Residency · Residency · Orthopedic Surgery
Prosthetic Joint Infection: Diagnosis and Management
Introduction
Prosthetic joint infection (PJI) is one of the most challenging complications following total joint arthroplasty, occurring in approximately 1 to 2% of primary and 3 to 5% of revision arthroplasty procedures. PJI leads to significant patient morbidity, prolonged treatment courses, and enormous healthcare costs. A systematic approach to diagnosis and evidence-based management strategies are essential for the orthopedic surgeon.
Classification
By Timing of Onset
Early postoperative infections (within 3 months) are typically caused by virulent organisms inoculated at the time of surgery. Delayed or chronic infections (3 to 12 months) are often caused by less virulent organisms with an insidious onset. Late or hematogenous infections (beyond 12 months) are secondary to bacteremia from distant sources such as dental, urinary, or skin infections.
Common Organisms
Staphylococcus aureus (including MRSA) is the most common organism in acute PJI. Coagulase-negative staphylococci (S. epidermidis) are the most common in delayed and chronic infections. Streptococcal species are associated with hematogenous seeding. Gram-negative organisms (Enterobacteriaceae, Pseudomonas) are more common in immunocompromised hosts. Cutibacterium acnes is particularly relevant in shoulder arthroplasty. Culture-negative infections account for 5 to 15% of PJI cases.
Diagnosis
Clinical Presentation
Acute PJI presents with pain, warmth, erythema, wound drainage, and systemic signs of infection. Chronic PJI presents with persistent pain, stiffness, and progressive loosening on radiographs. Any persistently painful or stiff joint replacement should raise suspicion for infection.
Serologic Markers
ESR and CRP are the recommended initial screening tests, with combined sensitivity exceeding 95% when both are elevated. D-dimer has emerged as a useful adjunctive marker, particularly when CRP is equivocal.
Synovial Fluid Analysis
Joint aspiration is the cornerstone of PJI diagnosis. A synovial white blood cell count threshold of 3,000 cells per microliter is used for chronic PJI, with lower thresholds in the acute postoperative period. A neutrophil percentage greater than 80% is suggestive of infection. Synovial alpha-defensin is a highly sensitive and specific biomarker with a lateral flow assay available for intraoperative use. Leukocyte esterase is a rapid, inexpensive strip test with high specificity.
MSIS/ICM Criteria (2018 Modified)
Major criteria (one is diagnostic) include two positive cultures with the same organism or a sinus tract communicating with the joint. Minor criteria are part of a scored system incorporating elevated ESR/CRP, elevated synovial WBC, positive alpha-defensin, elevated synovial PMN percentage, and elevated CRP or D-dimer. A combined score of 6 or greater is considered infected, while 2 to 5 is inconclusive and warrants further workup.
Intraoperative Assessment
At least 3 to 5 tissue samples should be sent for culture (not swabs), and cultures should be held for 14 days to detect slow-growing organisms. Frozen section histology uses a threshold of 5 or more PMNs per high-power field in at least 5 fields. Sonication of explanted components improves culture sensitivity, particularly in patients already on antibiotics.
Management Strategies
| Strategy | Indications | Eradication Rate | Key Features |
|---|---|---|---|
| DAIR | Acute infection (< 3-4 weeks); well-fixed implant | 50-70% | Exchange modular components; IV antibiotics 6 weeks |
| Two-Stage Exchange | Chronic PJI (gold standard) | 85-95% | Explant + spacer → antibiotic holiday → reimplantation |
| One-Stage Exchange | Known organism; susceptible pathogen; adequate soft tissue | ~90% (selected patients) | Single surgery; shorter treatment; lower cost |
| Chronic Suppression | Non-surgical candidates | Does not eradicate | Long-term oral antibiotics; palliative |
| Resection Arthroplasty (Girdlestone) | Failed exchanges; non-reconstructable | Variable | Flail limb; salvage |
| Arthrodesis | Failed knee reimplantation | High | Stable but stiff limb |
| Amputation | Refractory infection; sepsis; limb-threatening | N/A | Last resort |
Debridement, Antibiotics, and Implant Retention (DAIR)
DAIR is indicated for acute infections (within 3 to 4 weeks of onset) with a well-fixed implant. It involves thorough debridement with exchange of modular components (polyethylene liner, femoral head). Success rates are 50 to 70% overall and higher with acute hematogenous infections by susceptible organisms. Organism-specific IV antibiotics are given for 6 weeks followed by oral suppressive therapy. DAIR is contraindicated when the implant is loose or the organism is highly resistant.
