What is osteomyelitis?
Osteomyelitis is a bacterial, or fungal, infection of the bone. Osteomyelitis affects about 2 out of every 10,000 people. If left untreated, the infection can become chronic and cause a loss of blood supply to the affected bone. When this happens, it can lead to the eventual death of the bone tissue.
Who is affected by osteomyelitis?
Osteomyelitis can affect both adults and children. The bacteria or fungus that can cause osteomyelitis, however, differs among age groups. In adults, osteomyelitis often affects the vertebrae and the pelvis. In children, osteomyelitis usually affects the adjacent ends of long bones. Long bones (bones in the arms or legs) are large, dense bones that provide strength, structure and mobility. They include the femur and tibia in the legs and the humerus and radius in the arms.
Osteomyelitis is not more common in a particular race or gender. However, some people are more at risk for developing the disease, including:
Symptoms and Causes
What causes osteomyelitis?
It can be caused by a variety of microbial agents (most common in staphylococcus aureus) and situations, including:
- An open injury to the bone, such as an open fracture with the bone ends coming out through the skin.
- A minor trauma, which can lead to a blood clot around the bone and then a secondary infection from seeding of bacteria.
- Bacteria in the bloodstream (bacteremia), which is deposited in a focal (localized) area of the bone. This bacterial site in the bone then grows, resulting in destruction of the bone. However, new bone often forms around the site.
- A chronic open wound or soft tissue infection can eventually extend down to the bone surface, leading to a direct bone infection.
What are the symptoms of osteomyelitis?
The symptoms of osteomyelitis can include:
- Pain and/or tenderness in the infected area.
- Swelling, redness and warmth in the infected area.
- Nausea, secondarily from being ill with infection.
- General discomfort, uneasiness, or ill feeling.
- Drainage of pus (thick yellow fluid) through the skin.
Additional symptoms that may be associated with this disease include:
- Excessive sweating.
- Lower back pain (if the spine is involved).
- Swelling of the ankles, feet, and legs.
- Loss or decrease of motion of a joint.
- Changes in gait (walking pattern that is a painful, yielding a limp) or unwillingness to bear weight in children.
Diagnosis and Tests
How is osteomyelitis diagnosed?
To diagnose osteomyelitis, the doctor will first perform a history, review of systems, and a complete physical examination. In doing so, the physician will look for signs or symptoms of soft tissue and bone tenderness and possibly swelling and redness. The doctor will also ask you to describe your symptoms and will evaluate your personal and family medical history. The doctor can then order any of the following tests to assist in confirming the diagnosis:
- Radiographs (X-Rays): These tests can show abnormalities of the bone. The abnormalities can include a focal decrease in density, which can suggest bone destruction from bacteria. It can also demonstrate an area where infected bone can be trapped by a bacterial infection.
- Magnetic Resonance Imaging (MRI): This imaging examination can show any fluid in the bone with greater sensitivity and precision. It is a helpful tool to see how far the infection has spread, if present.
- Blood tests: When testing the blood, measurements are taken to confirm an infection: a CBC (complete blood count), which will show if there is an increased white blood cell count; an ESR (erythrocyte sedimentation rate); and/or CRP (C-reactive protein) in the bloodstream, which detects and measures inflammation in the body.
- Blood culture: A blood culture is a test used to detect bacteria that has escaped into the bloodstream. A sample of blood is taken and then placed into an environment that will support the growth of bacteria. By allowing the bacteria to grow, the infectious agent can then be identified and tested against different antibiotics in hopes of finding the most effective treatment.
- Needle aspiration: During this test, a needle is used to remove a sample of fluid and cells from the vertebral space, or bony area. It is then sent to the lab to be evaluated by allowing the infectious agent to grow on media.
- Biopsy: A biopsy (tissue sample) of the infected bone may be taken and tested for signs of an invading organism.
- Bone scan: During this test, a small amount of Technetium-99 pyrophosphate, a radioactive material, is injected intravenously into the body. If the bone tissue is healthy, the material will spread in a uniform fashion. However, a tumor or infection in the bone will absorb the material and show an increased concentration of the radioactive material, which can be seen with a special camera that produces the images on a computer screen. The scan can help your doctor detect these abnormalities in their early stages, when X-ray findings may only show normal findings.
Management and Treatment
How is osteomyelitis treated?
The objective of treating osteomyelitis is to eliminate the infection and prevent the development of chronic infection. Chronic osteomyelitis can lead to permanent deformity, possible fracture, and chronic problems, so it is important to treat the disease as soon as possible.
Drainage: If there is an open wound or abscess, it may be drained through a procedure called needle aspiration. In this procedure, a needle is inserted into the infected area and the fluid is withdrawn. For culturing to identify the bacteria, deep aspiration is preferred over often-unreliable surface swabs. Most pockets of infected fluid collections (pus pocket or abscess) are drained by open surgical procedures. The reason for this is that antibiotics are ineffective at reaching pockets of infected fluid as they have no blood supply.
Antibiotic medications: Prescribing antibiotics is the first step in treating osteomyelitis. Antibiotics help the body get rid of bacteria in the bloodstream that may otherwise re-infect the bone. The dosage and type of antibiotic prescribed depends on the type of bacteria present and the extent of infection. While antibiotics are often given intravenously, some are also very effective when given in an oral dosage. It is important to first identify the offending organism through blood cultures, aspiration, and biopsy so that the organism is not masked by an initial inappropriate dose of antibiotics. The preference is to first make attempts to do procedures (aspiration or bone biopsy) to identify the organisms prior to starting antibiotics.
Surgery: Most well-established bone infections are managed through open surgical procedures during which the destroyed bone is scraped out. In the case of spinal abscesses, surgery is not performed unless there is compression of the spinal cord or nerve roots. Instead, patients with spinal osteomyelitis are given intravenous antibiotics. After surgery, antibiotics against the specific bacteria involved in the infection are then intensively administered during the hospital stay and for many weeks afterward.
Outlook / Prognosis
What is the outlook for patients with osteomyelitis?
With proper treatment, the outcome is usually good for osteomyelitis, although results tend to be worse for chronic osteomyelitis, even with surgery. Some cases of chronic osteomyelitis can be so resistant to treatment that amputation may be required; however, this is rare. Over many years, chronic infectious draining sites can evolve into a squamous-cell type of skin cancer; this, too, is rare. Any change in the nature of the chronic drainage, or change of the nature of the chronic drainage site, should be evaluated by a physician experienced in treating chronic bone infections. Because it is important that osteomyelitis receives prompt medical attention, people who are at a higher risk of developing osteomyelitis should call their doctors as soon as possible if any symptoms arise.
Where can I learn more about osteomyelitis?
For more information on osteomyelitis, contact the following organizations:
- NIH/National Arthritis and Musculoskeletal and Skin Diseases Information Clearinghouse
One AMS Circle Bethesda MD 20892-3675
- Back Pain Association of America, Inc.
P.O. Box 135 Pasadena MD 21123-0135