Avascular Necrosis: An Introduction
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 and Avascular Necrosis
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, avascular necrosis 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.
Avascular necrosis 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 avascular necrosis.
Causes of Avascular Necrosis
There are several
causes of avascular necrosis. These causes can be separated as causes related to trauma (trauma-related avascular necrosis) and causes not related to trauma (nontraumatic avascular necrosis). The two most common nontraumatic causes of avascular necrosis are steroid medicines and alcohol use.
Symptoms of Avascular Necrosis
Avascular necrosis symptoms vary based on the location and severity of avascular necrosis and whether the bone is a weight-bearing one.
In the early stages of the disease, patients may not have any symptoms of avascular necrosis. 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 diagnose avascular necrosis, 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
The goals of treatment for avascular necrosis 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 avascular necrosis treatment is necessary to keep joints from breaking down. If left untreated, most patients will experience severe pain and limitation in movement within 2 years.
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