The presence of leukocytosis is inconsistent. Blood cultures are important but are negative in many cases. Elevated acute phase reactants, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), are sensitive but nonspecific findings. Serial determinations of ESR and CRP are helpful in monitoring the course of the illness and response to treatment. Direct subperiosteal or metaphyseal needle aspiration definitively establishes the diagnosis. Identification of bacteria in aspirated material by Gram stain can establish the diagnosis within hours of clinical presentation.
Plain radiographs can demonstrate soft tissue swelling such as the loss of the periosteal fat line within the first 3 days of symptoms, but bony lesions such as periosteal elevation and bone destruction are absent until after 10 to 14 days of symptoms (Fig. 117-2). Brodie abscess is a subacute intraosseous abscess that does not drain into the subperiosteal space and is classically located in the distal tibia. Sequestra, portions of
Figure 117-2 Multifocal acute osteomyelitis in a 3-week-old infant with multiple joint swelling and generalized malaise. Frontal (A) and lateral (B) radiographs of the left knee show focal destruction of the distal femoral metaphysis with periosteal reaction and generalized soft tissue swelling. Frontal (C) and lateral (D) views of the right knee show an area of focal bone destruction at the distal femoral metaphysis with periosteal reaction and medial soft tissue swelling. Needle aspiration of multiple sites revealed Staphylococcus aureus. (From Moffett KS, Aronoff SC: Osteomyelitis. In Jenson HB, Baltimore RS, editors: Pediatric Infectious Diseases: Principles and Practice, ed 2, Philadelphia, 2002, Saunders, p 1038.) avascular bone that have separated from adjacent bone, frequently are covered with a thickened sheath, or involucrum, both of which are hallmarks of chronic osteomyelitis.
Radionuclide scanning for osteomyelitis has largely been supplanted by magnetic resonance imaging, which is sensitive to the inflammatory marrow changes even during the earliest stages of osteomyelitis. Technetium-99m bone scans are useful for identifying multifocal disease. Gallium-67 scans are often positive if the technetium-99m bone scan is negative.
Osteomyelitis must be differentiated from infectious arthritis (see Chapter 118), cellulitis, pyomyositis, fasciitis, diskitis, trauma, juvenile idiopathic arthritis, bone cysts, histiocytosis, and malignancy.
Available @ StudentConsult.com
Initial antibiotic therapy for osteomyelitis is based on the likely organism for the age of the child, Gram stain of bone aspirate, and associated diseases (Table 117-1). Initial therapy includes an antibiotic that targets S. aureus and Kingella, such as oxacillin or nafcillin. Clindamycin or vancomycin should be used if methicillin-resistant S. aureus is suspected based on patient factors or local S. aureus epidemiology. For patients with sickle cell disease, initial therapy should include an antibiotic with activity against Salmonella.
Kingella kingae Penicillin G, oxacillin, or cefotaxime *Optimal specific therapy is based on susceptibilities of the organism that is isolated.