ACR Codes: 4.2
Osteomyelitis may result from open injury to bone and surrounding soft tissue, from hematogenous and local spread from adjacent tissues and as a postoperative complication(1). The specific organism isolated in bacterial osteomyelitis is often associated with the age of the patient or a common clinical scenario (i. e., trauma or recent surgery). Staphylococcus aureus is implicated in most patients with acute hematogenous osteomyelitis. Staphylococcus epidermidis, S. aureus, Pseudomonas aeruginosa, Serratia marcescens and Escherichia coli are commonly isolated in patients with chronic osteomyelitis.
Treatment generally involves clinical evaluation, imaging evaluation for disease extent, laboratory determination of microbial etiology and susceptibilities, antimicrobial therapy and, if necessary, debridement, dead-space management and stabilization of bone. Localized bone pain, erythema and drainage around the affected area may be present. The cardinal signs of subacute and chronic osteomyelitis include draining sinus tracts, deformity, instability and local signs of impaired vascularity, range of motion and neurologic status.
When there is clinical suspicion for osteomyelitis after physical examination and history, baseline radiographs should be performed followed by magnetic resonance imaging when available to define the extent of osteomyelitis and cellulitis. When MRI is not available, bone scans are useful for determining the extent of the infection. Laboratory tests may show leukocytosis (especially in the acute presentation) and elevations in the erythrocyte sedimentation rate and C-reactive protein level may be noted. Blood cultures are positive in as high as one-half of children with acute osteomyelitis.
In acute osteomyelitis, the radiographs may be negative or may show only soft tissue swelling and periosteal reaction. Evidence of medullary destruction may not appear until approximately two weeks after the onset of infection. Positive radiographic findings, when present include osteolysis, periosteal reaction and sequestra (segments of necrotic bone separated from living bone by granulation tissue).
A bone abscess found during the subacute or chronic stage of hematogenous osteomyelitis is known as a Brodie's abscess. Magnetic resonance imaging (MRI) is the most sensitive test for evaluating osteomyelitis and the areas of osteomyelitis and cellulitis show high signal intensity on T2-weighted MR images enhancement on postcontrast T1-weighted MR images.
Reference(s): 1. Resnick D, Niwayama G. Osteomyelitis, septic arthritis, soft tissue infection: Mechanisms and situations. In Resnick D, ed. Diagnosis of Bone and Joint Disorders. W. B. Saunders, Philadelphia, 1995, pp.2325-2418.
2. Waldvogel FA, Medoff G, Swartz MN. Osteomyelitis: a review of clinical features, therapeutic considerations and unusual aspects (first of three parts). N Engl J Med 1970;282:198-206.
3. Waldvogel FA, Medoff G, Swartz MN. Osteomyelitis: a review of clinical features, therapeutic considerations and unusual aspects (second of three parts). N Engl J Med 1970;282:260-6.
4. Waldvogel FA, Medoff G, Swartz MN. Osteomyelitis: a review of clinical features, therapeutic considerations and unusual aspects (third of three parts). N Engl J Med 1970;282:316-22.