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Updated: Aug 24 2023

Osteomyelitis - Adult

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  • Summary
    • Osteomyelitis is the infection of bone characterized by progressive inflammatory destruction and apposition of new bone.
    • Diagnosis requires careful assessment of radiographs, MRI and determining the organism via biopsy and cultures.
    • Treatment is often a combination of culture-directed antibiotics and surgical debridement of nonviable tissue.
  • Epidemiology
    • Incidence
      • the exact incidence is unknown
    • Location
      • spine and ribs in dialysis patients
      • medial or lateral clavicle in IV drug abusers
      • foot and decubitus ulcers in diabetics
    • 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
  • Etiology
    • Pathophysiology
      • mechanism of spread
        • hematogenous
          • originated or transported by blood
            • may be due to bacterial or viral systemic illness
          • most common etiology in children
          • vertebrae are the most common hematogenous site in adults
          • S. aureus is the most common organism
        • contiguous-spread
          • associated with previous surgery, trauma, wounds, or poor vascularity
          • can be bacterial (most common), mycobacterial, or fungal in nature
        • direct-inoculation
          • penetrating injuries
          • open fractures
          • surgical contamination
      • pathobiology
        • planktonic stage
          • bacteria attach to an inert substrate and undergo apoptosis to create a matrix for biofilm
        • biofilm formation
          • biofilm is characterized by bacteria entering a no-growth, or sessile, phase, which makes them even more resistant to antibiotics that depend on replication to carry out their effect
          • biofilm is then made of an extracellular polymeric substance or exopolysaccharide
          • antibiotics are less effective due to difficulty penetrating the biofilm and bacteria lowering their metabolic rate
    • Associated conditions
      • orthopaedic manifestations
        • septic arthritis
        • abscess
      • medical conditions
        • immunosuppression
        • dialysis
        • IV drug use
        • diabetes
        • poor nutrition
        • vascular disease
    • Organism (see table below)
      • organism varies by age of the patient
      • S. aureus is most common in adults
      • Osteomyelitis Organism Table
      • Newborns
      • (younger than 4 mo)
      • S. aureus, Enterobacter species, 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
      • Unusual Osteomyelitis Organism Table
      • Salmonella
      • Sickle cell anemia patients (S. aureus is still most common)
      • Pseudomonas
      • IV drug use with AC or SC joint infection or puncture wound through rubber soled shoes
      • Bartonella
      • HIV/AIDS patient following cat scratch or bite
      • Fungal osteomyelitis
      • Immunosuppressed, long-term IV medications, or parenteral nutrition
      • Tuberculosis
      • Manifestations include Potts disease
  • Classification
    • Timing classification
      • acute
        • within 2 weeks
      • subacute
        • within one to several months
      • chronic
        • after several months
    • Cierny-Mader classification
      • Cierny-Mader Classification of Osteomyelitis
      • (describes anatomic involvement, host, treatment, prognosis)
      • Anatomic Location
      • Medullary
      • Stage 2
      • Superficial
      • Stage 3
      • Localized
      • Stage 4
      • Diffuse
      • Host type
      • Type A
      • Normal
      • Type BL
      • Locally compromised
      • Type BS
      • Systemically compromised
      • Type C
      • Treatment is worse to the patient than infection
  • Presentation
    • History
      • duration
      • prior treatments
      • characterize host
        • immunocompromised
    • Symptoms
      • pain
      • fever
        • more common in acute osteomyelitis
    • Physical exam
      • vital signs
        • fever, tachycardia, and hypotension suggest sepsis
      • inspection
        • erythema, tenderness, and edema are commonly seen
        • draining sinus tract
          • more common in chronic osteomyelitis
          • if able to probe bone through sinus, chronic osteomyelitis is present
      • motion
        • limp and/or pain inhibition with weight-bearing or motion may be present
        • assess the joints above and below the area of concern
      • neurovascular
        • assessment of vascular insufficiency locally or systemically
  • Imaging
    • Radiographs
      • recommended views
        • orthogonal plain radiographs of the affected extremity
      • findings
        • acute
          • imaging findings lag behind by 2 weeks
          • bone loss must be 50% before evident on plain films
        • chronic
          • bone lucency, sclerotic rim, osteopenia, periosteal reaction, and lysis around hardware
          • sequestrum: devitalized bone that serves as a nidus for infection
          • involucrum: formation of new bone around an area of bony necrosis
          • Brodie's abscess
      • sensitivity and specificity is variable
    • CT
      • indications
        • assist in diagnosis and surgical planning by identifying necrotic bone
      • sensitivity and specificity may be affected by hardware artifact and scatter
    • MRI
      • indications
        • assists in the diagnosis and surgical planning
