Lumbosacral transitional vertebra in 14 dog breeds in Norway: Occurrence, risk factors and association with hip dysplasia

A lumbosacral transitional vertebra (LTV) is a congenital anomaly of the spine and has been suggested to predispose to canine hip dysplasia (CHD). This retrospective, cross-sectional study investigated the prevalence of LTV and CHD among 14 dog breeds in Norway, the possible associations with risk factors, and whether LTV was a risk factor for the development of hip dysplasia. The results were based on evaluation of ventrodorsal radiographs from the CHD screening program from the Norwegian Kennel Club from February 2014 to January 2022. A total of 13,950 dogs were included in the study. For statistical analysis, CHD grades were reclassified from the official Federation Cynologique Internationale (FCI) grades into three grades: CHD free (CHD=A, B), CHD mild (CHD=C), and CHD severe (CHD=D, E). In the study sample, the overall occurrence of LTV was 18.5%, of which 32.9% were type 1, 45.7% type 2% and 21.4% type 3. The occurrence of LTV varied significantly among the included breeds, ranging from 9.5% to 46.2%. There was no association between sex and LTV. The frequencies of CHD grades were A: 43.1%; B: 31.4%; C: 18.4%; D: 6.0%; E: 1.1%. There was a statistically significant association with mild and severe CHD in dogs with LTV type 2 and LTV type 3 (P< 0.001). In the population studied, the prevalence of LTV was different among breeds. This supports initial data on the heredity of LTV and the diverse occurrence of LTV among breeds. Our results indicate that LTV type 2 and type 3 are associated with mild and severe CHD development. Therefore, this study has potentially identified an additional risk factor for the development of hip dysplasia.

Prevalence of canine hip dysplasia in 10 breeds in France, a retrospective study of the 1997-2017 radiographic screening period

Canine hip dysplasia (HD) is a complex developmental disease of the coxo-femoral joint and is one of the most common orthopedic conditions in dogs. Due to the genetic contribution, most of the programs fighting against HD recommend selective breeding that excludes affected dogs. Using the best-scoring dogs for breeding may reduce the prevalence of HD. In France, the phenotypic screening of coxo-femoral joint conformation remains a strategy for breeders to establish selection decisions. The HD prevalence was evaluated in 10 breeds, based on the assessment of 27,710 dogs, during the 1997-2017 screening period, which was divided into 3 homogeneous cohorts for analysis. The global HD prevalence varied widely among breeds from 5% (Siberian Husky) to 51.9% (Cane Corso). It decreased over time in 6 breeds, among which 4 (Cane Corso, Gordon Setter, Rottweiler and White Swiss Shepherd) showed a significant decrease. A statistically significant increase in HD prevalence was noted for the Siberian Husky. Although the efficacy of phenotype-based breeding programs remains controversial, our results are in accordance with several recent studies showing that long-term selection policies are valuable, as they may help decreasing the HD prevalence in some breeds. The complementary use of more recent tools such as estimated breeding values and genomics would probably help breeders achieve more substantive results.

Etiopathogenesis of Canine Hip Dysplasia, Prevalence, and Genetics

First identified in 1935, canine hip dysplasia is thought to be the most common orthopedic condition diagnosed in the dog. It is most prevalent in large and giant breed dogs, with a complex polygenic mode of inheritance, and relatively low heritability. External factors including caloric intake when growing have a significant effect on phenotypic expression. Initial joint laxity progresses to osteoarthritis due to subluxation and abnormal wearing. Selective breeding programs to attempt to decrease prevalence have shown modest results so far.

Monitoring Hip and Elbow Dysplasia achieved modest genetic improvement of 74 dog breeds over 40 years in USA

Hip (HD) and Elbow Dysplasia (ED) are two common complex developmental disorders of dogs. In order to decrease their prevalence and severity, the Orthopedic Foundation for Animals (OFA) has a voluntary registry of canine hip and elbow conformation certified by boarded radiologists. However, the voluntarily reports have been severely biased against exposing dogs with problems, especially at beginning period. Fluctuated by additional influential factors such as age, the published raw scores barely showed trends of improvement. In this study, we used multiple-trait mixed model to simultaneously adjust these factors and incorporate pedigree to derive Estimated Breeding Values (EBV). A total of 1,264,422 dogs from 74 breeds were evaluated for EBVs from 760,455 hip scores and 135,409 elbow scores. These EBVs have substantially recovered the reporting bias and the other influences. Clear and steady trends of genetic improvement were observed over the 40 years since 1970. The total genetic improvements were 16.4% and 1.1% of the phenotypic standard deviation for HD and ED, respectively. The incidences of dysplasia were 0.83% and 2.08%, and the heritabilities were estimated as 0.22 and 0.17 for hip and elbow scores, respectively. The genetic correlation between them was 0.12. We conclude that EBV is more effective than reporting raw phenotype. The weak genetic correlation suggested that selection based on hip scores would also slightly improve elbow scores but it is necessary to allocate effort toward improvement of elbow scores alone.

