This Article Full Text Full Text (PDF) Submit a response View responses Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal My Folders Download to citation manager Google Scholar Articles by Fink, B. Articles by Frommelt, L. PubMed PubMed Citation Articles by Fink, B. Articles by Frommelt, L.

The value of synovial biopsy, joint aspiration and C-reactive protein in the diagnosis of late peri-prosthetic infection of total knee replacements

¹ Department of Joint Replacement, General and Rheumatic Orthopaedics Orthopaedic Clinic, Markgröningen, Kurt-Lindemann-Weg 10, 71706 Markgröningen, Germany.
² Orthopaedic Department Rheumaklinik Bad Bramstedt, University of Hamburg-Eppendorf, Oskar-Alexander-Strasse 26, 24576 Bad Bramstedt, Germany.
³ Institute of Pathology, Klinikum Kassel, Mönchebergstrasse 41-43, 34125 Kassel, Germany.
⁴ Joint Practice of Laboratory Medicine Ludwigsburg, Wernerstrasse 33, 71636 Ludwigsburg, Germany.
⁵ Service of Infectious Diseases, Clinical Microbiology and Infection Control, ENDO-Klinik, Holstenstrasse 2, 22767 Hamburg, Germany.

Correspondence should be sent to Professor B. Fink; e-mail: b.fink{at}okm.de

We analysed the serum C-reactive protein level, synovial fluid obtained by joint aspiration and five synovial biopsies from 145 knee replacements prior to revision to assess the value of these parameters in diagnosing late peri-prosthetic infection. Five further synovial biopsies were used for histological analysis. Samples were also obtained during the revision and incubated and analysed in an identical manner for 14 days.

A total of 40 total knee replacements were found to be infected (prevalence 27.6%). The aspiration technique had a sensitivity of 72.5% (95% confidence interval (CI) 58.7 to 86.3), a specificity of 95.2% (95% CI 91.2 to 99.2), a positive predictive value of 85.3% (95% CI 73.4 to 100), a negative predictive value of 90.1% (95% CI 84.5 to 95.7) and an accuracy of 89%. The biopsy technique had a sensitivity of 100%, a specificity of 98.1% (95% CI 95.5 to 100), a positive predictive value of 95.2% (95% CI 88.8 to 100), a negative predictive value of 100% and an accuracy of 98.6%. C-reactive protein with a cut-off-point of 13.5 mg/l had a sensitivity of 72.5% (95% CI 58.7 to 86.3), a specificity of 80.9% (95% CI 73.4 to 88.4), a positive predictive value of 59.2% (95% CI 45.4 to 73.0), a negative predictive value of 88.5% (95% 81.0 to 96.0 CI) and an accuracy of 78.1%.

We found that biopsy was superior to joint aspiration and C-reactive protein in the diagnosis of late peri-prosthetic infection of total knee replacements.

eLetters: