Avascular Necrosis: What is it?

What Causes Avascular Necrosis?

Alcohol Use and Corticosteroid Use

Avascular necrosis has several causes. Loss of blood supply to the bone can be caused by an injury (trauma-related avascular necrosis) or by certain risk factors (non-traumatic avascular necrosis), such as some medications (steroids) or excessive alcohol use. Increased pressure within the bone also is associated with avascular necrosis. The pressure within the bone causes the blood vessels to narrow, making it hard for the vessels to deliver enough blood to the bone cells.

Excessive alcohol use and corticosteroid use are two of the most common causes of non-traumatic avascular necrosis. In people who drink an excessive amount of alcohol, fatty substances may block blood vessels causing a decreased blood supply to the bones that results in avascular necrosis.

How Is Avascular Necrosis Diagnosed?

Biopsy

A biopsy is a surgical procedure in which tissue from the affected bone is removed and studied. Although a biopsy is a conclusive way to diagnose avascular necrosis, it is rarely used because it requires surgery.

The goal in treating avascular necrosis is to improve the patient's use of the affected joint, stop further damage to the bone, and ensure bone and joint survival. To reach these goals, the doctor may use one or more of the following treatments:

Bone Graft

A bone graft may be used to support a joint after core decompression. Bone grafting is surgery that transplants healthy bone from one part of the patient, such as the leg, to the diseased area. There is a lengthy recovery period after a bone graft, usually from 6 to 12 months. This procedure is complex and its effectiveness is not yet proven. Clinical studies are under way to determine its effectiveness.

Bone Scan

Also known as bone scintigraphy, bone scans are used most commonly in patients who have normal x rays. A harmless radioactive dye is injected into the affected bone and a picture of the bone is taken with a special camera. The picture shows how the dye travels through the bone and where normal bone formation is occurring. A single bone scan finds all areas in the body that are affected, thus reducing the need to expose the patient to more radiation. Bone scans do not detect avascular necrosis at the earliest stages.

Computed/Computerized Tomography

A CT scan is an imaging technique that provides the doctor with a three-dimensional picture of the bone. It also shows "slices" of the bone, making the picture much clearer than x rays and bone scans. Some doctors disagree about the usefulness of this test to diagnose avascular necrosis. Although a diagnosis usually can be made without a CT scan, the technique may be useful in determining the extent of bone damage.

Functional Evaluation of Bone

Tests to measure the pressure inside a bone may be used when the doctor strongly suspects that a patient has avascular necrosis, despite normal results of x rays, bone scans, and MRIs. These tests are very sensitive for detecting increased pressure within the bone, but they require surgery.

How Is Avascular Necrosis Treated?

The goal in treating avascular necrosis is to improve the patient's use of the affected joint, stop further damage to the bone, and ensure bone and joint survival. To reach these goals, the doctor may use one or more of the following treatments:

Core Decompression

This surgical procedure removes the inner layer of bone, which reduces pressure within the bone, increases blood flow to the bone, and allows more blood vessels to form. Core decompression works best in people who are in the earliest stages of avascular necrosis, often before the collapse of the joint. This procedure sometimes can reduce pain and slow the progression of bone and joint destruction in these patients.

In addition to the above treatment, doctors are exploring the use of medications, electrical stimulation, and combination therapies to increase the growth of new bone and blood vessels. These treatments have been used experimentally alone and in combination with other treatments, such as osteotomy and core decompression.

For most people with avascular necrosis, treatment is an ongoing process. Doctors may first recommend the least complex and invasive procedure, such as protecting the joint by limiting movement, and watch the effect on the patient's condition. Other treatments then may be used to prevent further bone destruction and reduce pain. It is important that patients carefully follow instructions about activity limitations and work closely with their doctors to ensure that appropriate treatments are used.

Updated on: 09/11/12
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Avascular Necrosis: Risk Factors, Diagnosis and Treatment
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Avascular Necrosis: Risk Factors, Diagnosis and Treatment

The goal in treating avascular necrosis is to improve the patient's use of the affected joint, stop further damage to the bone, and ensure bone and joint survival.
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