What is It?

Osteomyelitis is an infection of the bones that occurs either via hematogenous spread (most common in children), bacterial spread from local (contiguous) infections (cellulitis or septic arthritis), or traumatic inoculation. Long bones are more likely to be affected, with the femur being the most commonly affected bone (see below).

NEJM osteo

 

Skeletal Distribution of Acute Osteomyelitis in Children. From: Peltola H, Pääkkönen M. N Engl J Med 2014;370:352-360.

Epidemiology:

  1. Who is affected?
    • In developed countries, annual incidence is 8 out of 100,000 children. In developing countries, the incidence is much higher
    • Boys are affected twice as much as girls
  2. Who are the major pathogenic players?
    • Skin organisms predominate!
      • S. aureus is the most common etiologic agent
        • S. aureus possess virulence factors making it especially good at infecting bone
      • S. pyogenes 
    • Other common organisms
      • S. pneumoniae, H. influenza (though less common given vaccination; often affects joints, as compared to bones)
      • Kingella Kingae (most common in children under 4)
    • Sickle Cell disease
      • Consider Salmonella (though staph/strep still more common)
    • Neonatal Osteomyelitis
      • The organisms listed above still cause infections, but can also see: GBS, coag. negative Staph, Enterobacteriaceae

Clinical Presentation and Management

  1. Clinical Presentation 
    • Most common findings in children with osteomyelitis are pain of affected area and loss of function, however 2 distinct clinical syndromes have been described:
      • Children presenting with fever, localized pain, who appear acutely ill (likely septic)
      • A more indolent course, with gradual onset of pain and concurrent loss of function. In this presentation, the child may be afebrile or have low-grade fevers
    • As the lower extremity is more commonly affected, a common presentation is a child with a limp
    • Always consider osteomyelitis when dealing with a fever of unknown origin
    • Neonatal osteomyelitis is more likely to be associated with septic arthritis as well as be multi-focal
  2. Diagnosis
    • Physical Exam: As above, there are two main presentations, but most commonly children will demonstrate:
      • Fever
      • Localized erythema, swelling, inability to bear weight
    • Lab Studies
      • Serum Inflammatory Markers (CRP/ESR)
      • Blood Cultures (large studies show blood cultures positive in 48% [Peltola et al.])
      • CBC (may show mild-moderate leukocytosis, although normal white count does not exclude the diagnosis)
    •  Imaging
      • MRI is the most sensitive modality (Sensitivity: 88-100%, Specificity: 75-100%. [Song et al.])
      • Bone Scintigraphy
      • Plain Radiographs: Early in disease will show soft tissue swelling. (Sensitivity: 43-75%; Specificity: 75-83%)
    •  Microbiologic Data
      • Blood cultures as above
      • Bone biopsy, debridement
      • Abscess drainage, if applicable
  3. Treatment:
    • Choice of antibiotic: Empiric therapy in children should adequately cover S. aureus based on local susceptibility patterns (If suspecting osteomyelitis in a neonate, also need to consider Gram-negative organisms).
      • First Generation Cephalosporin (e.g. cefazolin)
      • Anti-staph Penicillin (nafcillin, oxacillin, etc)
      • Clindamycin (if suspecting MRSA and local resistance to clindamycin is low)
      • Vancomycin
      • Linezolid
    • Choice between IV and PO antibiotics
      • Historically, AHOM treated with long courses of IV antibiotics
      • Recent data suggests that a 2-4 day course of IV antibiotics, followed by oral antibiotics is as efficacious as IV therapy alone in uncomplicated cases (Peltola et al)
    • Duration of therapy
      • Historically, treatment duration ranged from 4-8 weeks
      • Recent data suggests that 3 week courses may be appropriate in carefully selected patients (Peltola et al, Song et al).
  4.  Conclusions
    • In pediatric patients, osteomyelitis is most often a hematogenous infection
    • S. aureus and S. pyogenes are the most common etiologic agents
      1. However, in small children, always consider Kingella spp.
    • Most common presenting complaints are fever and loss of function (lower extremities affected more commonly than upper extremities)
    • MRI is the most sensitive diagnostic modality
    • Initial Treatment is aimed at Staph and Strep, while consulting local susceptibility patterns
    • In uncomplicated cases following initial IV treatment, oral regimens have been shown to be as effective as IV regimens.
Case Presentation Radiographic Findings:
  • Altered marrow signal intensity of the distal left femur with low T1 and hyper intense T2 and PDFS signals. A focal destruction of the posteromedial distal femoral cortex is noted with elevated periosteum and periosteal reaction as well as subperiosteal 3.0 x 1.2 cm. cystic collection is noted with low T1 and hyper intense PDFS signal intensity.
  • Inflammatory changes with oedema signal and mild muscle enlargement are seen within the distal thigh and periarticular musculature with hypointense T1 and hyperintense T2 and PDFS signal.
  • Normal both hip joints with no evidence of significant joint effusion or septic arthritis.
  • The findings are those of distal femoral osteomyelitis with subperiosteal abscess and inflammatory myositis of the distal thigh muscles.

 

Faculty Reviewer: Michael Koster, MD

 

References

  1. Akakpo-Numado GK et al. “Current Bacterial Causes of Osteomyelitis in Children with Sickle Cell Disease” Sante 2008;18(2)67-70
  2. Conrad DA. “Acute Hematogenous Osteomyelitis.” Peds in Review 2010;31(11)
  3. Pääkkönen M, Peltola H. “Antibiotic treatment for acute hematogenous osteomyelitis of childhood: Moving towards shorter courses and oral administration.” International Journal of Antimicrobial Agents 2011;38:273-280
  4. Peltola H, Pääkkönen M, Kallio P, Kallio MJ. Short- versus long-term antimicrobial treatment for acute hematogenous osteomyelitis of childhood: prospective, randomized trial on 131 culture-positive cases. Pediatr Infect Dis J 2010;29:1123-1128
  5. Peltola H, Pääkkönen M. “Acute Osteomyelitis in Children.” N Engl J Med 2014;370:352-360.
  6. Song KM, Sloboda JF. “Acute Hematogenous Osteomyelitis in Children.” J Am Acad Orthop Surg 2001;9(3)166-75