National Institute of Arthritis and
Musculoskeletal and Skin Diseases
QUESTIONS AND ANSWERS ABOUT AVASCULAR NECROSIS
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. This disease also is known as osteonecrosis, aseptic
necrosis, and ischemic bone necrosis.
Although it can happen in any bone, avascular necrosis most
commonly affects the ends (epiphysis) of long bones such as the
femur, the bone extending from the knee joint to the hip joint. The
disease 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 people between 30 and 50 years of age; about 10,000
to 20,000 people develop avascular necrosis each year.
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. The process
of bone rebuilding takes place after an injury as well as during
normal growth. Normally, bone continuously breaks down and
rebuildsold bone is torn away and 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
disease progresses, the bone collapses, and the joint surface breaks
down, leading to pain and arthritis.
What Causes Avascular Necrosis?
Avascular necrosis has several causes. Loss of blood supply to the
bone can be caused by an injury (trauma-related avascular necrosis)
or by certain risk factors (non-traumatic avascular necrosis), such
as some medications (steroids) or excessive alcohol use. Increased
pressure within the bone also is associated with avascular necrosis.
The pressure within the bone causes the blood vessels to narrow,
making it hard for the vessels to deliver enough blood to the bone
cells.
Injury
When a joint is injured, as in a fracture or dislocation, the
blood vessels may be damaged. This can interfere with the blood
circulation to the bone and lead to trauma-related avascular
necrosis. Studies suggest that this type of avascular necrosis may
develop in more than 20 percent of people who dislocate their hip
joint.
Steroid Medications
Corticosteroids such as prednisone are commonly used to treat
diseases in which there is inflammation, such as systemic lupus
erythematosus, rheumatoid arthritis, and vasculitis. Studies suggest
that long-term, systemic (oral or intravenous) corticosteroid use is
associated with 35 percent of all cases of non-traumatic avascular
necrosis. However, there is no known risk of avascular necrosis
associated with the limited use of steroids. Patients should discuss
concerns about steroid use with their doctor.
Doctors arent sure exactly why the use of corticosteroids
sometimes lead to avascular necrosis. They may interfere with the
bodys ability to break down fatty substances. These substances then
build up in and clog the blood vessels, causing them to narrow. This
reduces the amount of blood that gets to the bone. Some studies
suggest that corticosteroid-related avascular necrosis is more severe
and more likely to affect both hips (when occurring in the hip) than
avascular necrosis resulting from other causes.
Alcohol Use
Excessive alcohol use and corticosteroid use are two of the most
common causes of non- traumatic avascular necrosis. In people who
drink an excessive amount of alcohol, fatty substances may block
blood vessels causing a decreased blood supply to the bones that
results in avascular necrosis.
Other Risk Factors
Other risk factors or conditions associated with non-traumatic
avascular necrosis include Gauchers disease, pancreatitis, radiation
treatments and chemotherapy, decompression disease, and blood
disorders such as sickle cell disease.
Who Is Likely To Develop Avascular
Necrosis?
Avascular necrosis strikes both men and women and affects people
of all ages. It is most common among people in their thirties and
forties. Depending on a persons risk factors and whether the
underlying cause is trauma, it also can affect younger or older
people.
What Are the Symptoms?
In the early stages of avascular necrosis, patients may not have
any symptoms. As the disease progresses, however, most patients
experience joint painat first, only when putting weight on the
affected joint, and then even when resting. Pain usually develops
gradually and may be mild or severe. If avascular necrosis progresses
and the bone and surrounding joint surface collapses, pain may
develop or increase dramatically. Pain may be severe enough to limit
the patients range of motion in the affected joint. The period of
time between the first symptoms and loss of joint function is
different for each patient, ranging from several months to more than
a year.
How Is Avascular Necrosis Diagnosed?
After performing a complete physical examination and asking about
the patients medical history (for example, what health problems the
patient has had and for how long), the doctor may use one or more
imaging techniques to diagnose avascular necrosis. As with many other
diseases, early diagnosis increases the chances of treatment success.
