title: Comparison of digital and conventional radiostereometric image analysis in an ankle phantom model.
abstract: OBJECTIVE
  Radiostereometric analysis (RSA) allows accurate three-dimensional measurements of micromotion in skeletal structures. The current RSA techniques are based on the analysis of scanned plain films. This study was undertaken to compare digital filmless RSA technique to conventional scanning technique using a phantom model of the ankle mortise.
  
  
  METHODS
  In the first experiment, the relative displacement of the markers inserted to the fibula in relation to the markers inserted to the tibia was studied by means of double examinations and the precision of DICOM images were compared to scanned images of printed radiographs. In the second experiment, the film pair of double examination was re-imported or re-scanned and self-compared in order to show merely the error related to the image processing.
  
  
  RESULTS
  The precision of RSA using scanned images of printed radiographs was compatible to DICOM images. However, the mean error of rigid body fitting (ME) values were significantly lower in use of DICOM images compared with scanned radiographs, indicating less deformation of rigid body segments in filmless analysis.
  
  
  CONCLUSIONS
  Precision of the RSA method was improved under the completely filmless environment. Therefore, this technique can be recommended for clinical studies of radiostereometric analysis.
authors.affiliation: Orthopaedic Research Unit, Department of Orthopaedic Surgery and Traumatology, University of Turku, Turku, Finland.
authors.forename: T J
authors.initials: TJ
authors.lastname: Mäkinen
authors.forename: K T
authors.initials: KT
authors.lastname: Mattila
authors.forename: H
authors.initials: H
authors.lastname: Määttänen
authors.forename: H T
authors.initials: HT
authors.lastname: Aro
mesh_terms: D000843:Ankle Joint / Q000000981:diagnostic imaging*; D005360:Fibula / Q000000981:diagnostic imaging; D006801:Humans; D021621:Imaging, Three-Dimensional; D008953:Models, Anatomic; D019047:Phantoms, Imaging; D010780:Photogrammetry / Q000379:methods*; D011859:Radiography; D013977:Tibia / Q000000981:diagnostic imaging