Understanding Avascular Necrosis: Causes and Risk Factors

Avascular necrosis can affect the hip, knee, shoulder, hand, or foot. It may occur on one or both sides of the body. Often, people with the early stages of avascular necrosis experience no symptoms. As the disease advances, an individual may feel pain in the affected joint only when he puts weight on it. Eventually, the pain will persist even when laying down. It can range from mild to severe and occurs gradually.

If left untreated, avascular necrosis worsens with time, and the bone can eventually collapse. Additionally, avascular necrosis causes the bone to lose its smooth shape, which can lead to severe arthritis. To help prevent the complications of avascular necrosis, people with any pain in their joints should see a doctor, particularly if they suspect a break or dislocation.

In approximately 25% of cases of avascular necrosis, the cause of interrupted or reduced blood flow to the bone is unknown. In other cases, bone or joint trauma may be the cause. For instance, a dislocated joint, can damage the blood vessels nearby.

Cancer treatments using radiation can damage blood vessels and weaken bones. Gaucher's disease and sickle cell anemia can also cause diminished blood flow to bones. Blood flow is also reduced if lipids or fats are deposited in small blood vessels.

Several factors can put an individual at risk for developing avascular necrosis. In addition to those potential causes noted above, excessive alcohol use can put an individual at risk, as well, because it leads to fatty deposits developing in blood vessels.

Another common cause of avascular necrosis is long-term use of steroids in high doses. The long-term use of bisphosphonates, medications used to increase bone density, can also lead to the condition.

Radiation therapy and organ transplantation, especially kidney transplants, are also related to avascular necrosis. Medical conditions such as sickle cell anemia, pancreatitis, systemic lupus erythematosus, diabetes, and HIV/AIDS can cause the condition, as well.

When someone visits his doctor with concerns about his joints, the doctor will do a physical exam to check for tenderness and range of motion. Imaging tests are useful in the diagnosis of avascular necrosis. X-rays can show the bone changes that take place in the later stages of avascular necrosis. MRIs can produce more detailed images of bone, revealing early changes that may help diagnose the condition more quickly. Bone scans require the doctor inject a small amount of radioactive material into the vein. The material travels to parts of the bone that are either healing or injured, showing up as bright spots on an imaging plate.

People with avascular necrosis can slow the progression of their condition by making certain lifestyle changes. Resting the affected joint by keeping weight off of it can slow the damage. Some people may need to restrict physical activities and use crutches for several months. Also, a physical therapist can teach patients exercises to help maintain or improve range of motion. Over-the-counter NSAIDs can help relieve the pain associated with this condition.

Several medical treatment options exist for individuals with avascular necrosis.

• Medications used to treat osteoporosis may slow the progression of avascular necrosis.
• Doctors may recommend blood thinners to individuals who have clotting problems, to keep blood clots from developing in blood vessels that feed bones.
• Decreasing the amount of fat and cholesterol in the blood , through medications or lifestyle changes, may help prevent blood vessel obstruction that can lead to avascular necrosis.
• Electrical stimulation can encourage the body to grow new bone to replace damaged bone. A specialist can apply the machine directly to the damaged bone during surgery, or attach electrodes to the skin.

Some people may require surgery to treat the advanced stages of avascular necrosis.

• Core Decompression: The surgeon removes part of the inner layer of bone. This not only relieves pain, but it also encourages the body to create new bone and blood vessels.
• Bone Reshaping (Osteotomy): To shift weight off of a damaged joint, the surgeon removes a wedge of bone above or below the joint. This may help postpone joint replacement surgery.
• Bone Transplant (Graft): The surgeon adds part of a bone taken from somewhere else in the body to the affected joint to help strengthen it.
• Joint Replacement: Plastic or metal parts can replace damaged areas of the affected joint.

Limiting alcohol intake can reduce the risk of avascular necrosis, as can quitting smoking. The most common substance obstructing blood flow to bones are little bits of fat, so keeping cholesterol levels low helps prevent these deposits and lowers the risk of developing the condition.