Hip dysplasia in dogs

Inspired by the desire to find an objective selection criterion which might be useful notably in borderline cases of hip dysplasia, 1265 sets of radiographs, taken on 1128 pedigree Rottweilers, have been assessed for 12 particulars of the joints; three subevaluations as well as a final score (FS) have been obtained for each individual involved. The data so obtained from a representative subpopulation have been analysed for their contributions to the 12 assessments leading towards the value of the final score. This article shows that FS, most notably in the borderline cases, is due to a subjective assessment, which disqualifies FS as a selection criterion. In pursuit of this line of thought, it was considered desirable to investigate whether FS could be replaced by some measurable (hence objective) particular assessment, such as the Norberg-Olsson Value (N). In conclusion, we find that N on its own, though objective, fails to meet the requirements.

Diagnosis of canine hip dysplasia and selection against this trait

N, the Norberg-Olsson value, when regarded as the single predictor of FS in the total research subpopulation, leads to an unacceptably high proportion of misclassifications. These misclassifications are found to be much reduced in number on elimination of all animals suffering from bone deformities (BD) as perceivable on the radiographs. Discriminant analysis, applied to the findings in 915 Rottweilers, yields the combination of a suitable high N with the absence of perceivable bone deformities as a more acceptable predictor for FS, specially applicable in borderline cases.

Hip dysplasia and dog breeding

Hip dysplasia is considered to be one of the most serious problems in dog breeding. In the past 20 years the studies of, and the attempts to control, this condition have been directed mainly to the overall picture of the abnormality of the hips. The various efforts have resulted in a decrease in the incidence of HD in several breeds of dogs. For other breeds the results have not been very convincing, however. In some instances they are even said to be conflicting with other aims of breeding. Based on these data some separate studies have recently been performed in respect of the details of the disorders in the hip joints and of the heritability of these elements. The present study concerns itself with the roots of the disorders as they are observed in the various breeds. A great variety of data indicates that selection within the canine species for specific morphological traits must be considered as one of the most important roots of the occurrence of HD. The collected data strongly indicate that improvements in the HD status in the various breeds can be reached by selection against specific disorders of the hip joints in these breeds.