title: Inter-observer agreement of CT measurement of the glenoid bone surface by the CT Pico method: Comparison with laser in a cadaveric model.
abstract: OBJECTIVE
  The aim of this study was to test reproducibility of the CT Pico method in a cadaveric model and to compare CT Pico measurements with a high-precision laser probe for optical scanning.
  
  
  METHODS
  The glenoid surface of ten dried cadaveric scapulae (with intact surface) was measured by and high-precision laser probe for optical scanning, the latter being assumed as a reference standard. Measurements were done according to the Pico technique, using a circle-shaped region of interest (ROI) that was placed on the inferior glenoid rim. Measurements obtained using the CT Pico method (three readers) and with laser were compared to assess differences between radiological assessment and the reference standard. Each observer performed two repeated measurements from each scapulae (20 for each observer).
  
  
  RESULTS
  Mean differences between laser measurements and each CT reader were 18.4% (range, -4 to 61%) for reader 1, 12.4% (range, -15 to 64%) for reader 2, and 11% (range, -14 to 58%) for reader 3. Considering all the 60 measurements made by the three readers, 39 measurements out of 60 (65%) were outside the range [-5%; +5%] while 26 measurements (43%) are outside the range [-10%; +10%]. The largest differences (positive and negative) were +64 and -14 %, respectively. Intra-operator reproducibility was high in most cases (intraclass correlation coefficient (ICC) =0.93, ICC = 0.91, ICC = 0.93 and Lin's Concordance correlation coefficient (CCC) = 0.92, CCC = 0.90, CCC = 0.92 for reader 1 to 3, respectively. However, in five cases the CT Pico measurements showed absolute differences between the first and second measurements that exceeded 10%.
  
  
  CONCLUSIONS
  The inter-observer variability for CT measurement of the glenoid surface using the CT Pico method was high when compared with laser, in the assessment of glenoid surface in cadaveric specimens, thus the CT Pico method is not reliable and could cause errors in the clinical management of the patient. Level of evidence Level II, Development of diagnostic criteria on consecutive patients (with universally applied reference "gold" standard).
authors.affiliation: Department of Radiology, University of Parma, Parma Hospital, Via Gramsci, 14-43126, Parma, Italy, massimo.defilippo@unipr.it.
authors.forename: Massimo
authors.initials: M
authors.lastname: De Filippo
authors.forename: Luca
authors.initials: L
authors.lastname: Saba
authors.forename: Giulio
authors.initials: G
authors.lastname: Negrini
authors.forename: Mario
authors.initials: M
authors.lastname: Silva
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Pedrazzi
authors.forename: Francesco
authors.initials: F
authors.lastname: Pogliacomi
authors.forename: Alessandro
authors.initials: A
authors.lastname: Castagna
mesh_terms: D002102:Cadaver; D061165:Glenoid Cavity / Q000000981:diagnostic imaging*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional; D007593:Joint Instability / Q000000981:diagnostic imaging; D007834:Lasers; D015588:Observer Variation; D015203:Reproducibility of Results; D012540:Scapula / Q000000981:diagnostic imaging; D012785:Shoulder Joint / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed / Q000379:methods*