[Multivariate prediction of breeding values for canine hip and elbow dysplasia as well as humeral osteochondrosis in the Bernese mountain dog]

The aim of this study was the multivariate prediction of breeding values for canine hip dysplasia (CHD), elbow dysplasia (ED) and humeral osteochondrosis (OCD) for Bernese mountain dogs of the Schweizer Sennenhund-Verein für Deutschland e. V. (SSV). For the analysis the pedigrees of eight generations and radiographic screening results of the birth cohorts from 1995-2008 were used. The number of dogs with scores for CHD was 5513, for ED 5175 and OCD 1240. Breeding values were multivariately predicted using a mixed linear model for CHD, ED and OCD as well as for the occurrence of a fragmented coronoid process of the medial ulna (FCP) and the ED-score without FCP. The pedigree breeding value (eRZWp) which is used as the selection criterion reached a reliability to predict the phenotype of the offspring at 2.8-2.9% for CHD, 2.9% for ED, 1.1% for ED without FCP, 1.8% for FCP and 0.8-1.3% for OCD. The reason for the low predictive value of the eRZW(P) is caused by the very high influence of the own performance of the animal and the very uniform distribution of contributions of the breeding values of the relatives.These results indicate that even a multivariate prediction of breeding values does not lead to a faster progress in breeding against CHD and ED, however, does allow breeding against OCD in the Bernese mountain dog. In comparison to phenotypic selection, there is some improvement in the selection response when using breeding values. Due to the general low predictive power of breeding values better approaches for selection of future breeding animals are urgently warranted to achieve improvements in breeding Bernese mountain dogs.

[Multivariate genetic analysis of canine hip and elbow dysplasia as well as humeral osteochondrosis in the Bernese mountain dog]

In the present study genetic parameters for canine hip dysplasia (CHD), canine elbow dysplasia (CED) and osteochondrosis dissecans of the humeral head (OCD) were analysed in Bernese mountain dogs. The data set included the official scores for CHD and CED from 5534 Bernese mountain dogs born in the years 1995-2008. A multivariate linear animal model was employed to estimate heritabilities, additive genetic and residual correlations using residual maximum likelihood (REML). Heritability estimates were h2 = 0.26 for CHD, h2 = 0.22 for CED and h2 = 0.40 for OCD. The additive genetic correlation between CHD and CED was 0.31, between CHD and OCD 0.25, and between CED und OCD -0.49. A further multivariate analysis of the prevalence of the FCP (fragmented coronoid processus), CHD and OCD revealed a heritability of h2 = 0.59 for FCP. The additive genetic correlations among FCP and CHD as well CED except FCP were positive, but negative with OCD. Multivariately estimated breeding values will lead to higher genetic progress because the correlation structure of the traits can be taken into account and possible genetic antagonisms among traits are better reflected in the breeding values.

Genetic and phenotypic trends in canine hip dysplasia in the German population of German shepherd dogs

Phenotypic and genetic trends were examined in 157,455 German shepherd dogs of the German population born between 1985 and 2003 which were Xrayed for canine hip dysplasia (CHD). A subset of 40,270 dogs born between 1998 and 2003 was examined for which information was available on age at examination and X-raying veterinary practitioner. Relative breeding values were predicted using best linear unbiased prediction methods (BLUP) and Gibbs Sampling. There was an almost linear and significant decline in both phenotypic and genetic trends for CHD scores (scale 1 to 5 for CHD free to severe CHD) over a period of 19 years, with b = -0.021 +/- 0.002, and b = -1.69 +/- 0.05, respectively. After introduction in 1999 of a selection scheme based on relative breeding values (RBVs, mean 100, standard deviation 20) of a linear animal model, phenotypic and genetic trends declined less than before 1999, with b = -0.019 +/- 0.011 and b = -1.43 +/- 0.29. Analysis of the effects of RBVs of parental combinations among sires and dams on the percentage of non-affected progeny showed that lower RBVs were associated with a higher percentage of non-affected progeny than were higher RBVs. In addition, it was also shown that selection procedures based on RBVs are more efficient than selection schemes based on phenotypic records of parents. When the maternal RBV was above 100, the proportion of non-affected progeny was between 10% and 20% lower than when the maternal RBV was below or equal to 100. There was a significant relationship between higher inbreeding coefficients and higher RBVs of the animal.

