What is the management for suspected prosthetic joint infection (PJI) in a patient with elevated CRP and ESR post Total Knee Replacement (TKR)?

Management of Suspected Prosthetic Joint Infection 35 Days Post-Bilateral TKR

This patient requires urgent diagnostic arthrocentesis followed by surgical intervention—the clinical presentation of swelling, redness, and warmth with markedly elevated inflammatory markers (CRP 39.6 mg/L, ESR >120 mm/h) at 35 days post-TKR is highly suspicious for prosthetic joint infection and mandates immediate action to prevent devastating morbidity. 1

Immediate Diagnostic Workup

Perform diagnostic arthrocentesis immediately unless surgery is already planned and antimicrobials can be safely withheld beforehand 1. The synovial fluid analysis must include:

• Total cell count and differential leukocyte count 1
• Aerobic and anaerobic cultures 1
• Consider crystal analysis if clinically indicated 1

Obtain plain radiographs of both knees to evaluate for prosthetic loosening, osteolysis, or other radiographic signs of infection 1

Draw blood cultures for aerobic and anaerobic organisms given the acute presentation and systemic inflammatory response 1

Critical Timing Consideration

If the patient is medically stable, withhold antimicrobial therapy for at least 2 weeks prior to obtaining cultures to maximize organism recovery 1. However, given this patient is 35 days post-op with acute symptoms, if they are systemically unwell or septic, empiric antibiotics should not be delayed for culture optimization 1

Interpretation of Inflammatory Markers

Your patient's inflammatory markers are concerning but require context:

• CRP of 39.6 mg/L is significantly elevated beyond what would be expected 35 days post-TKR 2
• ESR >120 mm/h is markedly abnormal at this timepoint 2
• Normal postoperative trajectory: CRP peaks around day 3 and normalizes by 1 month; ESR normalizes by 3 months 2

Important caveat: While these elevated markers strongly suggest infection, approximately 23-32% of culture-positive PJIs can present with normal CRP and ESR, particularly low-grade infections with coagulase-negative staphylococci or Propionibacterium acnes 3. Conversely, your patient's markedly elevated values make infection highly likely 1

Surgical Management Algorithm

The surgical approach depends on symptom duration and prosthesis characteristics 1:

Debridement and Implant Retention (DAIR) Criteria

DAIR may be considered ONLY if ALL of the following are met 1:

• Duration of symptoms <3 weeks OR joint age <30 days
• Well-fixed prosthesis on imaging
• Absence of sinus tract
• Organism susceptible to oral antimicrobial agents with biofilm activity

Your patient at 35 days post-op does NOT meet DAIR criteria based on timing alone 1

Prosthesis Removal Required

This patient requires prosthesis removal via either one-stage or two-stage exchange 1:

• Two-stage exchange is the gold standard in North America for established PJI 1, 4
• First stage: Remove prosthesis, debride thoroughly, place antibiotic-impregnated cement spacer 1
• Obtain 3-6 intraoperative tissue samples (or explanted prosthesis) for aerobic and anaerobic culture 1
• Consider sonication of removed implants to improve organism detection 5

Antimicrobial Therapy

Withhold empiric antimicrobials until adequate cultures are obtained if the patient is medically stable 1. Once cultures are obtained:

• Initiate pathogen-specific IV antimicrobial therapy based on culture results and susceptibilities 1
• Duration: 4-6 weeks of IV or highly bioavailable oral therapy following definitive surgical debridement 1
• For two-stage exchange: Continue antimicrobials between stages, though optimal duration remains debated 4

Common Pitfalls to Avoid

Do not rely solely on inflammatory markers for diagnosis—23% of culture-positive PJIs may have normal CRP/ESR, particularly chronic low-grade infections 3. Conversely, elevated markers are not 100% specific for infection 3, 6

Do not use advanced imaging (bone scans, MRI, CT, PET) routinely—these should not be part of standard PJI diagnosis 1

Do not start antibiotics before obtaining cultures unless the patient is septic or hemodynamically unstable 1

Do not attempt DAIR in this patient—at 35 days post-op with acute symptoms, the biofilm is mature and prosthesis removal is required 1

Multidisciplinary Collaboration

Immediate consultation with orthopedic surgery and infectious disease specialists is mandatory 1. This collaborative approach is essential to optimize both surgical and antimicrobial management and reduce morbidity and mortality 1