OUTCOMES OF FUNGAL VERSUS BACTERIAL PERIPROSTHETIC JOINT INFECTIONS AFTER TOTAL HIP AND KNEE ARTHROPLASTY: RETROSPECTIVE COHORT ANALYSIS OF 461 CASES

Periprosthetic joint infection (PJI) is a rare but severe complication following total hip arthroplasty (THA) and total knee arthroplasty (TKA). Bacterial pathogens account for most cases, while fungal PJIs represent approximately 1% and remain poorly characterized. The lack of direct and comparative studies between bacterial and fungal PJI makes it difficult to draw clear conclusions about differences in treatment outcomes, complication rates, and optimal management strategies. As a result, clinical decision-making for fungal PJIs is often extrapolated from bacterial PJI protocols, despite significant microbiologic differences. Aim This study compared outcomes of bacterial and fungal PJIs managed at a tertiary referral center. Methods We conducted a retrospective review of culture-proven bacterial and fungal PJIs involving THA or TKA at a single institution between January 2015 and February 2025. Diagnosis was based on Musculoskeletal Infection Society (MSIS) criteria. Demographics, comorbidities, infection chronicity, surgical strategy, and outcomes were collected. Treatment success was defined according to international Delphi consensus criteria. Univariate and multivariable logistic regression were performed to identify predictors of outcome. A total of 461 patients met inclusion criteria, including 402 bacterial and 59 fungal PJIs. Age, sex, and comorbidity profiles were similar between groups. Results Despite the similar baseline demographics, fungal infections more frequently presented as chronic (71% vs 52%, P = 0.013). In bivariate analysis, overall treatment success was significantly lower in fungal PJIs (22% vs 62%; OR 0.17 95% CI [0.09,0.33], P < 0.001). Mortality was higher in fungal infections (27% vs 11%; 2.97, [1.50,5.76], P = 0.002). Multivariable analysis identified fungal etiology, older age, higher Charlson Comorbidity Index, and current smoking as independent predictors for lower odds of success. When comparing treatment success by different surgical modalities, DAIR was particularly ineffective in fungal PJIs. Many of these DAIR procedures occurred before a fungal organism was identified. The prolonged incubation time required for fungal cultures delays definitive pathogen identification. Not only do fungal cultures take significantly longer to result, but there is significantly lower sensitivity compared to bacterial cultures. Thus, a DAIR procedure may be undertaken before fungal etiology is known, inadvertently applying a strategy that is ill- suited for fungal infections and contributing to their high failure rate. Conclusion Fungal PJIs are associated with markedly worse outcomes and higher mortality compared with bacterial infections. These findings emphasize the need for pathogen- specific surgical strategies, optimization of host comorbidities, and multicenter collaboration to standardize management of fungal PJIs.