Harvey's Garden

Septic arthritis

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2 min read

Epidemiology

Etiology

  • Staphylococcus aureus
    • Most common in adults and children > 2 years
    • Frequently found in patients with arthritis following invasive joint procedures
  • Streptococci
  • N. gonorrheae
    • Most common in sexually active young adults
  • Gram-negative rods esp. E. coli and P. aeruginosa

Pathophysiology

Clinical features

Subtypes and variants

Prosthetic joint infection

  • Etiology by Timeline: c
    • <3 mo (Early): S. aureus, Gram-negative bacilli (P. aeruginosa).
      • Intraop contamination with high-virulence organisms
    • 3–12 mo (Delayed): S. epidermidis (coag-negative Staph), C. acnes.
      • Intraop contamination with low-virulence organisms
    • >12 mo (Late): Hematogenous seeding (S. aureus, Streptococcus spp.).
  • Diagnosis:
    • Screening: Serum ESR & CRP (high sensitivity; normal rules out PJI).
    • Best Initial Test: Arthrocentesis (Synovial WBC >3,000-10,000/μL, >80% PMNs).
    • Gold Standard: Intraop tissue culture (3–5 identical positive specimens).
    • Imaging: X-ray showing radiolucency around hardware, periosteal reaction, or loosening.
  • Management:
    • Empiric Abx: IV Vancomycin + Cefepime / Zosyn.
    • Early / Acute (<3 wks symptoms): DAIR (Debridement, Abx, Implant Retention) + oral Rifampin (penetrates Staph biofilm).
    • Delayed / Chronic: 2-stage revision (Hardware removal + Abx cement spacer -> 6 wks IV Abx -> Re-implantation).

Diagnostics

Treatment

  • Emergent Management
    • This is an orthopedic emergency requiring immediate action to prevent joint destruction.
    • Two priorities: Joint Drainage & IV Antibiotics.
    • ALWAYS aspirate the joint (arthrocentesis) before giving antibiotics.
  • Empiric IV Antibiotics (Start immediately after aspiration)
    • General/Gram (+) cocci: Vancomycin (to cover MRSA, the most common cause).
    • Sexually Active Young Adult: Ceftriaxone (for N. gonorrhoeae). Also treat for Chlamydia.
    • Gram (-) Rods / Immunocompromised: Vancomycin + Anti-pseudomonal (e.g., Cefepime, Ceftazidime).
    • Gram Stain Negative: Vancomycin + Ceftriaxone.
  • Joint Drainage
    • Serial Needle Aspiration: May be sufficient for easily accessible joints (e.g., knee).
    • Surgical Washout (Arthroscopy or Arthrotomy): Required for hip joint, failure of needle aspiration, or thick purulence.
  • Duration of Therapy
    • Nongonococcal: ~3-4 weeks total. Start with IV and can switch to oral agents when improving.
    • Gonococcal: Shorter course of ~7-14 days.

Graph View

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