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Avascular Necrosis

Avascular necrosis results from either temporary or permanent loss of blood to the bones. Although it can happen in any bone, the condition tends to affect the ends of long bones, such as the femur. Causes include injury or long-term use of steroid medicines or alcohol. As the disease progresses, symptoms can include joint pain, limited range of movement, and osteoarthritis.

What Is Avascular Necrosis?

Avascular necrosis is a disease resulting from the temporary or permanent loss of the blood supply to the bones. Without blood, the bone tissue dies and causes the bone to collapse. If the process involves the bones near a joint, it often leads to collapse of the joint surface.
 
Avascular necrosis is also known as:
 
  • Osteonecrosis
  • Aseptic necrosis
  • Ischemic bone necrosis.
     

Understanding Bone Rebuilding

The process of bone rebuilding takes place after an injury as well as during normal growth. Normally, bone continuously breaks down and rebuilds -- old bone is reabsorbed and replaced with new bone. The process keeps the skeleton strong and helps it to maintain a balance of minerals.
 
In the course of avascular necrosis, however, the healing process is usually ineffective and the bone tissues break down faster than the body can repair them. If left untreated, the condition progresses, the bone collapses, and the joint surface breaks down, leading to pain and arthritis.
 

What Bones Are Affected by Avascular Necrosis?

Although it can happen in any bone, avascular necrosis most commonly affects the ends (epiphyses) of long bones such as the femur -- the bone extending from the knee joint to the hip joint. Other common sites of avascular necrosis include:
 
  • Upper arm bone
  • Knees
  • Shoulders
  • Ankles.
     
The condition may affect just one bone, more than one bone at the same time, or more than one bone at different times.
 
Avascular necrosis usually affects men and women between 30 and 50 years of age. Depending on a person's risk factors and whether the underlying cause is trauma, it also can affect younger or older people. About 10,000 to 20,000 people develop avascular necrosis each year. Orthopedic doctors are the ones who usually diagnose the condition.
 

Causes of Avascular Necrosis

There are several causes of avascular necrosis. These causes can be separated as those related to trauma (trauma-related avascular necrosis) and causes not related to trauma (nontraumatic avascular necrosis). The two most common nontraumatic causes are steroid medicines and alcohol use.
 

Symptoms of Avascular Necrosis

Avascular necrosis symptoms vary based on the location and severity of the disease and whether the bone is a weight-bearing one.
 
In the early stages of the disease, people may not have any symptoms of avascular necrosis at all. As the condition progresses, however, symptoms can include:
 
Other health problems can also cause these symptoms, so anyone with possible symptoms of avascular necrosis should see a doctor. Only a doctor can diagnose and treat the problem.
 

Diagnosing Avascular Necrosis

In order to make an avascular necrosis diagnosis, the doctor will ask a number of questions, perform a physical exam, and recommend certain tests. Tests used to make a diagnosis, determine the amount of bone affected, and how far the disease has progressed include:
 
  • X-rays
  • Magnetic resonance imaging (MRI) scans
  • Bone scans
  • Computed tomography (CT) scans
  • Biopsy
  • Functional evaluation of bone.
     

Treatment for Avascular Necrosis

Several avascular necrosis treatment options are available that can help prevent further bone and joint damage and reduce pain.
 
The goals of treatment are:
 
  • Improve use of the affected joint
  • Stop further damage to the bone
  • Ensure bone and joint survival.
 
To reach these goals, the doctor may recommend one of several nonsurgical treatment options or surgery.
 

Effect of Avascular Necrosis

The amount of disability that results from avascular necrosis depends on what part of the bone is affected, how large an area is involved, and how effectively the bone rebuilds itself.
 
Appropriate treatment for avascular necrosis is necessary to keep joints from breaking down. If left untreated, most people will experience severe pain and limitation in movement within two years (see Avascular Necrosis Pain).
 
Written by/reviewed by: Arthur Schoenstadt, MD
Last reviewed by: Arthur Schoenstadt, MD
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