What is the management of bacterial infections of joint prostheses?

Management of Bacterial Infections of Joint Prostheses

The optimal management of prosthetic joint infection (PJI) requires a combination of surgical intervention and pathogen-specific antimicrobial therapy tailored to the clinical presentation, with treatment decisions based on infection timing, prosthesis stability, and causative organisms. 1

Diagnosis of PJI

Clinical Presentation

• Suspect PJI in patients with:
  • Sinus tract or persistent wound drainage over a joint prosthesis
  • Acute onset of a painful prosthesis
  • Chronic painful prosthesis, particularly without pain-free interval after implantation
  • History of wound healing problems 1

Diagnostic Workup

1. Laboratory tests:

   • Sedimentation rate and CRP (combination provides best sensitivity/specificity) 1
   • Plain radiographs 1

2. Joint aspiration:

   • Perform diagnostic arthrocentesis in all suspected acute PJI cases
   • Include cell count, differential leukocyte count, and aerobic/anaerobic cultures
   • Withhold antibiotics for at least 2 weeks prior to aspiration when medically stable 1

3. Blood cultures:

   • Obtain if fever present, symptoms acute, or high risk of bacteremia 1

4. Intraoperative diagnosis:

   • Collect 3-6 periprosthetic tissue samples for culture
   • Consider histopathological examination of periprosthetic tissue
   • Explanted prosthesis can be submitted for sonication and culture 1

Definitive Diagnosis Criteria

PJI is definitively diagnosed when any of these are present:

• Sinus tract communicating with the prosthesis
• Purulence around the prosthesis without other etiology
• Two or more cultures yielding the same organism
• Acute inflammation on histopathologic examination 1

Treatment Approach

Surgical Management Options

1. Debridement with prosthesis retention:

   • Appropriate for:
     • Duration of symptoms <3 weeks OR joint age <30 days
     • Well-fixed prosthesis
     • Absence of sinus tract
     • Causative organism susceptible to oral antibiotics 1

2. Prosthesis removal:

   • One-stage exchange: Consider when:

     • Good soft tissue
     • Organism identified preoperatively
     • Good bone stock
     • Organism susceptible to oral antibiotics with high bioavailability 1

   • Two-stage exchange: Preferred for:

     • Poor soft tissue
     • Difficult-to-treat organisms
     • When bone grafting required 1

Antimicrobial Therapy

1. Empirical therapy (while awaiting culture results):

   • Vancomycin (15 mg/kg IV every 12 hours) plus
   • Cefepime (2 g IV every 12 hours) or meropenem (1 g IV every 8 hours) 2, 3
   • Tailor based on presentation type - early post-operative infections more likely polymicrobial (41%) compared to late acute infections (10%) 3

2. Pathogen-specific therapy:

   • Methicillin-susceptible staphylococci: Nafcillin 1.5-2g IV every 4-6h or cefazolin 1-2g IV every 8h
   • Methicillin-resistant staphylococci: Vancomycin 15 mg/kg IV every 12h
   • Pseudomonas: Cefepime 2g IV every 12h or meropenem 1g IV every 8h
   • Enterobacteriaceae: IV β-lactam based on susceptibility
   • Enterococci/Streptococci: Penicillin G 20-24 million units IV/24h
   • Propionibacterium acnes: Penicillin G 20 million units IV/24h 2

3. Biofilm considerations:

   • For staphylococcal infections, rifampin-based combinations show >77% success in early PJI with prosthesis retention 4
   • Fluoroquinolones preferred for gram-negative PJI 4
   • Biofilm formation on implant surfaces impairs antibiotic penetration 5

Treatment Duration

• Standard: 4-6 weeks of pathogen-specific antimicrobial therapy
• For staphylococcal infections with debridement and implant retention:
  • 3 months for hip prostheses
  • 6 months for knee prostheses 2

Special Considerations

Risk Factors for Treatment Failure

• Compromised immune status
• Bone loss
• Necrosis of soft tissues around the joint 6
• Polymicrobial infections
• Difficult-to-treat organisms 1

Common Pitfalls to Avoid

• Inadequate surgical debridement
• Insufficient number of culture specimens (aim for 3-6)
• Starting antibiotics before obtaining cultures
• Failure to recognize biofilm-associated infections
• Not considering prosthesis removal in chronic infections 1

Monitoring During Treatment

• Monitor for antibiotic side effects:
  • Vancomycin: nephrotoxicity (up to 32%)
  • Fluoroquinolones: QTc prolongation, tendinopathy
  • All antibiotics: risk of C. difficile colitis 2
• Regular clinical assessment for treatment response
• Follow inflammatory markers (ESR, CRP) 1

PJI management requires a multidisciplinary approach with infectious disease specialists and orthopedic surgeons working together to optimize outcomes and preserve joint function while eradicating infection 1, 7.