Discordance between preoperative synovial fluid cultures and intraoperative cultures occurred in a high proportion of patients undergoing revision arthroplasty for periprosthetic joint infection, according to a recent study.
In an international multicenter retrospective observational cohort study, conducted across 16 hospitals in 10 countries, investigators included 647 patients with periprosthetic joint infection who underwent septic total revision hip or knee arthroplasty between January 2020 and January 2024. All of the patients had a positive preoperative synovial fluid culture, which was compared with intraoperative cultures obtained during surgery.
Discordance—defined as any mismatch in microorganisms between preoperative and intraoperative cultures—was observed in 36% (n - 230) of the cases, including 26% (n = 170) with partial discordance. The strongest association was center-specific variation, with one site showing more than twice the rate of discordance compared with other centers.
Clinical factors were also associated with discordance. Patients undergoing hip arthroplasty had about 1.6 times the odds of discordance compared with knee procedures, and patients with a sinus tract had about 1.8 times the odds. Other evaluated factors, including obesity, prior antibiotic use, and microorganisms considered potential contaminants weren't independently associated with discordance.
In a multivariate analysis excluding the high-discordance center, the presence of a sinus tract remained independently associated with discordance. The investigators noted that sinus tracts may be associated with polymicrobial periprosthetic joint infection, which could contribute to mismatched culture results.
The findings may reflect differences in local microbiological practices, including sample handling and processing. The investigators noted that hip joint aspiration may be technically more difficult compared with knee aspiration, which could have affected the sample reliability.
The study had several limitations, including its retrospective design, missing data for key variables such as synovial fluid cytology, and the disproportionate influence of one high-volume center. The lack of detailed demographic data may also have limited generalizability.
Overall, the findings suggested that preoperative synovial fluid cultures may not consistently reflect intraoperative microbiology and should be interpreted alongside clinical context and institutional patterns.
“Our findings highlight the need for centers to be aware of their own discordance rates and underscores the importance of exercising caution in patients with hip arthroplasty and/or a sinus tract undergoing septic revision surgery," wrote lead study author Karsten D. Ottink, MD, of the Department of Medical Microbiology and Infection Prevention at the University Medical Center Groningen at the University of Groningen in the Netherlands, and colleagues. "Awareness of these risk factors for discordance may help optimize perioperative management, select empirical or targeted antibiotic therapy, and improve patient outcomes in [periprosthetic join infection]," they concluded.
Full disclosures of the study authros can be found in the study.
Source: JBJS Open Access