Canine hip dysplasia of selected breeds--results obtained by two Polish clinics based on radiological examination conducted in 1997-2006

Canine Hip Dysplasia (CHD) is still a significant health problem among dogs of so called predisposed breeds where this disease is revealed even among 30% individuals of the whole population. The present results were obtained by two clinics and deal with CHD occurrence among the most frequently and predisposed breeds in Olsztyn and Siemianowice Slaskie/Upper Silesia, Poland. Radiographs of hip joints were described using Riser's method. Altogether 2279 dog were examined including 2113 animals which were analysed. The German Shepherd Dog was the prevalent breed found in both clinics, but CHD was not common in this breed. In the Olsztyn Clinic, the most numerous group affected by CHD was Neapolitan Mastiff (60%), while in the Siemianowice Slaskie Clinic, dysplasia dominated in Bernese Mountain Dog (46%).

Retrospective evaluation of the long-term outcome of non-surgical management of 74 dogs with clinical hip dysplasia

The long-term outcome for dogs treated non-surgically for clinical signs of canine hip dysplasia were evaluated retrospectively; 74 dogs were evaluated by a postal questionnaire sent to their owners, and 24 of these were also evaluated by a veterinary clinical examination. A total of 11 outcome variables were evaluated. Depending on the variable assessed, between 31 (41.9 per cent) and 49 (66.2 per cent) of the dogs remained clinically affected according to their owner's assessment, and between 17 (70.8 per cent) and 23 (95.8 per cent) of the 24 dogs had abnormalities attributed to hip osteoarthritis according to the veterinary assessment. Orthopaedic abnormalities other than hip dysplasia affected 17 of the 24 dogs. Long-term medications had been prescribed for the treatment of clinical signs associated with hip dysplasia in 41 of the 74 dogs.

Clinical and genetic assessments of hip joint laxity in the Boykin spaniel

Canine hip dysplasia (CHD) is characterized by a malformation of the hip joint that leads to joint laxity and consequential degenerative joint disease. The most widely used method for diagnosis of CHD is the ventrodorsal hip-extended radiologic view, commonly referred to as the Orthopedic Foundation for Animals (OFA) method. The method of the University of Pennsylvania Hip Improvement Program (PennHIP), an alternative technique that is based on hip joint laxity, provides a quantitative assessment, the distraction index (DI), of the likelihood of the development of CHD because of increased laxity in the hip joint. Linear regression analysis showed that, across many breeds of dog, the incidence of CHD, as defined by the OFA, is positively correlated with the mean DI, the determination coefficient (r2) being 26%. We used families of Boykin spaniels (BSs) to determine the level of joint laxity in the breed and to conduct an initial whole-genome screening to identify markers that co-segregate with increased joint laxity. Although there was a positive correlation between the incidence of hip dysplasia and increased joint laxity, we did not find significant linkage in the 28 BSs that underwent genotyping, likely owing to the small size of the pedigree.

LUMBOSACRAL TRANSITIONAL VERTEBRAE IN DOGS: CLASSIFICATION, PREVALENCE, AND ASSOCIATION WITH SACROILIAC MORPHOLOGY

The prevalence of lumbosacral transitional vertebrae (LTV) was determined by reviewing the pelvic radiographs of 4000 medium- and large-breed dogs of 144 breeds routinely screened for canine hip dysplasia. An LTV was seen in 138 (3.5%) dogs. The prevalence was higher in German Shepherd dogs and Greater Swiss Mountain dogs than in the other breeds, suggesting a genetic predisposition. There was no gender predisposition. The transverse processes of the LTV were divided into three types based on their morphological characteristics: lumbar type or type 1; intermediate type or type 2; and sacral type or type 3. In a symmetric LTV, both transverse processes are of the same type, while in an asymmetric LTV they are not. The frequency of occurrence of symmetric and asymmetric LTV was similar. In symmetric LTV, intermediate-type transverse processes predominated. Most of the asymmetric LTV had an intermediate-type transverse process combined with a lumbar or sacral type, respectively. Highly asymmetric LTV were often angled relative to the adjacent vertebrae. We hypothesize that an LTV is not the result of transformation of a lumbar into a sacral vertebra or vice versa, but rather is an autonomous intermediate type of vertebra. It occurs when the point of contact of the pelvis with the vertebral column is slightly cranial or caudal to its normal position. The resulting formative stimulus on the vertebral ossification centers, sagittally still separated, causes the various morphologies seen in LTV including the asymmetric variations.

