Osteomyelitis

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- An infection of the bone and bone marrow.

Causes and Incidence Osteomyelitis is caused by a pathogen that is introduced directly through an open fracture, penetrating trauma, or surgical procedure, or indirectly from another infection that spreads through the bloodstream or from adjacent tissues. The most common pathogens are Staphylococcus aureus, Streptococcus pneumoniae, Escherichia coli, Pseudomonas aeruginosa, and Haemophilus influenzae. The incidence is highest in childhood and early adolescence, and the disorder occurs more often in boys. Those undergoing hemodialysis, drug abusers, diabetics, and individuals with peripheral arterial insufficiency are also at risk.

Disease Process The long bones are most often involved. The invading pathogen travels to the metaphysis, located between the shaft and the epiphysis. The pathogen grows and multiplies in the metaphysis, producing pus, which eventually interferes with the blood supply in the bone, causing necrosis. An inflammatory response is set up, and macrophages are produced to combat the pathogens; necrosis continues, and the enlarging mass spreads through the bone cortex to contiguous tissues. New bone trabeculae are formed in an effort to keep the infection localized. The infection can spread to the bone marrow and to the skin through sinus tracts. Periodic drainage occurs until all dead bone is destroyed or excised. In adults the spine is oftenaffected.

Symptoms Pain, tenderness, edema, and warmth at the site are the most common manifestations. Bone pain on use or on palpation may be evident, as well as systemic symptoms such as fever, chills, sweats, malaise, weakness, headache, and nausea. Later signs include drainage from sinus tracts to the skin and fractures.

Potential Complications Osteomyelitis can lead to chronic infection, joint and skeletal deformities, and (in children) disturbed bone growth and limb shortening.

Diagnostic Tests The diagnosis is made from the clinical presentation; a history of antecedent infection or open trauma in the preceding 2 to 4 weeks; an elevated WBC count and erythrocyte sedimentation rate; and a positive radionucleotide scan with technetium phosphate. X-ray examination may reveal bone destruction, but only after 3 weeks or longer. Cultures of any identified mass are positive for the pathogen. If spread is via the bloodstream, serum cultures should be positive for the pathogen.

Treatments

Surgery
Surgical excision (saucerization) of infected and dead bone, sterilization of the abscess, bone grafts to affected site; amputation in some cases related to underlying diabetes.

Drugs
Antiinfective drugs specific for pathogen.

General
Splints to reduce joint pain; external fixation or casting for weakened bones to prevent fractures; initially bed rest, followed by progressive ambulation; dressing changes for draining wounds; hyperbaric oxygen therapy to increase circulating WBCs.

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