title: Assessment of inter- and intra-observer reliability in the determination of radiographic version and inclination of the cup in metal-on-metal hip resurfacing.
abstract: OBJECTIVE
  Determination of the cup orientation after metal-on-metal hip resurfacing may provide important information in the postoperative follow-up. We present a mathematical method based on a previously described approach to assess the version and inclination of the cup in the metal-on-metal bearing without a separate software computation from plain radiographs. The aim of the study was to assess the intra- and inter-observer reliability of this method.
  
  
  METHODS
  Calculation of version and inclination were done twice for 20 hip resurfacings by four observers. Intra-observer reliability was estimated by mean error and correlation of the two sets of measurement for version and inclination. Bland-Altman plots, intra-class coefficient and mean error were used to assess the inter-observer reliability of the measurements.
  
  
  RESULTS
  Intra-observer correlation for version measurement ranged from 0.74 to 0.94. Correlation for inclination varied between 0.94 and 0.97. Upper and lower limits of agreement in Bland-Altman plots for version measurements between observers ranged from 4.1 to 7.2 degrees and from -3.2 to -8.3 degrees, respectively. For inclination measurements the upper and lower limits ranged from 3.1 to 5.3 degrees and from -2.7 to -6.0 degrees.
  
  
  CONCLUSIONS
  Mean errors, correlation coefficients and 95% limits of agreement were on an acceptable level. We believe that this method is applicable for clinical use.
authors.affiliation: Coxa Ltd, Hospital for Joint Replacement, Tampere, Finland. aleksi.reito@uta.fi
authors.forename: Aleksi
authors.initials: A
authors.lastname: Reito
authors.forename: Timo
authors.initials: T
authors.lastname: Puolakka
authors.forename: Antti
authors.initials: A
authors.lastname: Paakkala
authors.forename: Jorma
authors.initials: J
authors.lastname: Pajamäki
mesh_terms: D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000379:methods*; D017760:Bone Malalignment / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000209:etiology; D005260:Female; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D008297:Male; D015588:Observer Variation; D011183:Postoperative Complications; D017755:Prosthesis Fitting / Q000379:methods*; D012086:Reoperation; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed