Synovial Fluid Viscosity Test Is Promising for the Diagnosis of Periprosthetic Joint Infection

Abstract Background So far there is no “gold standard” test for the diagnosis of periprosthetic joint infection (PJI), compelling clinicians to rely on several serological and synovial fluid tests with no 100% accuracy. Synovial fluid viscosity is one of the parameters defining the rheology properties of synovial fluid. We hypothesized that patients with PJI may have a different level of synovial fluid viscosity and aimed to investigate the sensitivity and specificity of synovial fluid viscosity in detecting PJI. Methods This prospective study was initiated to enroll patients undergoing primary and revision arthroplasty. Our cohort consisted of 45 patients undergoing revision for PJI (n=15), revision for aseptic failure (n=15), and primary arthroplasty (n=15). PJI was defined using the Musculoskeletal Infection Society criteria. In all patients, synovial fluid viscosity, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and plasma D-dimer level were measured preoperatively. Results The synovial fluid viscosity level was significantly lower (p=0.0011) in the patients with PJI (7.93 mPa·s [range, 3.0 to 15.0 mPa·s]) than for patients with aseptic failure (13.11 mPa·s [range, 6.3 to 20.4 mPa·s]). Using the Youden index, 11.80 mPa·s was determined as the optimal threshold value for synovial fluid viscosity for the diagnosis of PJI. Synovial fluid viscosity outperformed CRP, ESR and plasma D-dimer, with a sensitivity of 93.33% and a specificity of 66.67%. Conclusion Synovial fluid viscosity seems to be on the same level of accuracy with CRP, ESR and D-dimer regarding PJI detection and to be a promising marker for the diagnosis of PJI.