Canine hip dyslasia: the significance of the Norberg angle for healthy breeding.

Abstract

OBJECTIVES: To assess the reproducibility of the F&#xe9;d&#xe9;ration Cynologique Internationale (FCI) classification over time, and between assessors and to evaluate the benefit of computer-assisted measurement of the Norberg angle and of its percentile ranking by breed for the diagnosis of canine hip dysplasia, and for the selection of couples for breeding. METHODS: During the time period of 2006 to 2010, 5094 hip radiographs were evaluated according to the FCI rules, and 4400 have been submitted for statistical analysis. A system of computer-assisted image analysis (Digimizer(&#xae;) , MedCalc Software Ltd, Mariakerke, Belgium) was used to measure the Norberg angle. The Norberg angle value of individual dogs was expressed as percentile rank by breed. RESULTS: The agreement between individual assessors was highly significant (P<0&#xb7;001), but there were important variations over time of the ratio of classes A or B. The Norberg angle and the percentile rank accurately discriminated between dogs with or without canine hip dysplasia, with positive and negative likelihood ratios of 6&#xb7;31 and 0&#xb7;21, respectively, for the Norberg angle at criterion value of 102&#xb7;2&#xb0;, and 4&#xb7;21 and 0&#xb7;18 for the percentile rank at criterion value of the 25th percentile. CLINICAL SIGNIFICANCE: The percentile rank of the Norberg angle may be a valuable tool for breeding selection.