        • best test for diagnosing early osteomyelitis and localizing infection
      • views
        • T2 sequences will show bone and soft tissue edema
      • findings
        • penumbra sign
          • T1 - dark central abscess with bright internal wall and dark external sclerotic rim
      • sensitivity and specificity
        • if negative rules out osteomyelitis
        • if positive may overestimate the extent of osteomyelitis
    • Nuclear medicine
      • technetium bone scan
        • indications
          • when radiographs are normal and MRI is not an option
        • sensitivity and specificity
          • highly sensitive but not specific
          • if negative rules out osteomyelitis
      • gallium scan
        • indications
          • diabetic foot or if MRI is not an option
        • sensitivity and specificity
          • cellulitis may cause false positive
          • if negative rules out osteomyelitis
  • Studies
    • Laboratory analysis
      • leukocyte count (WBC)
        • only elevated in 1/3 of acute osteomyelitis
      • erythrocyte sedimentation rate (ESR)
        • usually elevated in both acute and chronic osteomyelitis (90%)
          • a decrease in ESR after treatment is a favorable prognostic indicator
      • C-reactive protein
        • most sensitive test with elevation in 97% of cases
          • decreases faster than ESR in successfully treated patients
      • blood cultures
        • often negative, but may be used to guide therapy for hematogenous osteomyelitis
    • Microbiology
      • sinus tract cultures
        • not reliable for guiding antibiotic therapy
      • culture of bone
        • gold-standard for guiding antibiotic therapy
    • Histology
      • acute osteomyelitis
        • live osteocytes with numerous acute inflammatory cells (neutrophils)
      • chronic osteomyelitis
        • no nuclei in osteocytes with fibrosis of marrow and chronic inflammatory cells (lymphocytes)
  • Differential
    • Key differential
      • benign tumor
        • biopsy all infection, cultures all tumors
      • malignant tumor
        • biopsy all infection, cultures all tumors
      • healing fracture
  • Treatment
    • Goals
      • success in the treatment is dependent on various factors
        • patient factors
          • immunocompetence of patient
          • nutritional status
        • injury factors
          • the severity of the 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
      • suppressive antibiotics
        • indications
          • when operative intervention is not feasible
      • hyperbaric oxygen therapy
        • indications
          • can be used as adjunct in refractory osteomyelitis
    • Operative treatment
      • irrigation and debridement followed by organism specific antibiotics
        • indications
          • acute osteomyelitis that fails to improve on IV antibiotics
          • subacute osteomyelitis
          • abscess formation
          • chronic osteomyelitis
            • draining sinus
      • amputation
        • indications
          • chronic infection with pervasive wound or bone damage that is unable to be salvaged
  • Techniques
    • Antibiotic therapy
      • technique
        • antibiotics should be tailored to a 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
          • high rates of recurrence if suppressive antibiotics are discontinued
    • Irrigation & debridement
      • soft tissue
        • all devitalized and necrotic tissue should be removed
        • extensive debridement is essential to eradicate the infection
      • bone work
        • sequestrum must be eliminated from the body, or infection is likely to recur
        • debride bone until punctate bleeding is seen - "paprika sign"
      • 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
            • improves 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
      • instrumentation
        • bony stability is required for successful eradication of infection
        • external fixation preferred to internal fixation
        • surgical fixation techniques
          • antibiotic-impregnated acrylic (PMMA) Intramedullary nail
            • peak antibiotic elution is 24 hours after placement
            • duration of antibiotics elution is generally up to 4 months
          • Ilizarov technique
          • intramedullary nail with or without external fixation
          • Masquelet technique
          • in situ reconstruction
        • mechanism is thought to be related to improved angiogenesis
      • outcomes
        • often requires staged approach with multiple debridements and delayed soft tissue coverage
        • when combined with postoperative antibiotics tailored to a specific organism, treatment is often successful
    • Amputation
      • technique
        • amputation at the level that will eradicate infected tissue to healing tissue with capacity to heal
  • Complications
    • Persistence or extension of infection
    • Amputation
    • Sepsis
    • Malignant transformation
      • incidence
        • 1% in chronic osteomyelitis
        • most commonly squamous cell carcinoma (Marjolin's ulcer)
      • risk factors
        • chronic draining sinus
      • treatment
        • wide surgical resection
  • Prognosis
    • Despite surgical debridement and long-term antibiotics, recurrence rate of chronic osteomyelitis in adults is 30%
    • Poor prognosis in patients with major nutritional or systemic disorders
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