Imaging abnormalities in osteomyelitis

Imaging modality	Abnormal findings
Plain radiograph*	Deep soft tissue swelling (3 days after onset)
	Periosteal reaction or elevation (10 to 21 days after onset)
	Lytic sclerosis (≥1 month after onset)
Magnetic resonance imaging	Bone marrow inflammation (decreased signal in T1-weighted images; increased signal in T2-weighted images)
	Edema in marrow and soft tissues
	Penumbra sign (high-intensity-signal transition zone between abscess and sclerotic bone marrow in T1-weighted images)
	With gadolinium enhancement: absent blood flow, suggestive of necrosis or abscess
Three-phase bone scan	Focal uptake of tracer in the third phase (delayed phase)
Computed tomography	Increased density of bone marrow
	Cortex destruction
	Periosteal reaction (new bone formation) formation
	Periosteal purulence
	Sequestra (devitalized, sclerotic bone)
Ultrasonography	Fluid collection adjacent to bone without intervening soft tissue
	Thickening of periosteum
	Periosteal elevation

* The timing and typical sequence of radiographic changes may vary with the site of infection and age of the patient.

References:

Browne LP, Mason EO, Kaplan SL, et al. Optimal imaging strategy for community-acquired Staphylococcus aureus musculoskeletal infections in children. Pediatr Radiol 2008; 38:841.
Jaramillo D, Treves ST, Kasser JR, et al. Osteomyelitis and septic arthritis in children: Appropriate use of imaging to guide treatment. AJR Am J Roentgenol 1995; 165:399.
Saigal G, Azouz EM, Abdenour G. Imaging of osteomyelitis with special reference to children. Semin Musculoskelet Radiol 2004; 8:255.
Schmit P, Glorion C. Osteomyelitis in infants and children. Eur Radiol 2004; 14 Suppl 4:L44.

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