Avascular Necrosis: When Bone Dies

When bone tissue doesn't receive enough blood, it can die. This condition is called "avascular necrosis" or "osteonecrosis." Avascular bone necrosis can lead to tiny breaks in the bone, causing it to eventually collapse if not treated properly. While rare, avascular necrosis of the spine can occur (also referred to as "Kummel's Disease" or "vertebral osteonectosis.")

Avascular Bone Necrosis: Causes

Although scientists are still trying to determine the actual causes of avascular bone necrosis, some factors have been identified that may interrupt blood flow to bone:

• Excessive alcohol use: High levels of alcohol can produce fatty substances that block blood vessels.
• Joint injury: Bone fractures or joint dislocation may damage or destroy nearby blood vessels.
• Long-term use of high-dose steroid medications: Approximately 35 percent of avascular necrosis cases are due to long-term steroid use, according to researchers at Penn State University.
• Narrowed blood vessels: A tiny piece of fat may clog a blood vessel, or clumps of deformed blood cells may clog blood vessels in the case of sickle cell anemia.
• Pressure inside the bone: Increased pressure inside a bone is most likely caused by another medical condition or a medical treatment.

Avascular Necrosis Symptoms

Although the most common symptoms of bone necrosis are pain and reduced range of motion in the affected joint, some people may experience no symptoms at all. Symptoms may also appear suddenly if caused by an injury, or the pain and stiffness may build up slowly over several months.

Although bone necrosis can occur in many different bones or joints, the most common type is avascular hip necrosis, also known as femoral avascular necrosis. In avascular hip necrosis, the top of the head of the femur (thigh bone), which forms the hip joint, collapses and begins to flatten. This type of bone necrosis may cause pain in the hip joint, as well as in the groin or down the thigh to the knee.

The other two joints most commonly affected by avascular necrosis are the:

• Knee (usually with pain on the inner knee that worsens during activity)
• Shoulder (usually in the upper arm bone).

Avascular Bone Necrosis Treatment

Avascular necrosis treatment aims to prevent more bone loss, and treatment methods depend on the amount of bone damage already present. In the early stage, medications and therapy are the most common treatments.

Medications used to treat bone necrosis include:

• Bisphosphonates (Some studies indicate that osteoporosis medications may slow down the progress of avascular necrosis.)
• Blood thinners for people with clotting disorders
• Cholesterol-lowering medications for people with clogged blood vessels
• Non-steroidal anti-inflammatory drugs (NSAIDs) for those experiencing pain and inflammation.

Therapy methods may include:

• Electrical stimulation to promote bone growth
• Motion exercises to keep the joints mobile
• Rest and reduced weight bearing to take the stress off affected bone.

Avascular necrosis worsens with time, so managing it is a lifelong process. According to the National Institute of Arthritis and Musculoskeletal and Skin Diseases, most sufferers will eventually require surgery. Surgical options include:

• Bone graft: The transplantation of healthy bone from another part of the body.
• Core decompression: Removal of the inner cylinder of the bone, which reduces pressure within the bone, increases blood flow to the bone and lets more blood vessels form. Core decompression is mostly recommended during the early stages of bone necrosis.
• Osteotomy: Reshaping of the bone to reduce stress on the affected area.
• Total joint replacement: Often necessary in late-stage avascular necrosis and when the joint is destroyed.

Resources

Mayo Clinic Staff. (n.d.). Avascular necrosis. Retrieved March 26, 2010, from http://www.mayoclinic.com/health/avascular-necrosis/DS00650

Milton S. Hershey College of Medicine Staff. (2010). Avascular necrosis. Retrieved April 12, 2010, from http://www.hmc.psu.edu/healthinfo/a/avascularnec.htm

National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) Staff. (2009). Osteonecrosis. Retrieved March 26, 2010, from http://www.niams.nih.gov/Health_Info/Osteonecrosis/default.asp

Aiello, M. R. (2009). Avascular necrosis, femoral head. Retrieved March 26, 2010, from http://emedicine.medscape.com/article/386808-overview