title: Comparison of 2D radiography and a semi-automatic CT-based 3D method for measuring change in dorsal angulation over time in distal radius fractures.
abstract: OBJECTIVE
  The aim of the present study was to compare the reliability and agreement between a computer tomography-based method (CT) and digitalised 2D radiographs (XR) when measuring change in dorsal angulation over time in distal radius fractures.
  
  
  METHODS
  Radiographs from 33 distal radius fractures treated with external fixation were retrospectively analysed. All fractures had been examined using both XR and CT at six times over 6 months postoperatively. The changes in dorsal angulation between the first reference images and the following examinations in every patient were calculated from 133 follow-up measurements by two assessors and repeated at two different time points. The measurements were analysed using Bland-Altman plots, comparing intra- and inter-observer agreement within and between XR and CT.
  
  
  RESULTS
  The mean differences in intra- and inter-observer measurements for XR, CT, and between XR and CT were close to zero, implying equal validity. The average intra- and inter-observer limits of agreement for XR, CT, and between XR and CT were ± 4.4°, ± 1.9° and ± 6.8° respectively.
  
  
  CONCLUSIONS
  For scientific purpose, the reliability of XR seems unacceptably low when measuring changes in dorsal angulation in distal radius fractures, whereas the reliability for the semi-automatic CT-based method was higher and is therefore preferable when a more precise method is requested.
authors.affiliation: Department of Orthopaedics, Uppsala University, S-751 85, Uppsala, Sweden. albert.christersson@akademiska.se.
authors.forename: Albert
authors.initials: A
authors.lastname: Christersson
authors.affiliation: Centre for Image Analysis, Uppsala University, Uppsala, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Nysjö
authors.affiliation: Uppsala Clinical Research Centre, UCR Statistics, Uppsala University, Uppsala, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Berglund
authors.affiliation: Centre for Image Analysis, Uppsala University, Uppsala, Sweden.
authors.forename: Filip
authors.initials: F
authors.lastname: Malmberg
authors.affiliation: Centre for Image Analysis, Uppsala University, Uppsala, Sweden.
authors.forename: Ida-Maria
authors.initials: IM
authors.lastname: Sintorn
authors.affiliation: Centre for Image Analysis, Uppsala University, Uppsala, Sweden.
authors.forename: Ingela
authors.initials: I
authors.lastname: Nyström
authors.affiliation: Department of Orthopaedics, Uppsala University, S-751 85, Uppsala, Sweden.
authors.forename: Sune
authors.initials: S
authors.lastname: Larsson
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005593:Fracture Fixation, Internal; D017759:Fractures, Malunited / Q000000981:diagnostic imaging* / Q000628:therapy; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000295:instrumentation*; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D010363:Pattern Recognition, Automated; D011857:Radiographic Image Interpretation, Computer-Assisted; D011885:Radius Fractures / Q000000981:diagnostic imaging*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D014954:Wrist Injuries / Q000000981:diagnostic imaging* / Q000628:therapy; D014962:X-Ray Film
keywords: Agreement; Computed tomography; Conventional radiography; Distal radius fracture; Dorsal angulation; Radiography; Reliability