It is likely that the doctor first will recommend a radiograph,
commonly called an x ray. X rays can help identify many causes of
joint pain, such as a fracture or arthritis. If the x ray is normal,
the patient may need to have more tests. Research studies have shown
that magnetic resonance imaging, or MRI, is the most sensitive method
for diagnosing avascular necrosis in the early stages. The tests
described below may be used to determine the amount of bone affected
and how far the disease has progressed.
X Ray
An x ray is a common tool that the doctor may use to help diagnose
the cause of joint pain. It is a simple way to produce pictures of
bones. The x ray of a person with early avascular necrosis is likely
to be normal because x rays are not sensitive enough to detect the
bone changes in the early stages of the disease. X rays can show bone
damage in the later stages, and once the diagnosis is made, they are
often used to monitor the course of the condition.
Magnetic Resonance Imaging (MRI)
MRI is quickly becoming a common method for diagnosing avascular
necrosis. Unlike x rays, bone scans, and CT (computed/computerized
tomography) scans, MRI detects chemical changes in the bone marrow
and can show avascular necrosis in i ts earliest stages. MRI provides
the doctor with a picture of the area affected and the bone
rebuilding process. In addition, MRI may show diseased areas that are
not yet causing any symptoms.
Bone Scan
Also known as bone scintigraphy, bone scans are used most commonly
in patients who have normal x rays. A harmless radioactive dye is
injected into the affected bone and a picture of the bone is taken
with a special camera. The picture shows how the dye travels through
the bone and where normal bone formation is occurring. A single bone
scan finds all areas in the body that are affected, thus reducing the
need to expose the patient to more radiation. Bone scans do not
detect avascular necrosis at the earliest stages.
Computed/Computerized Tomography
A CT scan is an imaging technique that provides the doctor with a
three-dimensional picture of the bone. It also shows slices of the
bone, making the picture much clearer than x rays and bone scans.
Some doctors disagree about the usefulness of this test to diagnose
avascular necrosis. Although a diagnosis usually can be made without
a CT scan, the technique may be useful in determining the extent of
bone damage.
Biopsy
A biopsy is a surgical procedure in which tissue from the affected
bone is removed and studied. Although a biopsy is a conclusive way to
diagnose avascular necrosis, it is rarely used because it requires
surgery.
Functional Evaluation of Bone
Tests to measure the pressure inside a bone may be used when the
doctor strongly suspects that a patient has avascular necrosis,
despite normal results of x rays, bone scans, and MRIs. These tests
are very sensitive for detecting increased pressure within the bone,
but they require surgery.
What Treatments Are Available?
Appropriate treatment for avascular necrosis is necessary to keep
joints from breaking down. If untreated, most patients will suffer
severe pain and limitation in movement within 2 years.
Several treatments are available that can help prevent further
bone and joint damage and reduce pain. To determine the most
appropriate treatment, the doctor considers the following aspects of
a patients disease:
- The age of the patient.
- The stage of the diseaseearly or late.
- The location and amount of bone affecteda small or large
area.
- The underlying cause of avascular necrosiswith an ongoing
cause such as corticosteroid or alcohol use, treatment may not
work unless use of the substance is stopped.
The goal in treating avascular necrosis is to improve the
patients use of the affected joint, stop further damage to the bone,
and ensure bone and joint survival. To reach these goals, the doctor
may use one or more of the following treatments:
- Reduced Weight BearingIf avascular necrosis is
diagnosed early, the doctor may begin treatment by having the
patient remove weight from the affected joint. The doctor may
recommend limiting activities or using crutches. In some cases,
reduced weight bearing can slow the damage caused by avascular
necrosis and permit natural healing. When combined with medication
to reduce pain, reduced weight bearing can be an effective way to
avoid or delay surgery for some patients. Most patients eventually
will need surgery, however, to repair the joint permanently.
