title: Reproducibility of measuring the shape and three-dimensional position of cervical vertebrae in upright position using the EOS stereoradiography system.
abstract: METHODS
  An interobserver and intraobserver reproducibility study of the use of EOS stereoradiography system at the cervical spine.
  
  
  OBJECTIVE
  To investigate reproducibility of the determination of the vertebral shape, position, and orientation of C3-C7 vertebrae in vivo using the EOS stereoradiography system.
  
  
  BACKGROUND
  Since CT and MRI 3-dimensional (3D) analysis of the spinal architecture are done in supine position, measurements of the relative position of the cervical vertebrae in vivo in standing position requires stereoradiography. The innovative EOS system is an accurate and promising tool for stereoradiography. Its reproducibility at the cervical spine had to be assessed.
  
  
  METHODS
  Twenty volunteers had biplanar radiographs of the cervical spine. C3-C7 were reconstructed by 2 observers, 2 times each. Each reconstruction was compared with the corresponding average object in term of shape (point-to-surface distance) and position (Tx, Ty, Tz, Rx, Ry, Rz in a local screw-frame).
  
  
  RESULTS
  The 95% confidence interval of the error in shape was 1.83 mm. It was 0.84 mm, 1.42 mm, 0.58 mm, 2.53 degrees, 2.34 degrees, and 3.24 degrees for the position in Tx, Ty, Tz, Rx, Ry, and Rz. Intraobserver differences were not significant. Interobserver differences were significant for the shape and in Tx, Rx, and Ry (0.9 mm, 0.54 mm, 0.33 degrees, and 0.28 degrees).
  
  
  CONCLUSIONS
  Overall reproducibility favorably compared with other imaging methods, whereas significant interobserver disagreements were narrow and partial.
authors.affiliation: Biomechanics Lab-Ecole Nationale Supérieure d'Arts et Métiers, Paris, France. marc-antoine.rousseau@psl.aphp.fr
authors.forename: Marc-Antoine
authors.initials: MA
authors.lastname: Rousseau
authors.forename: Sébastien
authors.initials: S
authors.lastname: Laporte
authors.forename: Estelle
authors.initials: E
authors.lastname: Chavary-Bernier
authors.forename: Jean-Yves
authors.initials: JY
authors.lastname: Lazennec
authors.forename: W
authors.initials: W
authors.lastname: Skalli
mesh_terms: D000328:Adult; D002574:Cervical Vertebrae / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000295:instrumentation*; D008297:Male; D015588:Observer Variation; D011187:Posture; D011859:Radiography / Q000295:instrumentation; D012016:Reference Values; D015203:Reproducibility of Results