Aseptic Necrosis (Osteonecrosis or Avascular Necrosis)

Aseptic necrosis is a bone condition that results from poor blood supply to an area of bone, causing localized bone death. This is a serious condition because the dead areas of bone do not function normally, are weakened, and can collapse. Aseptic necrosis is also referred to as avascular necrosis or osteonecrosis.

Aseptic necrosis can be caused by trauma and damage to the blood vessels that supply bone oxygen.

Other causes of poor blood circulation to the bone include a blockage by air or fat (embolism) that obstructs the blood flow through the blood vessels, abnormally thick blood (hypercoagulable state), atherosclerosis (hardening of the arteries), or inflammation of the blood vessel walls (vasculitis).

Steroid medications (cortisone, such as prednisone [Deltasone, Liquid Pred] and methylprednisolone [Medrol, Depo-Medrol]) are the most common medications to cause aseptic necrosis. Typical bones affected by steroids include the femur bone of the hip, the humerus bone of the shoulder, and the tibia bone of the knee, sometimes in combinations and frequently affecting both sides of the body (bilateral). Aseptic necrosis of the jawbone has been associated with the use of medications (bisphosphonates) used to treat high blood calcium levels from cancer.

Conditions that are risk factors associated with aseptic necrosis include:

• Alcoholism
• Cortisone medications
• Cushing's syndrome
• Radiation exposure
• Smoking cigarettes
• Sickle cell disease
• Pancreatitis
• Hyperlipidemia
• Caisson's disease (dysbarism)
• Gaucher disease
• Systemic lupus erythematosus

Aseptic necrosis of the jawbone has been rarely reported in association with the use of bisphosphonate medication, particularly intravenously including zoledronate (Zometa) and pamidronate (Aredia).

Aseptic necrosis begins as a painless bone abnormality. It can remain painless. The involved bone often later develops pain, especially with use.

For example, if a hip joint develops avascular necrosis in the ball of the hip joint, pain can be noted, especially upon weight-bearing. As the ball of the hip joint collapses from the degeneration of the bone from aseptic necrosis, pain in the groin can be felt with hip rotation and pain can sometimes be noted with rest after weight-bearing.

• Aseptic necrosis of the knee is often associated with pain or limping with walking.
• Aseptic necrosis of the shoulder can be associated with pain and loss of range of motion of the shoulder joint.

The diagnosis of aseptic necrosis can often, but not always, be made with plain film X-rays. By the time changes are apparent by plain film X-ray testing there has been substantial damage to the bone affected. Bone changes visible on plain film X-ray are, therefore, considered a later-stage finding.

Earlier signs of avascular necrosis can be detected with an MRI scan image or suggested by a nuclear bone scan image.

The treatment of aseptic necrosis is critically dependent on the stage of the condition. Very early-stage aseptic necrosis may be managed nonoperatively with rest, partial-weight-bearing crutches, progressive weight-bearing, and observation. Nevertheless, there is often a progression of joint damage.

Early aseptic necrosis (before X-ray image changes are evident) can be treated with a core decompression surgical operation. This procedure involves removing a core of bone from the involved area and sometimes grafting new bone into the area. This allows the new blood supply to form, preserving the bone. Weight-bearing or impact of the involved joint is restricted.

Later stages of aseptic necrosis (when X-ray image changes are apparent) typically lead to seriously damaged bone and joints, requiring joint replacement surgery.

Aseptic necrosis causes serious injury to the affected bone. Frequently, this leads to the permanent destruction of the adjacent joint. Early core decompression is generally necessary to prevent the collapse of the affected bone. Aseptic necrosis can be complicated by complete loss of joint function.

People can prevent aseptic necrosis by minimizing steroid medications when possible and treating underlying medical conditions, such as those described above, that can increase the risk of developing aseptic necrosis. Avoiding trauma to joints can prevent posttraumatic aseptic necrosis. Avoiding smoking can decrease the risk of developing aseptic necrosis.