Laboratory Value Effectiveness in Predicting Early Postoperative Periprosthetic Joint Infection after Total Hip Arthroplasty

Abstract Introduction Diagnosing early periprosthetic joint infection (PJI) after primary total hip arthroplasty (THA) remains challenging. We sought to validate optimal laboratory value cutoffs for detecting early PJIs in a series of primary THAs from one institution. Methods We retrospectively identified 22,795 primary THAs performed between 2000 and 2019. Within 12 weeks, 43 hips (43 patients) underwent arthrocentesis. Patients were divided into two groups: evaluation ≤6 weeks or 6-12 weeks following THA. The 2011 Musculoskeletal Infection Society (MSIS) major criteria for PJI diagnosed PJI in 15 patients. Mann-Whitney U tests were used to compare median laboratory values and receiver operator curve (ROC) analysis was used to evaluate optimal cutoff values. Results Both within 6 weeks and between 6-12 weeks postoperatively, median C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), synovial white blood cell (WBC) count, neutrophil percentage, and absolute neutrophil count (ANC) values were significantly higher in infected THAs. Optimal cutoffs within 6 weeks were: CRP ≥100 mg/L, synovial WBCs ≥4390 cells/μL, neutrophil percentage ≥74%, and ANC ≥3249 cells/μL. Between 6-12 weeks, optimal cutoffs were: CRP ≥33 mg/L, synovial WBCs ≥26,995 cells/μL, neutrophil percentage ≥93% and ANC ≥25,645 cells/μL. Conclusion Early PJI following THA should be suspected within 6 weeks with CRP ≥100 mg/L or synovial WBCs ≥4390 cells/μL. Between 6-12 weeks postoperatively, cutoffs of CRP ≥33 mg/L, synovial fluid WBC of ≥26,995 cells/μL, and neutrophil percentage of ≥93% diagnosed PJI with high accuracy.