Osteonecrosis

Osteonecrosis, which is also called avascular necrosis (AVN) or aseptic necrosis, is the death of bone cells due to decreased blood flow. It can lead to pain and collapse of areas of bone. This collapse of bone, in turn, can lead to degenerative arthritis (also called osteoarthritis) of nearby joints, most often the hips and knees. Less often affected spots are the shoulders, hands and feet. Rarely, osteonecrosis can occur in the jaw. This can result in ulcers (sores) of gum tissue, exposed jawbone and pain.

The most common causes of osteonecrosis are:

• Serious trauma (injury), which interrupts a bone’s blood supply
• Corticosteroid medications (such as prednisone, cortisone or methylprednisolone), mainly when a high dose is used for a prolonged period of time
• Excess alcohol consumption
• Systemic lupus erythematosus

Other less common risk factors for osteonecrosis include:

• Decompression disease (also called the “Bends” that can occur with scuba diving)
• Blood disorders such as sickle cell anemia, antiphospholipid antibody syndrome (APS) and lupus anticoagulant
• HIV infection (the virus that causes AIDS)
• Radiation therapy
• Bisphosphonates
• Organ transplants

Most of the 10,000 to 20,000 Americans who develop osteonecrosis each year are between the ages of 20 and 50. These people most often have a history of serious trauma, corticosteroid use, excess alcohol intake or one of the other risk factors listed in “What causes osteonecrosis?”

Doctors suspect osteonecrosis when a person with risk factors for it feels bone pain that is “localized” (limited to a small area). Patients with hip pain due to osteonecrosis often feel pain in the groin. Pain due to hip or knee osteonecrosis is most often worse with weight-bearing or walking.

The next step in diagnosis is to get an X-ray of the painful area. Because these X-rays may look normal in the early stages of disease, your doctor may schedule other imaging studies. These include bone scans or magnetic resonance images (often referred to as MRIs). MRI is excellent at helping detect very early osteonecrosis.

Unfortunately, there is no clear proof showing the best way to treat osteonecrosis but starting treatment early—before collapse of bone—is best.

Early treatment
Often, treatment starts with pain medications and by limiting weight-bearing (such as walking) on affected areas. This type of conservative treatment may work well for patients with early osteonecrosis in small areas of bone. Yet, it does not work for those with hip or knee osteonecrosis who are facing worsening disease and bone collapse. Instead, these patients may need surgical procedures to relieve pain and try to prevent bone collapse.

Surgery
Patients whose osteonecrosis is getting worse may need a procedure called core decompression. It removes a piece (core) of bone from the affected area, to try to improve blood flow.

More advanced cases may need a procedure called osteotomy. During this operation, surgeons remove dead bone and re-position the remaining bone so that healthy bone supports the weight-bearing joint surface. If bone collapse at the joint has already occurred, these patients often need total joint replacement (arthroplasty) of the hip or knee. This operation should improve pain and function.

Another surgery option for advanced cases is bone grafting. This involves taking a small piece of a person’s own healthy leg bone and grafting (transplanting) it to the area of dead bone. Bone grafting improves blood flow and support of the surrounding bone.

Medicine
There is no proven medical therapy for osteonecrosis. Some studies suggest that short-term bisphosphonate treatment may slow, improve or even prevent bone collapse in the hip and knee.

The key ways to prevent osteonecrosis are to avoid too much alcohol intake and avoid tobacco use, as smoking also raises the risk of osteonecrosis. Also, if you have to take corticosteroids, such as prednisone, work with your doctor to take the smallest dose for the shortest time possible that will control your symptoms.

Some people will develop osteoarthritis (also called degenerative arthritis or “wear and tear” of the joints) as a result of osteonecrosis. Working with a physical therapist on an exercise program may be helpful in treating the pain and stiffness from osteoarthritis.