Microbiological diagnosis in revision of infected knee arthroplasties in Denmark

Abstract

Background: Revision of infected knee arthroplasties is associated with high failure rates (30–40%). An understanding of the microbiology is important to optimize treatment and outcome. We describe microbiological diagnostic practice and diagnosis in revision of infected knee arthroplasties.

Methods: One hundred and two partial revisions (open debridement and exchange of tibial insert) and 213 two-stage procedures performed due to infection in 275 patients from 1 July 2011 to 30 June 2013 were included and analysed by linkage to data from a nationwide registry on microbiological test results.

Results: 78 (24.8%) revisions were culture negative, 192 (60.9%) showed monomicrobial growth and 43 (14.3%) polymicrobial growth. Staphylococcus aureus was the most frequent isolate in mono-culture in 70 (22.2%) revisions and in polymicrobial culture in 15 revisions with a total frequency of 27.0%. Only one case (1.4%) of methicillin-resistance was registered. Coagulase-negative staphylococci (CoNS) were frequent, sole pathogen in 65 revisions and in polymicrobial cultures in 28 revisions with a total frequency of 29.5%. A pre-operative knee aspiration was performed in 50% and preoperative blood cultures were performed in 22% of cases. In 73% of the preoperative knee-aspirations bacteriological findings were fully or partially in accordance with intraoperative cultures. In 54% of the later re-revisions due to infection (treatment-failures) the cultured species differed from or was not detected at index revision surgery.

Conclusions: The 25% culture negative cases in combination with only 50% preoperative knee aspirations and prevailing high failure rates confirm the need for improvement of diagnostic practice and treatment of infected knee arthroplasties.

Keywords:

• Knee arthroplasty
• infection
• revision
• microbiology
• microbiological diagnosis

Acknowledgements

We thank all the Danish orthopaedic surgeons and secretaries who contributed with data to the Danish Knee Arthroplasty Register and Danish National Patient Register. Furthermore, we thank all departments of clinical microbiology for their contribution of data in MiBa.

Disclosure statement

The authors report no conflicts of interest.

Additional information

Funding

The study was sponsored by a grant from the Lundbeck Foundation (R25-A2702). The Lundbeck Foundation had no influence on any stage of the study process or on the manuscript.