title: Sensitivity and specificity of 3D models of the radioulnar joint cup in combination with a sphere fitted to the ulnar trochlear notch for estimation of radioulnar incongruence in vitro.
abstract: OBJECTIVE
  To determine the sensitivity and specificity of estimation of radioulnar incongruence (RUI) by use of 3-dimensional (3D) image renderings in combination with a sphere fitted to the ulnar trochlear notch.
  
  
  METHODS
  In vitro study.
  
  
  METHODS
  Right forelimbs (n = 8) of canine cadavers weighing >20 kg.
  
  
  METHODS
  CT-based 3D models (n = 63) of the radioulnar joint cup with different states of RUI were used. A sphere was fitted to the trochlear notch of each of the models and 2 independent observers estimated RUI based on the relation of the sphere and the radial joint surface blinded to the true state of RUI at 1 mm precisely (-2 mm to +2 mm).
  
  
  RESULTS
  Mean sensitivity and specificity for detecting any form of incongruent joint was 0.94 and 0.89, respectively. Evaluating a positive step (short radius) versus a congruent joint resulted in a mean sensitivity and specificity of 0.89 and 0.96, respectively. A negative RUI (short ulna) was diagnosed with a mean sensitivity and specificity of 1.00 and 0.92, respectively. Intra-class-correlation coefficient for inter-observer agreement was 0.99.
  
  
  CONCLUSIONS
  Fitting a sphere to the ulnar trochlea notch significantly improves diagnostic accuracy of 3D models of the radioulnar joint cup when diagnosing RUI.
authors.affiliation: Department of Small Animal Medicine, University of Leipzig, Leipzig, Germany.
authors.forename: Hamdi
authors.initials: H
authors.lastname: Eljack
authors.forename: Hinnerk
authors.initials: H
authors.lastname: Werner
authors.forename: Peter
authors.initials: P
authors.lastname: Böttcher
mesh_terms: D000818:Animals; D002102:Cadaver; D003198:Computer Simulation; D004285:Dogs / Q000033:anatomy & histology*; D015588:Observer Variation; D012680:Sensitivity and Specificity; D012785:Shoulder Joint / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed