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Introduction
  • Infection of bone characterized by progressive inflammatory destruction and apposition of new bone
  • Epidemiology
    • risk factors
      • recent trauma or surgery
      • immunocompromised patients
      • illicit IV drug use
      • poor vascular supply
      • systemic conditions such as diabetes and sickle cell
      • peripheral neuropathy
  • Pathophysiology
    • mechanism of spread
      • hematogenous
        • originated or transported by blood
        • etiology of 20% of osteomyelitis
        • vertebrae most common site
        • S. aureus is most common organism
      • contiguous-focus
        • associated with previous surgery, trauma, wounds, or poor vascularity
        • can be bacterial (most common), mycobacterial, or fungal in nature
      • direct-inoculation
        • penetrating injuries
        • surgical contamination
    • biofilm formation
      • bacteria produce biofilm that covers necrotic bone and hardware
      • made of an extracellular polymeric substance or exopolysaccharide
      • antibiotics have difficulty penetrating biofilm
    • organism
      • organism varies by age of patient
      • S. aureus is most common in adults
Osteomyelitis Organism Table
Age group Most common organisms
Newborns
(younger than 4 mo)
S. aureus, Enterobacter species, and group A and B Streptococcus species
Children
(aged 4 mo to 4 y)
S. aureus, group A Streptococcus species, Kingella kingae, and Enterobacter species
Children, adolescents
(aged 4 y to adult)
S. aureus (80%), group A Streptococcus species, H. influenzae, and Enterobacter species
Adult S. aureus and occasionally Enterobacter or Streptococcus species
Sickle Cell Anemia Patients S. aureus is typically most common, but Salmonella species is pathognomonic
  • Prognosis
    • philosophy of treatment
      • infection elimination
      • bone union
    • despite surgical debridement and long-term antibiotics, recurrence rate of chronic osteomyelitis in adults is 30%
Classification
  • Timing classification
    • acute
      • within 2 weeks
    • subacute
      • within one to several months
    • chronic
      • after several months
  • Cierny classification
Cierny Classification of Osteomyelitis 
(describes anatomic involvement, host, treatment, prognosis)
 Anatomic Location
Stage I Medullary
Stage 2 Superficial
Stage 3 Localized
Stage 4 Diffuse
Host Type
Type A Normal  
Type B Compromised  
Type C Treatment is worse to patient than infection  
 
Presentation
  • Symptoms
    • pain
    • fever
      • more common in acute osteomyelitis
  • Physical exam
    • erythema, tenderness, and edema are commonly seen
    • limp and/or pain inhibition with weight-bearing or motion may be present
    • draining sinus tract  
      • more common in chronic osteomyelitis
Imaging
  • Radiographs
    • recommended views
      • orthogonal plain radiographs of the affected extremity
    • findings
      • often shows a lytic region surrounded by an area of sclerosis
      • may mimic a neoplastic processes
      • bone loss must be 30-40% before evident on plain films
      • sequestrum: devitalized bone that serves as a nidus for infection
      • involucrum: formation of new bone around an area of bony necrosis
  • CT
    • useful for surgical planning and determining extent of bony destruction
  • MRI
    • useful for soft tissue evaluation
  • Bone Scan
    • sensitivity comparable to MRI, but specificity is poor
Studies
  • Laboratory analysis
    • leukocyte count (WBC)
      • often elevated in acute osteomyelitis
      • may be normal in chronic osteomyelitis
    • erythrocyte sedimentation rate (ESR)
      • usually elevated in both acute and chronic osteomyelitis
      • decrease in ESR after treatment is a favorable prognostic indicator
    • C-reactive protein
      • decreases faster than ESR in successfully treated patients
  • Microbiology
    • blood cultures
      • may be used to guide therapy for hematogenous osteomyelitis
    • sinus tract cultures
      • not reliable for guiding antibiotic therapy
    • bone biopsy
      • gold-standard for guiding antibiotic therapy
Treatment
  • Goals
    • success in the treatment is dependent on various factors 
      • patient factors
        • immunocompetence of patient
        • nutritional status
      • injury factors
        • severity of injury as demonstrated by segmental bone loss
      • infection location
        • metaphyseal infections heal better than mid-diaphyseal infections
      • other factors affecting prognosis and treatment include:
        • residual foreign materials and/or ischemic and necrotic tissues
        • inappropriate antibiotic coverage
        • lack of patient cooperation or desire
  • Nonoperative Treatment
    • IV or oral antibiotic therapy for 4-6 weeks
      • indications
        • initial therapy in almost all situations
      • outcomes
        • rate of recurrence can be as high as 30%
    • hyperbaric oxygen therapy 
      • indications
        • can be used as adjunct in refractory osteomyelitis
  • Operative treatment
    • irrigation and debridement followed by organism specific antibiotics
      • indications
        • stage III and IV osteomyelitis
        • abscess formation
        • draining sinus
      • surgical fixation techniques 
        • Ilizarov technique
        • intramedullary nail with or without external fixation
        • Masquelet technique
        • free tissue transfer
        • in situ reconstruction
      • outcomes
        • when combined with postoperative antibiotics tailored to specific organism, treatment is often successful
Surgical Techniques
  • Antibiotic therapy
    • technique
      • antibiotics should be tailored to specific organism, preferably after a bone biopsy is obtained
      • chronic suppressive antibiotics may be useful in patients who are immunocompromised or in whom surgery is not feasible
  • Irrigation & Debridement
    • technique
      • debridement
        • all devitalized and necrotic tissue should be removed
        • extensive debridement is essential to eradicate infection
        • sequestrum must be eliminated from the body, or infection is likely to recur
      • hardware removal
        • any non-essential hardware should be removed
      • dead space management
        • goal is to replace dead bone and scar tissue with vascularized tissue
        • options include
          • vascularized bone grafts
          • local tissue flaps or free flaps
          • antibiotic-impregnated acrylic beads (PMMA)
          • vacuum-assisted closure
            • improve wound healing and dead space closure in multiple ways 
              • remove interstitial fluids
              • eliminate superficial purulence or slime
              • allow arterioles to dilate, which allows granulation tissue to proliferate
              • decrease in capillary afterload to promote inflow of blood
              • mechanical force on wound edges draws them in
      • stabilization
        • bony stability is required for successful eradication of infection
        • external fixation preferred to internal fixation
        • mechanism is thought to be related to improved angiogenesis
Complications
  • Persistence or extension of infection
  • Amputation
  • Sepsis
  • Malignant transformation (Marjolin's ulcer) 
    • most commonly squamous cell carcinoma

 

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