Pediatric Radiology > Musculoskeletal > Aggressive Lesions > Osteomyelitis


Osteomyelitis

Osteomyelitis is a bacterial infection of bone that primarily affects infants and young children. 1/2 of all cases occur before 5 years of age with 1/3 of these cases occurring before age 2. Patients may present clinically with pain, fever, and elevated WBC and/or ESR. Many patients will have a history positive for a recent respiratory tract infection or otitis media (most cases of osteomyelitis in the pediatric population have a hematogenous etiology).

Osteomyelitis usually occurs in the metaphyses or metaphyseal equivalents in children. Roughly 75% of all infections will involve the long bones (femur > tibia > humerus), while the remaining 25% will involve the flat bones, in particular the hip.

Radiographic findings of osteomyelitis:

  • plain films: deep soft-tissue swelling => displacement or obliteration of the the fat planes adjacent to the metaphysis (early finding); initial bony changes (i.e. loss of cortical white line with poorly-defined lucencies of the metaphysis) are not apparent until 7-10 days after the onset of symptoms; evidence of periosteal reaction becomes evident at about ten days; subacute and chronic changes include mixed bone lysis and sclerosis.
  • MRI (most specific): cortical destruction of the metaphysis with bone marrow edema (high signal on T2WI) as well as surrounding soft tissue edema.
  • bone scan: focal area of increased uptake in all three phases (angiographic/blood flow, soft tissue/blood pool, and skeletal phases); differs from cellulitis where there is increased activity in the blood flow and blood pool phases but a normal late phase.

* evidence of osteomyelitis is seen on MRI and bone scans early after the onset of symptoms.

Osteomyelitis involving the tibia of a 10-year-old male with foot pain, fever, and elevated ESR. A, AP radiograph of the right leg demonstrates focal demineralization with sclerosis of the distal tibia. B, Sagittal T2WI reveals marrow edema in the distal tibia which crosses the physis to invade the epiphysis. C, Bone scan reveals increased tracer uptake in the right tibia compared with normal uptake on the contralateral side.


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