Last updated: November 4, 2014

ICD-9 Codes: Acute osteomyelitis, 730.0; chronic osteomyelitis, 730.1.
ICD-10 Codes: M86

Definition: Osteomyelitis is infection of bone and bone marrow.

Etiology: Most cases occur by either hematogenous or contiguous spread from local soft tissue infections or by direct inoculation (e.g., trauma). The highly vascular metaphysis (in children) or diaphysis (in adults) is a frequent site of hematogenous spread. Contiguous spread is more likely to occur in areas of vascular compromise. Acute hematogenous osteomyelitis is commonly caused by S. aureus, Streptococcus spp, and H. influenzae. Cases caused by contiguous spread may involve mixed aerobic and anaerobic organisms. Infections caused by prosthetic devices may be caused by coagulase-negative staphylococci, S. aureus, or gram-negative bacteria.

Pathology: In acute osteomyelitis, involved bony tissues show suppurative infiltrates, vascular congestion, edema, and thrombosis. Chronic osteomyelitis involvement shows devitalized bony tissues or fibrotic replacement.

Demographics: In infants and children, almost all cases are from hematogenous spread. Adults may develop infection from hematogenous dissemination or local spread. Local extension is more likely to involve bone in individuals with significant comorbidity such as diabetes or RA.

Risk Factors: Diabetes, RA, sickle cell disease, intravenous drug use, hemodialysis, trauma, recent fractures, prosthetic implants, and vascular insufficiency are risk factors.

Cardinal Findings: Acute signs of inflammation, such as erythema, swelling, and pain, may be localized over affected areas. However, many patients lack localizing signs and present instead with deep bony pain that may be referred some distance from the lesion. Contiguous spread to bone should be suspected around chronic soft tissue infections that may have draining sinuses. Fever is common but not universal. Single or multiple sites may be involved; children usually have multiple lesions. Tubular bones are commonly affected in children, and the vertebral column is frequently involved in adults.

Diagnostic Tests: Bone biopsy and culture are required for definitive diagnosis; cultures of sinus tracts do not reliably indicate the causative organism. Blood cultures can be useful but are positive in only a minority of cases. Leukocytosis and elevated ESR and CRP levels may be seen.

Imaging: Radiographs may show soft tissue swelling, periosteal elevation, cortical lucencies (with or without surrounding sclerosis), and destruction or erosion of the metaphysis, epiphysis, or diaphysis. Chronic osteomyelitis may be suggested by areas of osteolysis, periostitis, or sequestration. Scintigraphy and MRI may be used to define the extent of the osteomyelitis and are most useful in assessing chronic osteomyelitis.

Key to Diagnosis: Bone pain or radiographic abnormalities in patient with localized infection or possible bacteremia should suggest consideration of osteomyelitis. Osteomyelitis is more likely to occur in immunosuppressed hosts or those with comorbid risk factors.

Differential Diagnosis: Chronic soft tissue infections (cellulitis, abscesses) can be present without bone involvement. In such cases, radionuclide imaging studies (early) or plain radiographs (late) can be useful to suggest whether underlying bone is abnormal. Osteonecrosis and other causes of bony infarcts may be mistaken for osteomyelitis.

Therapy: If the organism is identified by bone biopsy/culture or blood culture, treatment with the appropriate antibiotic, administered parenterally, is required for 4 to 6 weeks.

Surgery: Surgical treatment may be required in chronic osteomyelitis for debridement of nonvital tissues or to drain abscesses. Hyperbaric oxygen therapy is a useful adjunct in cases of vascular insufficiency.

Prognosis: Outcome depends greatly on the time to diagnosis and the comorbidity. Children may recover completely; at the other end of the spectrum, adults with limb infections may require amputation.

McGuire JH. Osteomyelitis and infections of prosthetic joints. In: Isselbacher KJ, Braunwald E, Wilson JD, et al., eds. Harrison’s principles of internal medicine, 13th ed. New York: McGraw-Hill, 1994:558–560.

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