Classified by route of spread (hematogenous, contiguous spread, direct innoculation) or chronicity (acute or chronic), although any route of spread can lead to either acute or chronic disease. 

• Acute osteomyelitis: <2weeks duration

• Subacute osteomyelitis lasts <3 months but w/o acute sx

• Chronic osteomyelitis is characterized by bone necrosis.

The anatomic distributio nand clinical presentation is dependent on age of the patient, specific orgnaism and the presence of any underlying disorders, suc has vascular insufficiency or compromised immunity.

• Adults: osteo typically arises from their contiguous spread or direct innoculation, such as in diabetic foot infections, open fx, or as a complication of surgery. Infection is usually polymicrobial.

• Children: hematogenous spread of infection is more common; usually from staph aureus.

Definitions:

• Osteitis: inflammation/infection of the cortex

• Periostitis: inflammation/infection of the periosteum

• Sequestrum: piece of necrotic bone that is separated from viable bone by granulation tissue. A sequestrum is a surgical lesion that can chronically harbor living organisms and function as a nidus for recurrent infection if not resected.

• Involucrum: living bone surrounding necrotic bone.

• Cloaca: opening on the involucrum.

• Sinus tract: opening from the infection to the skin surface

• Brodie abscess is a form of subacute osteo characterized by central lucency and peripheral sclerosis. the radiographic ddx of a brodie abscess is an osteoid osteoma. 

RADIOGRAPHIC FINDINGS