RESUMO
PURPOSE: Unexpected positive intraoperative cultures (UPIC) found in revision total knee arthroplasty (TKA) are difficult to interpret. Management goes along with risks for both over- and undertreating a potential periprosthetic joint infection (PJI). The objective of this systematic review was to determine the prevalence of UPIC in revision TKA surgery, evaluate the diagnostic workup process and the postoperative treatment, and assess outcome regarding re-revision rates. METHODS: Evidence was gathered from Medline (PubMed) and Embase published from January 2000 until April 2021. Nine studies with data of UPIC in revision TKA and outcome after at least 2 years of follow-up were identified. RESULTS: The calculated prevalence of UPIC in aseptic knee revision surgery was 8.32%. However, the diagnostical approach differs as well as the used criteria to confirm PJI in presumed aseptic revision surgery. The work-up generally consists of a serum C-reactive protein and Erythrocyte Sedimentation Rate, joint fluid aspiration for culture and white blood cell count and formula, and radiographic imaging. Collection of intraoperative cultures is widely used, but inconsistent in sample amount and incubation time. Once a single UPIC is found, surgeons tend to treat it in different ways. Regarding re-revision rates, the weighted arithmetic mean in the included studies was 18.45% in the unsuspected PJI group compared to 2.94% in the aseptic group. There also seems to be a trend towards higher re-revision rates when a higher number of intraoperative cultures are positive. CONCLUSION: The interpretation of UPIC in revision TKA is of utmost importance since the decision whether to treat a UPIC as an unsuspected PJI has a major impact on implant survival and re-revision rate. Different criteria are used to differentiate between unsuspected PJI and contamination in true aseptic failure, and the heterogeneity amongst the included papers impedes to state a clear recommendation, integrating not only quantitative findings, but also qualitative data such as virulence of the identified microorganism. LEVEL OF EVIDENCE: Systematic review, III.