Avascular necrosis is a condition resulting from the loss of blood supply to bone. The most common cause of avascular necrosis, also known as osteonecrosis, is trauma.
Among other common causes are high dose corticosteroid ("cortisone") use, excessive alcohol, smoking, blood disorders such as sickle cell anemia, leukemia, exposure to chemotherapy drugs, radiation, elevated blood uric acid, HIV infection, transplantation, and others. One interesting cause is Caisson's disease, also known as "the bends" which occurs in divers and others who are exposed to rapid changes in atmospheric pressure.
Many classification systems, based on x-ray findings, have been used. While detection of early avascular necrosis is usually made by magnetic resonance imaging (MRI), the most accurate method of assessing damage is probably via arthroscopy (using a small telescope) to look at the area of suspected damage. The downside of this approach though, is the invasive nature of the procedure.
Treatment usually begins with non-operative treatments.
The first is limited weight-bearing using a cane, walker, or crutches. The theory is that limited weight-bearing may slow progression of disease.
While this treatment can be effective for mild cases where the amount of damage is small, it is generally not effective for more s3eevere disease.
A number of drug combinations have been used with varying success. One author reported on his experience using anti-inflammatory corticosteroids plus statin drugs. Another study suggests that stanozolol, an anabolic steroid (different from the anti-inflammatory steroids) might be effective. Iloprost, a medicine that opens up arteries has been reported to be effective, as has low molecular weight heparin.
Other drugs that have been tried include bisphosphonate drugs (drugs used to treat osteoporosis) and ACTH.
Hyperbaric oxygen and electromagnetic therapy has also been attempted.
All of the above have had varying amounts of success and the data is far from clear cut.
The treatment of choice for early avascular necrosis is core decompression. This is a procedure where a small hole is drilled into the head of the bone. The theory is that by relieving pressure within the bone marrow, there is restoration of normal blood flow. This procedure is usually combined with other things such as bone grafting or electrical stimulation.
Various growth factors such as bone morphogenic protein and angiogenesis (blood vessel growth) factors have also been reported on.
Interest in the use of bone marrow acquired stem cells has also increased recently.
Osteotomy- removal of a wedge of bone- to move the avascular and diseased portion of the bone- away from the weight bearing part of the joint is another therapy that has been used.
One new intervention that is being watched carefully is the use of a tantalum rod. This metallic rod is porous and is combined with growth factors to stimulate new bone growth around the rod.
For end stage disease, total joint replacement remains the standard of care. This is mandatory when both the cup as well as the head of the bone are involved.
Many factors are involved in determining what treatment to offer an individual patient. These include the severity of avascular necrosis, patient symptoms, health status, activity level, and life expectancy.
