Osteomyelitis in children

Background

Microbiology

• Staphylococcus aureus
• Streptococci
• Kingella kingae, especially for discitis

Pathophysiology

• Etiology is mostly due to hematogenous spread
• Bones have increased vascular supply until about 7 years of age

Investigations

• X-ray
  • For long bones, X-ray can show changes quickly
    • 3 days after onset of symptoms: soft tissue swelling at the metaphysis
    • 3-7 days: obliteration of the translucent fat planes by edema
    • 10-21 days: bone destruction, osteopenia, cortical thickening, periosteal reactions
  • For membranous or irregular bones, bony destruction and periosteal elevation are seen 2 to 3 weeks later than long bones
  • For pelvic and vertebral bones, x-ray is unlikely to be helpful
• MRI
  • Usually reserved for cases where x-ray is unlikely to be helpful, or where x-ray was negative but clinical suspicion remains

Management

• Start with intravenous therapy targetting Staphylococcus aureus, such as cefazolin
• Step down to oral therapy such as cephalexin once:
  • Afebrile for 48 hours
  • Decreased pain, swelling, and erythema
  • WBC normalized
  • C-reactive protein consistently decreasing
• Total duration is 4 weeks for typical hematogenous osteomyelitis