This is a serious bone infection that occurs most often among children between the ages of five and nine, although it can develop in infants and adolescents. Without immediate and thorough treatment, the infection may damage the joints and the ends of the leg and arm bones, causing growth impairment and/or permanent disability. When the joint is infected by bacteria, the condition is called pyogenic arthritis.
WHEN SHOULD I SUSPECT THAT MY CHILD HAS OSTEOMYELITIS?
The first signs of osteomyelitis are complaints of pain with associated tenderness and an unwillingness to move the affected extremity. In many cases, the child develops a limp. In a baby, the first sign may be complete lack of movement in the affected limb. Fever, vomiting, swollen lymph glands and other signs of illness also may appear. There may be local swelling and redness and, if the joint is involved, a swollen knee, elbow, wrist or ankle.
HOW DOES OSTEOMYELITIS DEVELOP?
Osteomyelitis usually develops when bacteria, sometimes from another infection, such as a boil or an tooth, travel through the bloodstream to the bones. The infection usually settles in the matrix of a leg or arm bone, although it may develop in the feet, hands, pelvis, ribs or vertebrae. In babies under a year old, osteomyelitis tends to occur in several sites at a time, whereas in older children, only one bone usually is affected.
Although the original source of the infection is often impossible to identify, children with certain conditions have an increased risk of developing osteomyelitis. These conditions include infected burns, cat or dog bites, impetigo (a skin infection) and chicken pox lesions that have been scratched open and become infected. Some children with underlying conditions, such as sickle-cell disease or immune deficiencies, are more susceptible.
Osteomyelitis begins as a bacterial infection in the bone, which can progress to an abscess. Depending on the blood supply, the abscess may remain in the central portion of the bone or spread to the growing end of the bone and invade the joint, causing arthritis. This complication is more likely to occur in the first year of life because the communicating networks of blood vessels nourish both the growth centers and the ends of the bones. In older children, these networks are separated, so arthritis occurs less frequently, or may occur independent of osteomyelitis. As delicate cartilage is destroyed by the infection, dislocations and fractures can occur, leading to deformity and altered growth. Strangely enough, and for reasons that are not well understood, osteomyelitis sometimes stimulates faster bone growth.
IS MEDICAL ATTENTION NECESSARY?
Yes. A doctor should examine any child who has unexplained arm or leg pain, accompanied by fever, particularly if the limb is swollen and difficult to move.
HOW CAN THE DOCTOR TELL IF MY CHILD HAS OSTEOMYELITIS?
To reach a diagnosis, the doctor will examine the limb and take a blood sample to see if white blood cells are elevated (indicating infection) and to determine whether bacteria from the blood can be cultured in the laboratory. An important test is needle aspiration (withdrawal) of fluid from the affected bone or joint. By examining the fluid, the doctor can often determine the specific bacterium responsible and choose the best antibiotic with which to initiate treatment. To keep the pain of this test to a minimum, the child may be given an analgesic and local anesthetic at the site of the aspiration. An MRI may also be indicated.
Other possible tests include an X ray (which may not show bone changes until the infection has been present over a week) and a bone scan, in which a contrast material is injected to highlight bone destruction and may show the infection location much earlier than a conventional X ray.
HOW IS OSTEOMYELITIS TREATED?
If a child has signs and symptoms of osteomyelitis, intravenous antibiotic treatment starts immediately while the doctor awaits definitive test results. High dosages are administered for four to six weeks, until symptoms diminish and X rays demonstrate healing. A hospital stay is usually necessary, although the length will depend on the child's age and overall condition.
If antibiotics fail to bring improvement, or if pus is removed from a bone or joint during needle aspiration, the abscess may need to be drained surgically.
PREVENTING OSTEOMYELITIS
Fortunately, osteomyelitis is unusual in industrialized countries where children's health status is generally good. You can protect your child even more by getting prompt treatment for impetigo, boils, ear infections and other potential sources of bacteria, especially staph organisms that can enter the bloodstream and travel to the bone or joint. If your child is taking antibiotics for any kind of infection, make sure to complete the entire course, even if symptoms have gone away.
Hemophilus influenzae type B bacteria are responsible for some cases of pyogenic arthritis in infants and toddlers. Immunization against this type of bacteria is available and recommended by the American Academy of Pediatrics starting at two months of age. If you're not sure whether your child has been immunized, ask your pediatrician.
GETTING HELP
Call your doctor if your child:
• Has an unexplained limp
• Complains of localized pain, particularly in an arm or leg
• Has a swollen, tender arm or leg
• Has difficulty moving a joint
• Develops any of the above symptoms shortly after an illness that was accompanied by fever
• Has recently had a burn, animal bite, skin infection or other injury and develops any of the above symptoms
