Authors:Mário Ginja, António Silvestre, António Ferreira, José Gonzalo-Orden, Maria Orden, Pedro Melo-Pinto, Maria Llorens-Pena and Jorge Colaço
Two hundred and fifteen Estrela Mountain Dogs (EMD) were examined using the PennHIP method between 2002 and 2006. Passive hip laxity (PHL) was estimated calculating the distraction index (DI). Pedigree information was obtained from the Portuguese Kennel Club. The heritability and breeding values were estimated using the linear Animal Model. The DI, using as reference the worst joint of each animal, ranged from 0.15 to 1.12 (0.55 ± 0.19). The PHL was equal in right and left sides, and was higher in females than in males (P > 0.05 and P < 0.01 in the
-test, respectively). The estimated heritability was 0.83 ± 0.11. The mean breeding values for PHL were stable in EMD born between 1991 and 2003, and showed an improvement in 2004 and 2005. The data confirm high PHL in breeds with high prevalence and severity of canine hip dysplasia. The high heritability indicates that the DI could be reduced in the breed if PHL were used as a selection criterion. The early favourable evolution of DI breeding values could be related with the increase of voluntary radiographic hip screening in the last years, and the subsequent introduction of hip quality as a breeding criterion.
Authors:M. M. D. Ginja, A. J. A. Ferreira, M. Silvestre, J. M. Gonzalo-Orden and M. P. Llorens-Pena
Repeatability and reproducibility of Distraction Index (DI) measurements in the PennHIP method were evaluated in 100 dogs. The PennHIP distraction views sent to the PennHIP Analysis Center (PAC) were duplicated, digitalised, and identified with a code, and an adequate computer software was used for DI measurements. One examiner performed two DI measurement sessions, evaluating individually 200 hip joints. The scoring repeatability and reproducibility were estimated calculating the Intraclass Correlation Coefficient (ICC) between the two DI measurement sessions and between the second DI measurement session and the DI in PAC reports, respectively. The ICC for repeatability was 0.97 [95% confidence interval (CI), 0.96 to 0.98], and the ICC for reproducibility was 0.95 (95% CI, 0.93 to 0.96). The results suggest that the DI measurement method described is repeatable and can reproduce the PAC reports with confidence. Distraction indices measured in different PennHIP studies, using this DI measurement method and performed by trained researchers, can be considered interchangeable.