- Core DecompressionThis surgical procedure removes the
inner layer of bone, which reduces pressure within the bone,
increases blood flow to the bone, and allows more blood vessels to
form. Core decompression works best in people who are in the
earliest stages of avascular necrosis, often before the collapse
of the joint. This procedure sometimes can reduce pain and slow
the progression of bone and joint destruction in these
patients.
- OsteotomyThis surgical procedure reshapes the bone to
reduce stress on the affected area. There is a lengthy recovery
period, and the patients activities are very limited for 3 to 12
months after an osteotomy. This procedure is most effective for
patients with advanced avascular necrosis and those with a large
area of affected bone.
- Bone GraftA bone graft may be used to support a joint
after core decompression. Bone grafting is surgery that
transplants healthy bone from one part of the patient, such as the
leg, to the diseased area. There is a lengthy recovery period
after a bone graft, usually from 6 to 12 months. This procedure is
complex and its effectiveness is not yet proven. Clinical studies
are under way to determine its effectiveness.
- Arthroplasty/Total Joint ReplacementTotal joint
replacement is the treatment of choice in late-stage avascular
necrosis and when the joint is destroyed. In this surgery, the
diseased joint is replaced with artificial parts. It may be
recommended for people who are not good candidates for other
treatments, such as patients who do not do well with repeated
attempts to preserve the joint. Various types of replacements are
available, and people should discuss specific needs with their
doctor.
In addition to the above treatments, doctors are exploring the use
of medications, electrical stimulation, and combination therapies to
increase the growth of new bone and blood vessels. These treatments
have been used experimentally alone and in combination with other
treatments, such as osteotomy and core decompression.
For most people with avascular necrosis, treatment is an ongoing
process. Doctors may first recommend the least complex and invasive
procedure, such as protecting the joint by limiting movement, and
watch the effect on the patients condition. Other treatments then
may be used to prevent further bone destruction and reduce pain. It
is important that patients carefully follow instructions about
activity limitations and work closely with their doctors to ensure
that appropriate treatments are used.
What Research Is Being Done To Help People With
Avascular Necrosis?
With proper treatment, most people with avascular necrosis can
lead normal lives. But there is still a lot to learn about
prevention, diagnosis, and treatment. For example, researchers are
studying:
- New ways to diagnose avascular necrosis in its earliest
stages, when non- surgical treatment is most likely to help.
- The various causes of avascular necrosis so that, someday, it
may be possible to prevent the disease.
- New treatments and improvement of the treatments that are
available. In the future, medication may be an effective treatment
for avascular necrosis.
- Improvements to the various types of hip replacements, to
prevent younger patients from needing more than one hip
replacement during their life.
Where Can People Find More Information About
Avascular Necrosis?
Arthritis Foundation
1330 West Peachtree Street
Atlanta, GA 30309
404/872-7100
800/283-7800 or call your local chapter (listed in the
telephone directory)
World Wide Web address: http://www.arthritis.org
The Hip Society
c/o Richard B. Welch, M.D.
One Shrader Street, Suite 650
San Francisco, CA 94117
415/221-0665
Fax: 415/221-4023
The Society maintains a list of physicians who are specialists in
problems of the hip and provides physician referrals by geographic
area.
Acknowledgments
The NIAMS gratefully acknowledges the assistance of Thomas D.
Brown, Ph.D., of the University of Iowa; James Panagis, M.D., M.P.H.,
of the National Institutes of Health; and Harry E. Rubash, M.D., of
the University of Pittsburgh Medical Center, in the preparation and
review of this fact sheet.
The National Arthritis and Musculoskeletal and Skin Diseases
Information Clearinghouse (NAMSIC) is a public service sponsored by
the NIAMS that provides health information and information sources.
The NIAMS, a part of the National Institutes of Health (NIH), leads
the Federal medical research effort in arthritis and musculoskeletal
and skin diseases. The NIAMS sponsors research and research training
throughout the United States as well as on the NIH campus in
Bethesda, MD, and disseminates health and research information.
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