title: Accuracy and reliability of different methods to evaluate the acetabular cup version from plain radiographs.
abstract: OBJECTIVE
  The purpose of this study was to compare different methods of evaluating the version of a metallic acetabular cup from plain radiographs and to compare them regarding their accuracy, inter- and intra-observer reliability.
  
  
  METHODS
  Conventional anterior-posterior radiographs were taken of a phantom-model at different defined ante- and retroversion angles of the acetabular cup. The version angles of the acetabular cup were derived according to four different established methods from the radiographs by five independent examiners.
  
  
  RESULTS
  We were able to determine the radiographic version with the greatest accuracy according to a modified technique of Pettersson et al. Furthermore, we found the highest intra- and inter-observer reliability using this technique.
  
  
  CONCLUSIONS
  A modified technique of Pettersson et al. broadens the spectrum of applicability for the radiographic evaluation of the version angle of metal-backed acetabular cups in comparison to the originally introduced method. In clinical practice, however, the significance of deriving the cup position from standard radiographs should not be over-estimated and therefore a computed tomography should be performed in certain critical cases.
authors.affiliation: Orthopädische Klinik und Poliklinik, Universität Rostock, Doberaner Str. 142, 18057 Rostock, Germany. maximilian.haenle@med.uni-rostock.de
authors.forename: Maximilian
authors.initials: M
authors.lastname: Haenle
authors.forename: Wolfram
authors.initials: W
authors.lastname: Mittelmeier
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Barbano
authors.forename: Klaus
authors.initials: K
authors.lastname: Wörtler
authors.forename: Roger
authors.initials: R
authors.lastname: Scholz
authors.forename: Rainer
authors.initials: R
authors.lastname: Bader
mesh_terms: D006621:Hip Joint / Q000000981:diagnostic imaging*; D006622:Hip Prosthesis; D006801:Humans; D015588:Observer Variation; D011859:Radiography