title: Low rate of infected knee replacements in a nationwide series--is it an underestimate?
abstract: OBJECTIVE
  Specialist hospitals have reported an incidence of early deep infections of < 1% following primary knee replacement. The purpose of this study was to estimate the infection rate in a nationwide series using register-based data.
  
  
  METHODS
  The Finnish Arthroplasty Register (FAR) was searched for primary unicompartmental, total, and revision knee arthroplasties performed in 1997 through 2003 and eventual revision arthroplasties. The FAR data on revision arthroplasties was supplemented by a search of the national Hospital Discharge Register (HDR) for debridements, partial and total revision knee replacements, resection arthroplasties, arthrodeses, and amputations.
  
  
  RESULTS
  During the first postoperative year, 0.33% (95% CI: 0.13-0.84), 0.52% (0.45-0.60) and 1.91% (1.40-2.61) of the primary UKAs, primary TKAs, and revision TKAs, respectively, were reoperated due to infection. The 1-year rate of reoperations due to infection remained constant in all arthroplasty groups over the observation period. The overall infection rate calculated using FAR data only was 0.77% (95% CI: 0.69-0.86), which was lower, but was not, however, statistically significantly different from the overall infection rate calculated using endpoint data combined from FAR and HDR records (0.89%; 95% CI: 0.80-0.99). FAR registered revision arthroplasties and patellar resurfacing arthroplasties reliably but missed a considerable proportion of other reoperations.
  
  
  CONCLUSIONS
  More reoperations performed due to infection can be expected as the numbers of knee arthroplasties increase, since there has been no improvement in the early infection rate. Finnish Arthroplasty Register data appear to underestimate the incidence of reoperations performed due to infection.
authors.affiliation: Medical school, University of Tampere, Tampere, Finland.
authors.forename: Esa
authors.initials: E
authors.lastname: Jämsen
authors.forename: Kaisa
authors.initials: K
authors.lastname: Huotari
authors.forename: Heini
authors.initials: H
authors.lastname: Huhtala
authors.forename: Juha
authors.initials: J
authors.lastname: Nevalainen
authors.forename: Yrjö T
authors.initials: YT
authors.lastname: Konttinen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects* / Q000379:methods; D005260:Female; D005387:Finland / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D007720:Knee Prosthesis / Q000009:adverse effects; D008297:Male; D008875:Middle Aged; D011475:Prosthesis Failure; D016459:Prosthesis-Related Infections / Q000453:epidemiology* / Q000209:etiology; D012042:Registries; D012086:Reoperation; D055815:Young Adult