title: The reasons for knee arthroplasty revisions are incomparable in the different arthroplasty registries.
abstract: BACKGROUND
  The arthroplasty registries report the survivorship of knee arthroplasties and the reasons for revisions. The various registries report similar implant survivorships. However, the reasons for the knee revisions have not been compared. The aims of this study were to assess the reasons for knee arthroplasty revisions from the five valid arthroplasty registries and to evaluate whether the reasons for revisions in each registry were similar.
  
  
  METHODS
  The reported reasons for knee arthroplasty revisions were extracted from the arthroplasty registries of Australia, New Zealand, Norway, Sweden, and the National Joint Registry for England and Wales. The relevant data were identified from each arthroplasty registry's annual reports.
  
  
  RESULTS
  All the arthroplasty registries collected data for each performed knee arthroplasty revision using a specific form. The information provided by the registries varied. The numbers of different variables for the revisions were wide-ranging (from 8-33). In addition to the different variables, the reported percentages between the registries had an extremely wide variation.
  
  
  CONCLUSIONS
  The reasons for knee arthroplasty revisions are categorized differently in various arthroplasty registries, and there is a wide range of percentages presented. The differences in percentages may not be fully explained by the different outcome results in the different countries. The heterogeneity of the registries may guide the recording of the reasons behind the revisions. There is a definite need to standardize the structure of the arthroplasty registries, and to validate the data therein. A larger collaboration between the registries is essential.
authors.affiliation: Department of Surgery, Oulu University Hospital, Oulu, Box 29, Oulu, Finland. Electronic address: tuukka.niinimaki@fimnet.fi.
authors.forename: Tuukka T
authors.initials: TT
authors.lastname: Niinimäki
mesh_terms: D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D006801:Humans; D007720:Knee Prosthesis; D011475:Prosthesis Failure; D012042:Registries; D012086:Reoperation; D016896:Treatment Outcome
keywords: Failure; Knee arthroplasty; Registry; Revision