Analysis of serological markers and synovial fluid cytology in aseptic revision total knee arthroplasty

Abstract

Background and aim

Recent studies examining synovial fluid analysis to differentiate causes for aseptic revision total knee arthroplasty (rTKA) were limited to aseptic loosening and instability. This study aims to establish specific serological and synovial profiles for various rTKA etiologies.

Methods

We retrospectively reviewed patients who underwent aseptic rTKA at a single academic institution between 2012 and 2023. Inclusion required complete serum inflammatory markers (erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)) and synovial fluid differentials within three months pre-operatively. Periprosthetic joint infections were strictly excluded utilizing the 2018 International Consensus Meeting criteria. In total, 156 patients were included and stratified into five aseptic etiologies: aseptic loosening (50.6%), instability (28.2%), arthrofibrosis (16.7%), liner wear (2.6%), and component malposition (1.9%). Serological markers were evaluated utilizing a multivariate general linear model adjusting for patient demographics, while synovial markers were assessed via Welch’s Analysis of Variance (ANOVA) and Games-Howell post-hoc testing.

Results

Multivariate analysis demonstrated that the underlying rTKA indication was not a significant independent predictor of elevated ESR (P = 0.661) or CRP (P = 0.947). Welch’s ANOVA revealed significant differences in the percentage of synovial monocytes (P < 0.001) and lymphocytes (P = 0.010), alongside the polymorphonuclear cells/monocyte (P = 0.030) and lymphocyte/monocyte (P = 0.005) ratios. Games-Howell post-hoc testing demonstrated the tibial liner wear group exhibited significantly higher monocyte percentages, paired with lower lymphocyte percentages and cellular ratios, compared to other aseptic etiologies.

Conclusions

This study revealed that routine systemic inflammatory markers and standard synovial fluid cell counts do not significantly vary among the common etiologies of aseptic rTKA. Nonetheless, tibial polyethylene liner wear appears to elicit an exploratory, monocyte-predominant and lymphocyte-depleted local macrophage response that is absent in other mechanisms of aseptic failure. Further research with larger cohorts is warranted to validate this association and explore its potential as a diagnostic tool.