Osteomyelitis

Question 1

Osteomyelitis

Definition

Answer 1

Severe and debilitating disease caused by infection of the bone

Question 2

Osteomyelitis

Pathogenesis

Answer 2

• Hematogenous spread
  
  • Common in underdeveloped countries
  • More likely in children < 20 y/o in developed countries
• Contiguous infection
  
  • From wounds such as foot ulcers in diabetics
  • More common adults in developed countries
• Direct inoculation
  
  • Trauma e.g. compound fractures
  • Surgery

Question 3

Osteomyelitis

Etiologies

Answer 3

• Typical pathogens
  
  • Staph aureus ⇒ most common (60%)
  • β-hemolytic Strep ⇒ 2nd most common
  • S. epidermidis
  • Coliforms (GNR) ⇒ E. Coli, Klebsiella, Pseudomonas etc.
  • Children < 20 y/o in developed countries ⇒ H. influenzae and β-hemolytic Strep most common
• Atypical pathogens:
  
  • Sickle cell anemia pts ⇒ Salmonella
  • IV drug user ⇒ Pseudomonas
  • AIDS pts ⇒ fungi and mycobacterium
    
    • MTb infection in the spine ⇒ Potts disease

Question 4

Osteomyelitis

Pathophysiology

Answer 4

• Organism travels to metaphysis where blood flow is slow
• Leaves the capillaries and enters the tissue
• Host can respond by walling it off ⇒ Brodie’s abscess
  
  • Becomes sterile vs site of chronic infection
• If infection expands and spreads ⇒ ± large area of bone necrosis called a sequestrum
  
  • Surrounding bone will become dense in an attempt to wall off the infection
• Isolation failure ⇒ further spread through cortex to subperiosteum
• From there it can gain access to:
  
  • Joint space
    
    • Uncommon except in children d/t vascular epiphyseal plate
  • Sinus tracts within the skin

Question 5

Osteomyelitis

Clinical Manifestations

Answer 5

Often an insidious presentation:

• Focal pain
• Overlying warmth, erythema, swelling
• Fever, sweats
• Drainage

Question 6

Osteomyelitis

Diagnosis

Answer 6

• Labs:
  
  • ↑ WBC
  • ↑ ESR / CRP
    
    • Sensitive but not specific
• Radiologic studies:
  
  • Plain films
    
    • Early ⇒ osteopenia or lytic lesions
    • Late ⇒ sclerotic changes
  • Nuclear medicine studies
    
    • Bone scan, WBC scan ⇒ both show ↑ uptake in infected bone
  • CT scan or MRI ⇒ can show enhancement, edema in bone
• Microbiology:
  
  • Blood cultures
    
    • Usu. ⊖ unless occurring w/ active endovascular infection such as endocarditis
  • Bone biopsy with culture and path
    
    • Gold standard for dx

Question 7

Osteomyelitis

Treatment

Answer 7

• Antibiotics
  
  • Need a long course for cure (6-12 weeks)
  • Usu. need IV
• ± Surgical debridement of necrotic bone
• Remove any hardware if possible