• Taner Karlidag, Luigi Zanna, Giacomo Traverso, Min-Jae Lee, Thorsten Gehrke, and Mustafa Citak.
• Department of Orthopedics and Traumatology, Helios ENDO-Klinik Hamburg, Holstenstr. 2, 22767, Hamburg, Germany.
• Arch Orthop Trauma Surg. 2024 Dec 12; 145 (1): 2525.

PurposeThe diagnostic challenges of periprosthetic joint infection (PJI) for orthopedic surgeons are significant. Prior research has indicated that patients with adverse reactions, dislocations, and aseptic loosening exhibit a heightened count of white blood cells (WBC) in their synovial fluid, along with an increased polymorphonuclear cell percentage (PMN%). The prevalence of false-positive results raises concerns about the reliability of these tools in distinguishing aseptic failure from PJI.MethodsWe have performed a retrospective inquiry of the medical records of all patients who have undergone aseptic revision total knee arthroplasty (TKA) at our tertiary referral arthroplasty center. We conducted an assessment on 552 knees by applying the guidelines set forth by the 2018 International Consensus Meeting. Recorded preoperative parameters: aspiration results (WBC, PMN%, and AD immunoassay), preoperative and intraoperative diagnoses, microbiologic and histopathologic findings from periprosthetic tissue samples, and prosthetic details.ResultsAmong the causes of aseptic revision investigated, patients with polyethylene wear exhibited the highest median WBC count (median 1091 cells/µL, range 83.5-1715.5 cells/µL; p = 0.010). Concerning periprosthetic conditions, patients with wear-induced synovitis exhibited a significantly higher synovial fluid WBC count (median 1093 cells/µL, range 587-1683 cells/µL; p < 0.001). Among all the reasons for failure, periprosthetic fractures had the greatest percentage of WBC counts surpassing 3000 cells/µL (18.1% [2 of 11]; p = 0.006).ConclusionOur study has uncovered significant variations in WBC count during aseptic revision TKA when utilizing automated cell counting. Therefore, to optimize diagnostic accuracy in synovial aspiration during aseptic revision TKA, it is advisable to employ a combination of WBC count and PMN%, along with manual counting techniques or AD, depending on the specific clinical scenario.Level Of EvidenceIII.© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

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