Two-Stage Exchange Arthroplasty
Two-stage exchange is the gold standard for chronic PJI, with eradication rates of 85 to 95%. The first stage involves explantation of all components and cement, thorough debridement, and placement of an antibiotic-loaded cement spacer (static or articulating, with articulating spacers preserving motion and facilitating reimplantation). An antibiotic holiday follows with reassessment of inflammatory markers. The second stage involves reimplantation after normalization of serologic markers and negative aspiration, typically 6 to 12 weeks later.
One-Stage Exchange Arthroplasty
One-stage exchange involves single-procedure explantation, debridement, and reimplantation. It is gaining popularity and requires identification of the infecting organism preoperatively, a susceptible pathogen, and adequate soft tissue coverage. Eradication rates approach 90% in carefully selected patients. Advantages include single anesthesia, shorter total treatment time, lower cost, and less functional impairment.
Chronic Suppression
Long-term oral antibiotic therapy without surgical intervention is reserved for patients who are not surgical candidates or who refuse surgery. Suppressive regimens typically include oral agents with good bioavailability such as trimethoprim-sulfamethoxazole or doxycycline. This does not eradicate infection; the goals are pain control and maintenance of function.
Salvage Procedures
Resection arthroplasty (Girdlestone) involves permanent removal of components without reimplantation, resulting in a flail limb. Arthrodesis may be considered for the knee when reimplantation is not feasible, providing a stable but stiff limb. Amputation is a last resort for refractory infection, sepsis, or limb-threatening soft tissue loss.
Prevention
Preoperative optimization includes nasal MRSA screening and decolonization, glycemic control (HbA1c below 8%), BMI optimization, smoking cessation, and nutritional status assessment. Perioperative antibiotics include a first-generation cephalosporin (cefazolin) within 60 minutes of incision, with vancomycin added for MRSA carriers. Intraoperative measures include laminar airflow, body exhaust suits, limiting OR traffic, and antibiotic-loaded cement in cemented fixation. Wound management requires careful soft tissue handling, layered closure, and monitoring for persistent drainage.
Clinical Pearls
A high index of suspicion is the first step in diagnosing PJI; any painful joint replacement should be aspirated before considering aseptic revision. Two positive cultures with the same organism or a draining sinus tract are definitive for PJI; a single culture result should not be relied upon. DAIR is only appropriate for acute infections with well-fixed components; chronic infections require exchange arthroplasty for reliable eradication. Two-stage exchange remains the gold standard for chronic PJI, but one-stage protocols are producing comparable results in selected patients at experienced centers.
References
- Parvizi J, Tan TL, Goswami K, et al. The 2018 definition of periprosthetic joint infection: an evidence-based and validated criteria. J Arthroplasty. 2018;33(5):1309-1314.
- Osmon DR, Berbari EF, Berendt AR, et al. Diagnosis and management of prosthetic joint infection: clinical practice guidelines by the IDSA. Clin Infect Dis. 2013;56(1):e1-e25.
- Kunutsor SK, Whitehouse MR, Blom AW, et al. One- and two-stage surgical revision of peri-prosthetic joint infection of the hip: a pooled individual participant data analysis. Eur J Epidemiol. 2018;33(10):933-946.
- Deirmengian C, Kardos K, Kilmartin P, et al. The alpha-defensin test for periprosthetic joint infection outperforms the leukocyte esterase test strip. Clin Orthop Relat Res. 2015;473(1):198-203.