A retrospective study on findings of canine hip dysplasia screening in Kenya

Radiographic quantification of the normal and near-normal coxofemoral conformation in Labrador Retrievers and German Shepherds: a comparative study

BACKGROUND

Canine hip dysplasia (CHD) is a multifactorial disease affecting large breed dogs with associated joint laxity and incongruity that predisposes them to osteoarthritis. The purpose of the study is to objectively compare the conformation of normal and near-normal coxofemoral joints (CFJS) in Labrador Retrievers versus German Shepherds on the extended ventrodorsal radiograph. Investigated groups were categorized as normal and near-normal CFJS according to the morphometric criteria established by the FCI scoring system. Center-edge (CE) angle, Norberg angle (NA), indices of dorsal AFH coverage width and area, acetabular slope (AS) angle, and inclination angle were determined for each group. CE angle and AS angle were modified from previously described human techniques. The width and area of dorsal AFH coverage were standardized by the corresponding femoral head diameter and area. Variables were compared between groups using an unpaired, two-tailed t-test. A Spearman correlation coefficient determined the relationship between selected variables.

RESULTS

In Labradors, CE angle (lateral coverage) and dorsal AFH coverage area index (dorsal coverage) were greater in normal versus near-normal CFJS. In German Shepherds, lateral AFH coverage (CE angle and NA) was greater in normal versus near-normal hip joints; whereas, dorsal AFH coverage did not differ between the two groups. Lateral AFH coverage was greater in normal versus near-normal CFJS of both breeds. In Labradors, the inclination angle was greater in near-normal versus normal CFJS. Normal CFJS of Labradors revealed greater lateral and dorsal AFH coverages compared to German Shepherds. Near-normal joints of Labradors showed greater lateral AFH coverage compared to those of German Shepherds; whereas, dorsal AFH coverage did not differ between the two breeds. A steeper acetabular slope angle was noted in normal and near-normal CFJS of German Shepherds compared to Labrador Retrievers. The inclination angle of near-normal joints was greater in Labrador Retrievers compared to German Shepherds.

CONCLUSIONS

Overall, normal and near-normal CFJS of German Shepherds had lesser AFH coverage and steeper acetabular slope angle compared to Labrador Retrievers. Labrador Retrievers and German Shepherds with CE-angles < 27° and < 21.8°, dorsal AFH coverage width indices < 51 and < 49%, and/or dorsal AFH coverage area indices < 53 and < 50%, respectively, may be consistent with CHD. Thus, the authors would recommend excluding subjects with lower values from breeding. Validating the reported measurements is still warranted.

Modified FCI (Fédération Cynologique Internationale) Scoring of the Coxofemoral Joint in Labrador Retrievers Without and With Hip Dysplasia

The objective is to propose a modified FCI scoring protocol of the canine hip joint via: (1) providing morphometric criteria of each score; (2) quantifying the extent of lateral and dorsal acetabular femoral head (AFH) coverage; (3) evaluating the steepness of cranial acetabular edge (acetabular index angle) and inclination angle (IA) in normal and dysplastic coxofemoral joints of Labrador Retrievers. The long-term goal is to achieve a selective breeding protocol using parental phenotypically healthy coxofemoral joints based on the standard extended-leg VD radiograph to help reduce the prevalence of CHD among offspring. Investigated populations were classified into normal (grade A) and dysplastic coxofemoral joints (grades B to E) based on the morphometric criteria previously established by the conventional FCI scoring system. Center-edge (CE) angle, Norberg angle (NA), indices of dorsal AFH coverage width and area, acetabular index angle, and inclination angle were determined for each group. Variables were compared between groups using ANOVA. Spearman correlation coefficient was used to determine the linear relationship between selected variables. Overall, all radiographic measurements differed significantly (P < 0.0001) among the five tested groups using ANOVA test. Dorsal AFH coverage area index was the only measure that differed significantly (P ≤ 0.007) between every two consecutive groups using Tukey's test. Significant correlations were identified between the Norberg and CE angles (r s = 0.95, P < 0.0001), the width and area of dorsal AFH coverage (r s = 0.96, P < 0.0001), and the radiographic techniques utilized to assess lateral vs. dorsal AFH coverage (r s ≥ 0.80, P < 0.0001). Evaluation of CE-angle, dorsal AFH coverage area index and acetabular index angle is recommended during selective breeding to include parents with radiographically healthy joints and reduce the incidence of hip dysplasia among offspring. Dogs with CE-angle <27°, dorsal AFH coverage area index <53%, and/or acetabular index angle >9° may be consistent with hip dysplasia and are recommended to be excluded from potential breeding groups. Re-evaluation of coxofemoral joints with borderline values located between near-normal and mildly dysplastic coxofemoral joints is strongly recommended to be performed after 6 months.

Selection of Breeding Stock among Australian Purebred Dog Breeders, with Particular Emphasis on the Dam

Every year, thousands of purebred domestic dogs are bred by registered dog breeders. Yet, little is known about the rearing environment of these dogs, or the attitudes and priorities surrounding breeding practices of these dog breeders. The objective of this study was to explore some of the factors that dog breeders consider important for stock selection, with a particular emphasis on issues relating to the dam. Two-hundred and seventy-four Australian purebred dog breeders, covering 91 breeds across all Australian National Kennel Club breed groups, completed an online survey relating to breeding practices. Most breeders surveyed (76%) reported specialising in one breed of dog, the median number of dogs and bitches per breeder was two and three respectively, and most breeders bred two litters or less a year. We identified four components, relating to the dam, that were considered important to breeders. These were defined as Maternal Care, Offspring Potential, Dam Temperament, and Dam Genetics and Health. Overall, differences were observed in attitudes and beliefs across these components, showing that there is variation according to breed/breed groups. In particular, the importance of Maternal Care varied according to dog breed group. Breeders of brachycephalic breeds tended to differ the most in relation to Offspring Potential and Dam Genetics and Health. The number of breeding dogs/bitches influenced breeding priority, especially in relation to Dam Temperament, however no effect was found relating to the number of puppies bred each year. Only 24% of breeders used their own sire for breeding. The finding that some breeders did not test for diseases relevant to their breed, such as hip dysplasia in Labrador Retrievers and German Shepherds, provides important information on the need to educate some breeders, and also buyers of purebred puppies, that screening for significant diseases should occur. Further research into the selection of breeding dams and sires will inform future strategies to improve the health and behaviour of our best friend.