood vessels to form
- Vascularized bone graft—this technique uses the patient’s own tissue to recreate damaged or diseased hip joints. The surgery removes the bone with the poor blood supply, and a bone rich in blood supply from another site replaces it.
Prevention & Prophylaxis
- Limit alcohol—heavy drinking is among the top risk factors for AVN
- Keep cholesterol levels low—tiny particles of fat are the greatest culprits that cause blockage of blood vessels
- Monitor the use of steroids—the patient should inform the physician of any past and present use of high-dose steroids