Variation of synovial fluid leucocyte cell count and polymorphonuclear percentage in patients with aseptic revision total knee arthroplasty

Michael Fuchs; Felix Kirchhoff; Heiko Reichel; Carsten Perka; Martin Faschingbauer; Clemens Gwinner

doi:10.1302/2633-1462.28.BJO-2021-0109

Variation of synovial fluid leucocyte cell count and polymorphonuclear percentage in patients with aseptic revision total knee arthroplasty

Bone Jt Open. 2021 Aug;2(8):566-572. doi: 10.1302/2633-1462.28.BJO-2021-0109.

Authors

Michael Fuchs¹, Felix Kirchhoff¹, Heiko Reichel¹, Carsten Perka², Martin Faschingbauer¹, Clemens Gwinner²

Affiliations

¹ RKU Department of Orthopaedic Surgery, University Ulm Medical Centre, Ulm, Baden-Württemberg, Germany.
² Department of Orthopaedic Surgery, Charite Universitatsmedizin Berlin, Berlin, Berlin, Germany.

Abstract

Aims: Current guidelines consider analyses of joint aspirates, including leucocyte cell count (LC) and polymorphonuclear percentage (PMN%) as a diagnostic mainstay of periprosthetic joint infection (PJI). It is unclear if these parameters are subject to a certain degree of variability over time. Therefore, the aim of this study was to evaluate the variation of LC and PMN% in patients with aseptic revision total knee arthroplasty (TKA).

Methods: We conducted a prospective, double-centre study of 40 patients with 40 knee joints. Patients underwent joint aspiration at two different time points with a maximum period of 120 days in between these interventions and without any events such as other joint aspirations or surgeries. The main indications for TKA revision surgery were aseptic implant loosening (n = 24) and joint instability (n = 11).

Results: Overall, 80 synovial fluid samples of 40 patients were analyzed. The average time period between the joint aspirations was 50 days (SD 32). There was a significantly higher percentage change in LC when compared to PMN% (44.1% (SD 28.6%) vs 27.3% (SD 23.7%); p = 0.003). When applying standard definition criteria, LC counts were found to skip back and forth between the two time points with exceeding the thresholds in up to 20% of cases, which was significantly more compared to PMN% for the European Bone and Joint Infection Society (EBJIS) criteria (p = 0.001), as well as for Musculoskeletal Infection Society (MSIS) (p = 0.029).

Conclusion: LC and PMN% are subject to considerable variation. According to its higher interindividual variance, LC evaluation might contribute to false-positive or false-negative results in PJI assessment. Single LC testing prior to TKA revision surgery seems to be insufficient to exclude PJI. On the basis of the obtained results, PMN% analyses overrule LC measurements with regard to a conclusive diagnostic algorithm. Cite this article: Bone Jt Open 2021;2(8):566-572.

Keywords: Joint Aspiration; Joint Infection; Musculoskeletal Infection; Periprosthetic Joint Infection; Periprosthetic joint infection (PJI); Synovial Analysis; Synovial fluid; Total Knee arthroplasty; White Blood Cell Count; aseptic revision total knee arthroplasty; implant loosening; joint aspirations; knee joints; leucocytes; revision surgery.