title: Reliability of classification for post-traumatic ankle osteoarthritis.
abstract: OBJECTIVE
  The purpose of this study was to identify the most reliable classification system for clinical outcome studies to categorize post-traumatic-fracture-osteoarthritis.
  
  
  METHODS
  A total of 118 orthopaedic surgeons and residents-gathered in the Ankle Platform Study Collaborative Science of Variation Group-evaluated 128 anteroposterior and lateral radiographs of patients after a bi- or trimalleolar ankle fracture on a Web-based platform in order to rate post-traumatic osteoarthritis according to the classification systems coined by (1) van Dijk, (2) Kellgren, and (3) Takakura. Reliability was evaluated with the use of the Siegel and Castellan's multirater kappa measure. Differences between classification systems were compared using the two-sample Z-test.
  
  
  RESULTS
  Interobserver agreement of surgeons who participated in the survey was fair for the van Dijk osteoarthritis scale (k = 0.24), and poor for the Takakura (k = 0.19) and the Kellgren systems (k = 0.18) according to the categorical rating of Landis and Koch. This difference in one categorical rating was found to be significant (p < 0.001, CI 0.046-0.053) with the high numbers of observers and cases available.
  
  
  CONCLUSIONS
  This study documents fair interobserver agreement for the van Dijk osteoarthritis scale, and poor interobserver agreement for the Takakura and Kellgren osteoarthritis classification systems. Because of the low interobserver agreement for the van Dijk, Kellgren, and Takakura classification systems, those systems cannot be used for clinical decision-making.
  
  
  METHODS
  Development of diagnostic criteria on basis of consecutive patients, Level II.
authors.affiliation: Orthopaedic Hand and Upper Extremity Service, Yawkey Centre, Massachusetts General Hospital, Harvard Medical School and University of Amsterdam Medical School, 55 Fruit Street, Boston, MA, 02114, USA. femke__claessen@hotmail.com.
authors.forename: Femke M A P
authors.initials: FM
authors.lastname: Claessen
authors.affiliation: Orthotrauma Research Centre Amsterdam, Academic Medical Centre Amsterdam, Amsterdam, The Netherlands.
authors.forename: Diederik T
authors.initials: DT
authors.lastname: Meijer
authors.affiliation: Orthopaedic Surgeon, Shoulder and Elbow Unit, Onze Lieve Vrouwe Gasthuis, Amsterdam, The Netherlands.
authors.forename: Michel P J
authors.initials: MP
authors.lastname: van den Bekerom
authors.affiliation: Orthotrauma Research Centre Amsterdam, Academic Medical Centre Amsterdam, Amsterdam, The Netherlands.
authors.forename: Barend D J
authors.initials: BD
authors.lastname: Gevers Deynoot
authors.affiliation: Orthotrauma Research Centre Amsterdam, Academic Medical Centre Amsterdam, Amsterdam, The Netherlands.
authors.forename: Wouter H
authors.initials: WH
authors.lastname: Mallee
authors.affiliation: Orthotrauma Research Centre Amsterdam, Academic Medical Centre Amsterdam, Amsterdam, The Netherlands.
authors.forename: Job N
authors.initials: JN
authors.lastname: Doornberg
authors.affiliation: Department of Orthopaedic Surgery, Academic Medical Centre Amsterdam, Amsterdam, The Netherlands.
authors.forename: C Niek
authors.initials: CN
authors.lastname: van Dijk
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D064386:Ankle Fractures / Q000150:complications*; D000843:Ankle Joint / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D010003:Osteoarthritis / Q000145:classification* / Q000000981:diagnostic imaging* / Q000209:etiology; D015203:Reproducibility of Results; D055815:Young Adult
keywords: Ankle trauma; Classification system; Interobserver study; Post-traumatic ankle fracture osteoarthritis