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Published on: December 3, 2017
Synovial White Blood Cell Count and Differential to Predict Successful Infection Management in a Two-Stage Revision
Tejbir S Pannu1, Jesus M Villa1, Arturo Corces2
1Levitetz Department of Orthopaedic Surgery, Cleveland Clinic Florida, Weston, FL.
Background:
An array of synovial white blood cell (WBC) count and polymorphonuclear differential (PMN%) thresholds have been reported using 2013 Musculoskeletal Infection Society (MSIS) definition which has a poor accuracy to confirm infection control before reimplantation. The workgroup of MSIS recently developed a comprehensive definition of successful infection management. Our objectives were to determine optimal thresholds for WBC count and PMN% associated with reimplantation success based on this new MSIS definition and assess if values above these thresholds indicate decreased survival time.
Methods:
A retrospective review was conducted on a consecutive series of 133 two-stage hip/knee arthroplasties performed by 15 surgeons (2014-2020) at 2 institutions. All surgeries had a minimum follow-up of 1 year. The inclusion criteria included reporting of preoperative synovial fluid aspiration results. Thus, 88 were finally included. Surgical success was defined by MSIS outcome reporting tool (Tiers 1-4). Receiver operating characteristic curve analyses were performed to estimate optimal thresholds of WBC count and PMN%. A Kaplan-Meier survival analyses with log-rank test were performed.
Results:
With area under the curve of 0.65, synovial PMN% showed superior accuracy than WBC count (area under the curve = 0.52) in determining outcome of reimplantation. The optimal PMN% threshold (62%) demonstrated sensitivity of 57% and specificity of 77%. The calculated WBC count threshold (2,733/μL) showed poor sensitivity (21%) but high specificity (95%). There was a significant difference in failure-free survival (24 months) between the cases with WBC count higher vs lower than 2,733/μL (P = .002). This was also true for PMN% at 5 months postoperatively (P = .009).
Conclusion:
WBC count (2,733/μL) shows very high specificity to confirm successful reimplantation. Both WBC count and PMN% (62%) thresholds can significantly determine reimplantation survival.
Insights
New thresholds for synovial white blood cell (WBC) count and polymorphonuclear differential (PMN%) can predict reimplantation success after hip/knee arthroplasty. A PMN% threshold of 62% and WBC count of 2,733/μL significantly indicate successful outcomes.
Area of Science:
- Orthopedic Surgery
- Infectious Disease Management
- Biomarker Analysis
Background:
- The 2013 Musculoskeletal Infection Society (MSIS) definition has limitations in accurately assessing infection control before reimplantation surgery.
- A new, comprehensive MSIS definition for successful infection management has been developed.
Purpose of the Study:
- To establish optimal synovial white blood cell (WBC) count and polymorphonuclear differential (PMN%) thresholds for predicting reimplantation success.
- To evaluate if these thresholds correlate with decreased survival time.
Main Methods:
- Retrospective review of 88 two-stage hip/knee arthroplasties with preoperative synovial fluid analysis.
- Receiver operating characteristic (ROC) curve analysis to determine optimal WBC count and PMN% thresholds.
- Kaplan-Meier survival analysis to assess the impact of thresholds on reimplantation survival.
Main Results:
- Synovial PMN% (AUC=0.65) was more accurate than WBC count (AUC=0.52) in predicting reimplantation outcomes.
- Optimal thresholds: PMN% of 62% (sensitivity 57%, specificity 77%) and WBC count of 2,733/μL (sensitivity 21%, specificity 95%).
- Elevated WBC count (>2,733/μL) and PMN% (>62%) were significantly associated with decreased failure-free survival.
Conclusions:
- Synovial WBC count threshold of 2,733/μL demonstrates high specificity for confirming successful reimplantation.
- Both optimal WBC count and PMN% thresholds are significant predictors of reimplantation survival in arthroplasty surgery.
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