Avascular necrosis

Avascular necrosis of the hip is the death of bone tissue in the hip joint due to an inadequate blood supply. This loss of blood supply can cause tiny breaks in the bone and, eventually, the bone's collapse.

If avascular necrosis is unidentified and uncorrected, it will progress to a deformity and lead to pain and a limp.

Causes

Avascular necrosis of the hip can occur when blood flow to a bone is reduced or blocked. Each year in the United States, about 10,000-20,000 people are diagnosed with avascular necrosis. They are predominantly males, typically under 40 years old.

Some causes of reduced blood flow to a bone include:

• Injury to the bone or joint, such as dislocation
• Radiation therapy, which can damage blood vessels
• Conditions that increase pressure inside the bone, such as sickle cell anemia

Risk Factors

Although the cause of avascular necrosis isn't fully understood, several risk factors that increase your likelihood of getting the disease have been identified. If you have any of these risk factors, be sure to discuss them with your physician:

• Femoral neck fractures
• Dislocation of the hip
• Radiation therapy
• Prolonged or repeated use of steroid medications
• Decompression sickness
• Sickle cell disease
• Gaucher's disease
• Excessive alcohol use
• Systemic lupus erythematous (SLE)
• Renal transplantation
• HIV infection

Symptoms

Avascular necrosis often develops gradually. The earliest symptoms are nonspecific and may be caused by other, less serious health conditions.

• Groin pain is the most common symptom, especially with weight-bearing activities
• Buttock, thigh and knee pain
• Limping

Diagnosis

Your doctor will ask about your symptoms and medical history and perform a physical exam, checking the joint's range of motion and tenderness. Imaging tests will also be ordered to get a better look at the bones and help make a conclusive diagnosis

Test may include the following:

• X-ray. X-rays can provide a clear view of the bones. However, when avascular necrosis is seen on the X-ray, it is usually too advanced to be reversed with treatment.
• CT scan. This type of X-ray uses a computer to take pictures of structures inside the body.
• Radioisotope bone scan. In bone scans, radioactive material is injected into the veins. This material travels to bones that are healing or injured so they can be viewed.
• MRI scan. This test uses magnetic waves to make pictures of structures inside the body. This is the most useful test and can detect the condition early enough to begin effective treatment.

Treatment

Your physician will work with you to develop a treatment plan, which will depend on the stage of the disease and your lifestyle. Treatment options include the following:

Conservative treatment

Treating avascular necrosis conservatively may delay the need for surgery in some patients.

Taking nonsteroidal anti-inflammatory drugs (NSAIDs) and other pain relievers can help alleviate symptoms. Performing non-weight-bearing exercises, such as swimming or cycling, may prevent or minimize the progression of the disease.

Surgery

In the long-term, surgery to treat avascular necrosis may become necessary for most patients.

There are several surgical procedures used; the method depends upon the extent of disease and the age and health status of the patient. Bone grafts, decompression of the inside of the bone, realignment of the bone and prosthetic hip replacement are all available options.

Prevention

To help reduce your chances of getting avascular necrosis of the hip, take the following steps:

• Avoid injury, particularly bone fractures and joint dislocation
• Keep the dosage and duration of cortisone-like drugs to a minimum
• Avoid decompression disease when diving underwater

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