title: Quantification of humeroulnar incongruity in labrador retrievers with and without medial coronoid disease.
abstract: OBJECTIVE
  To quantify humeroulnar incongruity on elbow radiographs in Labrador Retrievers with or without medial coronoid disease (MCD).
  
  
  METHODS
  Retrospective study of 92 elbows.
  
  
  METHODS
  Radiographic projections of elbow joints from Labrador Retrievers with MCD (n = 42 elbows; 26 dogs) and without MCD (n = 50 elbows; 25 dogs).
  
  
  METHODS
  The congruity of the humeroulnar joint was measured using an index of subluxation (SI) for each elbow. SI was defined as the distance between the centers of 2 circles drawn along the margins of the incisura trochlearis and the trochlea of humerus on mediolateral digital radiographic projections, normalized by the radius of the circle circumscribing the humeral trochlea. SI was compared between right and left elbows with and without pathology using a Wilcoxon test for paired data, and between normal and abnormal groups with a Wilcoxon test for unpaired data. Mismatch between ulnar curvature and curvature of humeral trochlea and radioulnar incongruency were also noted (Wilcoxon test). The intraobserver repeatability, correlation between SI and radioulnar incongruency, and between SI and mismatch elbow curvature were estimated with a Pearson's correlation coefficient.
  
  
  RESULTS
  Intraobserver repeatability of SI measurement was high (r = 0.97). Mean ± SD humeroulnar incongruity (SI) was greater in elbows with MCD (18.5 ± 6.6) than in the normal elbows (1.7 ± 2.0, P < 0.001). The difference between the diameters of the curvatures of the ulnar and humeral trochlea was greater in elbows with MCD (12.5 ± 4.4) than in the normal group (10.7 ± 4.1, P < 0.05). A moderate correlation was found between the degree of humeroulnar incongruity and a radioulnar step (r = 0.63); however, no correlation was identified between SI and the difference between the diameters of the curvatures of the ulnar and humeral trochleae (r = 0.14).
  
  
  CONCLUSIONS
  We propose a radiographic index to measure humeroulnar incongruity on mediolateral digital radiographic projections. This index (SI) supports the presence of humeroulnar incongruity in Labrador Retrievers with MCD. Further evaluation of its reproducibility and clinical importance are warranted. Although there is a moderate correlation between humeroulnar incongruity and radioulnar incongruency, causation has not been established.
authors.affiliation: Faculty of Veterinary Medicine, Small Animal Clinic, University of Veterinary and Pharmaceutical Sciences Brno, Brno, Czech Republic. proksp@vfu.cz
authors.forename: Pavel
authors.initials: P
authors.lastname: Proks
authors.forename: Alois
authors.initials: A
authors.lastname: Necas
authors.forename: Ladislav
authors.initials: L
authors.lastname: Stehlik
authors.forename: Robert
authors.initials: R
authors.lastname: Srnec
authors.forename: Dominique J
authors.initials: DJ
authors.lastname: Griffon
mesh_terms: D000818:Animals; D016022:Case-Control Studies; D004283:Dog Diseases / Q000000981:diagnostic imaging* / Q000473:pathology; D004285:Dogs; D005260:Female; D005552:Forelimb / Q000000981:diagnostic imaging* / Q000473:pathology; D006811:Humerus / Q000000981:diagnostic imaging* / Q000473:pathology; D007592:Joint Diseases / Q000000981:diagnostic imaging / Q000473:pathology / Q000662:veterinary*; D008297:Male; D015588:Observer Variation; D011859:Radiography; D012189:Retrospective Studies; D014457:Ulna / Q000000981:diagnostic imaging* / Q000473:pathology