What is osteonecrosis or AVN?

    Osteonecrosis occurs when your bones lose their blood supply. The bones die and eventually collapse, leading to pain and arthritis. You can have osteonecrosis in one or several bones. It is most common in the upper leg. Other common sites are your upper arm and your knees, shoulders and ankles. The disease can affect men and women of any age, but it usually strikes in your thirties, forties or fifties.


    Why people developed AVN?

    There are many causes of AVN. Anything that damages the blood supply to the hip can cause AVN.

    * Injury to the hip itself can damage the blood vessels. Fractures of the femoral neck bone can damage the blood vessels.

    * A dislocation of the hip out of the socket can tear the blood vessels.

    * Corticosteroids such as prednisone or methylprednisolone are the most common drugs known to lead to AVN.

    * Smoking causes blood vessels to constrict or narrow thereby limiting the amount of blood flow to an area such as the hip with its already limited backup supply.

    * Excessive alcohol intake somehow damages the blood vessels and leads to AVN.

    * Deep sea divers and miners who work under great atmospheric pressures also are at risk for damage to the blood vessels.

    * Then there is a long list of other diseases that are associated with increased incidence of femoral head osteonecrosis. Examples of these diseases are leukemia, sickle cell diseases, and HIV infection.


    What joints can be affected by AVN?

    The most common joints affected by AVN include:

    * Hip.

    * Knee.

    * Shoulder.


    Other joints that are less commonly affected by AVN include:

    Ankles, Feet, Hands, Jaw, Spine and Wrists.


    How is AVN diagnosed?

    Once there is a suspicion of osteonecrosis, your physician will likely obtain one or more of the following tests: X-ray, Magnetic Resonance Imaging (MRI), Bone Scan, Computed Tomography (CT), or rarely Biopsy.


    What are the treatment options for AVN?


    (A) Non-Surgical Treatment

    *  Protected weight bearing: Canes, crutches or a walker are useful in alleviating the pain associated with AVN.

    (B) Pharmaceutical Treatment

    *  There are no established drugs for the prevention or treatment of osteonecrosis.

    (C) Surgical Treatment

    * Core Decompression: This is a surgical procedure that involves taking a plug of bone out of the involved area. It is applicable for mild to moderate degree of involvement that has not yet progressed to collapse.

    * Bone Grafting: When a section of the bone has died, it does not spontaneously heal. One approach to this problem is to surgically remove the dead bone and fill the empty space with bone graft that is either taken from the patient or from the bone bank.

    * Osteotomy (Cutting the Bone): Usually the location of the AVN is in the area of the bone that bears weight. In some cases the bone can be cut below the area of involvement and rotated or turned so that another portion of the bone can become the new weight-bearing area.

    * Femoral Head Resurfacing: This involves implanting a metal hemisphere over the femoral head, which exactly matches the size of the original femoral head.

    * Femoral Head Replacement: This is basically half a total hip replacement.


    How I can prevent AVN?

    * To minimize the risk of AVN caused by corticosteroids, doctors use these drugs only when essential, prescribe them in as low a dose as needed, and prescribe them for as short duration as possible.

    * To prevent osteonecrosis caused by decompression sickness, people should follow accepted rules for decompression during diving and when working in pressurized environments.

    * Excessive alcohol use and smoking should be avoided.



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