“ Underlying pathogen varies with age (e.g. S. aureus, Streptococcus pneumoniae and Haemophilus influenzae in the elderly) and other dis...
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• Acute: soft tissue swelling, focal bone lucency and periostitis (periostium lifts in paediatric patients).
• The location of disease in the bone depends on patient age (i.e. area with richest blood supply):
- multifocal in neonates;
- epiphysis in infants/adults;
- metaphysis in children from ages 1 to 16 years.
– Sequestrum: A focus of necrotic bone that is separated from living bone by granulation tissue.
– Involucrum: A layer of living bone that forms around the necrotic bone focus.
– Cloaca: An opening into the involucrum through which exudate may escape.
– Sinus tracts may be seen leading to the skin surface.
• Cortical thickening and focal cortical lysis may also occur with chronic infection.
• Most sensitive and most useful for surgical planning.
• First sign is loss of normal marrow signal on T1 and T2/STIR hyperintensity.
• Sequestrum is low signal on T1/STIR, surrounding granulation tissue enhances with contrast.
• Look for tram track enhancement of a sinus tract and rim enhancement with an abscess.
• Three- and four-phase bone scans are used to assess infection (overall sensitivity 88%, specificity 36%)
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