Utility of synovial fluid aspirations in failed metal-on-metal total hip arthroplasty
Related Experiment Video
Updated: May 13, 2026
Novel Diagnostics in Revision Arthroplasty: Implant Sonication and Multiplex Polymerase Chain Reaction
Published on: December 3, 2017
Cody C Wyles1, Dirk R Larson, Matthew T Houdek
1Mayo Clinic, Rochester, Minnesota 55905, USA.
Abstract:
White blood cell (WBC) count and neutrophil percentage from preoperative synovial fluid aspirations are used to help determine the presence or absence of periprosthetic joint infection (PJI) in failed total hip arthroplasty (THA). The clinical levels indicative of infection have not been delineated in metal-on-metal (MoM) bearings. We identified 39 patients who received a preoperative synovial fluid aspiration prior to MoM revision. Thirty-five of 39 cases were culture negative and 4 of 39 were culture positive. WBC count >3000 cells/μL was 100% sensitive and 57.1% specific. Neutrophil percentage >80% was 100% sensitive and 97.1% specific. Both CRP and ESR >8.0mg/L and >22 mm/h, respectively were 75.0% sensitive and 67.6% specific. Our data suggest that synovial WBC count and serum ESR and CRP have poor predictive value in diagnosing PJI for failed MoM THA, whereas synovial neutrophil percentage is a highly accurate marker for diagnosing infection in this patient population.
Insights
Diagnosing periprosthetic joint infection (PJI) in metal-on-metal total hip arthroplasty (THA) is challenging. Synovial neutrophil percentage is a highly accurate marker for infection, unlike WBC count or inflammatory markers.
Area of Science:
- Orthopedic Surgery
- Infectious Disease
- Biomarkers
Background:
- Periprosthetic joint infection (PJI) is a significant complication following total hip arthroplasty (THA).
- Accurate diagnosis of PJI in metal-on-metal (MoM) bearing THA is crucial for revision surgery.
- Established diagnostic criteria for PJI may not directly apply to MoM bearings.
Purpose of the Study:
- To evaluate the diagnostic utility of synovial fluid white blood cell (WBC) count and neutrophil percentage in identifying PJI in failed MoM THA.
- To compare the sensitivity and specificity of synovial fluid markers with serum inflammatory markers (CRP and ESR) for PJI diagnosis in this specific patient group.
Main Methods:
- Retrospective analysis of 39 patients undergoing MoM THA revision with preoperative synovial fluid aspiration.
- Analysis of synovial fluid WBC count, neutrophil percentage, and serum C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR).
- Calculation of sensitivity and specificity for each marker in diagnosing culture-proven or clinically suspected PJI.
Main Results:
- Synovial WBC count >3000 cells/μL showed 100% sensitivity but only 57.1% specificity.
- Synovial neutrophil percentage >80% demonstrated 100% sensitivity and 97.1% specificity.
- Serum CRP and ESR levels had lower sensitivity (75.0%) and specificity (67.6%) for PJI diagnosis.
Conclusions:
- Synovial fluid neutrophil percentage is a highly accurate and reliable biomarker for diagnosing PJI in failed MoM THA.
- Synovial WBC count and serum inflammatory markers (CRP, ESR) have limited predictive value in this specific patient population.
- Neutrophil percentage in synovial fluid offers superior diagnostic performance compared to other commonly used markers for PJI in MoM THA.
