Pediatric Acute Osteomyelitis (Greater Than 18 Months)

  • Etiology:
    — Trauma
    — Direct spread
    — Hematogenous spread from asymptomatic or symptomatic bacteremia
    — Infection starts in marrow space with significant edema with proliferation of excess white blood cells and bacterial growth and through bony canals the infected fluid permeates outward and elevates the periosteum
    — Most commonly due to Staphylococcus aureus or Salmonella in sickle cell disease
  • Imaging:
    — Most commonly occurs at metaphysis and metaphyseal equivalents (apophyses, areas at the junction of bone and cartilage in flat bones) both of which are highly vascular with slow blood flow
    — Physis is relative barrier for spread of infection from approximately 18 months of age until physeal closure
    — Infection can spread into joint space or subperiosteal space or soft tissues or diaphysis of bone
    — Most common regions involved are extremities and pelvis with ischiopubic synchondrosis a common site
    — See continuous periosteal reaction, deep soft tissue edema, lack of extra osseous soft tissue mass
  • Imaging US: Can identify bone destruction which appears as cortical irregularity or small cortical defects or occasional fluid collection
  • Imaging MRI:
    — T1WI post contrast: Help to identify drainable collections
  • DDX: Lucent bone lesions that extend to epiphysis are chondroblastoma, chondrosarcoma, giant cell tumor, osteomyelitis
  • Complications: Subperiosteal abscess which is a poor prognostic finding, intramedullary abscess
  • Treatment: Antibiotics
  • Clinical: Multicentric in 10% – think of infective endocarditis and Lemierre syndrome as source

Osteomyelitis Methicillin-resistant Staphylococcus Aureus (MRSA)

  • Etiology: Methicillin-resistant Staphylococcus aureus
  • Imaging Radiograph: Can be normal
  • Imaging MRI:
    — T1WI: Marrow has speckled or mottled or heterogenous appearance with small areas of hypointensity
    — T1WI post contrast: Enhancement pattern is coral reef pattern with lack of enhancement of marrow, subperiosteal abscesses seen
    — T2WI: Marrow has coral-like pattern of multiple small areas of hyperintensity
  • DDX:
  • Complications: Multiple tiny abscesses in marrow
  • Treatment: Antibiotics
  • Clinical: Progresses rapidly and must be treated emergently

Radiology Cases of Acute Osteomyelitis (Greater Than 18 Months)

Radiology Cases of Acute Osteomyelitis (Greater Than 18 Months) of the Hip

Radiograph and nuclear medicine bone scan of osteomyelitis of the femur
AP radiograph of the pelvis was unremarkable. Nuclear medicine bone scan shows increased radiotracer uptake in the left femoral head and neck and proximal femur.

Radiology Cases of Acute Osteomyelitis (Greater Than 18 Months) of the Rib

CT and MRI of osteomyelitis of the rib
Axial CT without contrast of the chest (above) shows bilateral axillary adenopathy and soft tissue swelling over the left lateral chest wall and associated rib destruction. Coronal T2 MRI of the chest (below left) shows a high signal intensity fluid collection between the skin and the ribs with surrounding edema. Axial T1 MRI with contrast of the chest (below right) shows extensive enhancement of the left ribs and surrounding muscle.

Radiology Cases of Acute Osteomyelitis (Greater Than 18 Months) of the Sacrum

MRI of osteomyelitis of the sacrum
Axial T2 MRI of the sacrum (above) shows large areas of bright signal in the left sacrum and in the left sacroiliac joint that show diffuse enhancement on axial T1 MRI with contrast (below).