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Scientific Articles   |    
The Natural Progression of Synovial Fluid White Blood-Cell Counts and the Percentage of Polymorphonuclear Cells After Primary Total Knee ArthroplastyA Multicenter Study
Christian P. Christensen, MD1; Hany Bedair, MD2; Craig J. Della Valle, MD3; Javad Parvizi, MD, FRCS4; Brian Schurko, BS5; Cale A. Jacobs, PhD1
1 Lexington Clinic, 1221 South Broadway Drive, Lexington, KY 40504. E-mail address for C.A. Jacobs: calejacobs@hotmail.com
2 Department of Orthopaedic Surgery, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114
3 Department of Orthopaedic Surgery, Rush University Medical Center, 1653 West Congress Parkway, Chicago, IL 60612
4 Department of Orthopaedic Surgery, Rothman Institute at Thomas Jefferson University, Sheridan Building, 10th Floor, 112 South 9th Street, Philadelphia, PA 19107
5 Tufts University School of Medicine, 145 Harrison Avenue, Boston, MA 02111
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Investigation performed at the Lexington Clinic, Lexington, Kentucky; Massachusetts General Hospital, Boston, Massachusetts; Rush University Medical Center, Chicago, Illinois; and Thomas Jefferson University, Philadelphia, Pennsylvania

A commentary by James P. Waddell, MD, FRCSC, is linked to the online version of this article at jbjs.org.



Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. One or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.

Copyright © 2013 by The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2013 Dec 04;95(23):2081-2087. doi: 10.2106/JBJS.L.01646
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Abstract

Background: 

Assessments of the synovial fluid white blood-cell (WBC) count and percentage of polymorphonuclear cells (PMNs) have been reported to be useful in the diagnosis of periprosthetic joint infection. The purpose of this multicenter retrospective study was to evaluate the natural progression of the synovial fluid WBC count, PMN percentage, and total neutrophil count in patients who underwent knee aspiration during the first two years after primary total knee arthroplasty and had no evidence of periprosthetic joint infection.

Methods: 

From April 1999 to March 2012, 571 patients who presented within the first two years after primary total knee arthroplasty underwent knee aspiration as part of an evaluation for periprosthetic joint infection. Patients were categorized into four groups on the basis of the number of days between surgery and arthrocentesis. The synovial fluid WBC count, PMN percentage, and total neutrophil count were compared among the four time periods with use of separate one-way analyses of variance and Tamhane post-hoc analyses.

Results: 

Four hundred and fifty-two samples not associated with a periprosthetic joint infection were adequate for analysis. The synovial fluid WBC count, PMN percentage, and total neutrophil count all decreased after the first ninety postoperative days. The synovial fluid WBC count showed an earlier return to a level similar to the two-year time point than the PMN percentage did. The mean total neutrophil count decreased from 2533.2 cells/μL during the first forty-five days to 649.0 cells/μL from forty-six to ninety days, 269.5 cells/μL from three months to one year, and 240.8 cells/μL from one to two years.

Conclusions: 

The synovial fluid WBC count and PMN percentage changed at different rates over the first two years after total knee arthroplasty, with the WBC count exhibiting an initially more rapid decrease and the PMN percentage demonstrating a more linear decrease. Hence, the total neutrophil count, which combines these two parameters, may provide a better method to identify patients with a periprosthetic joint infection. Values for the synovial fluid WBC count, PMN percentage, and total neutrophil count were all significantly elevated in the early postoperative period, and the use of standard cutoff values for the diagnosis of periprosthetic joint infection can lead to false-positive results.

Level of Evidence: 

Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

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    Accreditation Statement
    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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