Prevalence of cranial cruciate ligament rupture in a population of dogs with lameness previously attributed to hip dysplasia: 369 cases (1994-2003)

OBJECTIVE

To determine the prevalence of cranial cruciate ligament rupture (CCLR) in dogs with lameness previously attributed to canine hip dysplasia (CHD).

DESIGN

Retrospective study.

ANIMALS

369 client-owned dogs.

PROCEDURES

Hospital medical records from 1994 to 2003 were reviewed for dogs in which the referring veterinarian had diagnosed hip dysplasia or hip pain. Dogs were designated as having hind limb lameness because of partial or complete CCLR or CHD.

RESULTS

8% of dogs were sexually intact females, 43% were spayed females, 14% were sexually intact males, and 35% were castrated males. Mean age was 3.8 years (range, 3 months to 15 years). The most common breeds were the Labrador Retriever (21%), German Shepherd Dog (13%), and Golden Retriever (11%). The prevalence of CCLR as the cause of hind limb lameness was 32% (95% confidence interval, 27.2% to 36.8%). The distribution of CCLR among hind limbs was left (29%), right (28%), and bilateral (43%). Of 119 dogs with CCLR, 94% had concurrent radiographic signs of CHD, 92% had stifle joint effusion, and 81% had a cranial drawer sign.

CONCLUSIONS AND CLINICAL RELEVANCE

On the basis of the high prevalence of CCLR in dogs referred for lameness because of CHD, it is important to exclude other sources of stifle joint disease before making recommendations for treatment of CHD.

A radiological study of the incidence of unilateral canine hip dysplasia

The authors reviewed pelvic radiographs of 891 dogs in a retrospective study, to determine the incidence of Unilateral Canine Hip Dysplasia (UCHD). Results show that 149 (16.7%) dogs had UCHD. Comparing dogs affected uni- and bilaterally, results show a maximum of 37.6% with UCHD in dogs less than 12 month old, 22.8% in dogs between 12-24 months of age, 25.5% in dogs between 25-72 months and 14.1% in dogs older than 73 months.

Estimates of prevalence of hip dysplasia in Golden Retrievers and Rottweilers and the influence of bias on published prevalence figures

OBJECTIVE

To estimate prevalence of canine hip dysplasia (CHD) in Golden Retrievers and Rottweilers and identify sources of bias in published reports.

DESIGN

Prospective study.

ANIMALS

200 clinically normal Golden Retrievers and 140 clinically normal Rottweilers between 24 and 60 months of age referred for hip evaluation (group 1) and 93 clinically normal dogs evaluated for Orthopedic Foundation for Animals (OFA) hip certification (group 2).

PROCEDURE

Hip-extended pelvic radiographs from group 1 dogs were screened for CHD. Radiographs were evaluated twice; the first interpretation used an OFA-type subjective 7-point scoring system, and the second included the caudolateral curvilinear osteophyte as an additional sign of degenerative joint disease. The OFA submission rate of group 2 dogs was determined from the number of official reports returned from the OFA.

RESULTS

Prevalence of CHD in Golden Retrievers ranged from 53% to 73% and in Rottweilers ranged from 41% to 69%. Among dogs referred for OFA evaluation, radiographs from 49 (53%) were submitted to OFA. Of submitted radiographs, 45 (92%) were normal; of radiographs not submitted, 22 (50%) were normal. Radiographs with normal-appearing hips were 8.2 times as likely to be submitted to the OFA. Compared with Golden Retrievers, Rottweiler radiographs were significantly more likely to be submitted for OFA certification.

CONCLUSIONS AND CLINICAL RELEVANCE

Prevalence of CHD in these 2 breeds may be much higher than previously reported in the United States. Results suggest substantial bias in the OFA database, which causes lower estimates of prevalence of CHD.

Incidence, risk factors, and heritability estimates of hind limb lameness caused by hip dysplasia in a birth cohort of Boxers

OBJECTIVE

To determine incidence, risk factors, and heritability estimates of hind limb lameness caused by hip dysplasia in a birth cohort of Boxers.

ANIMALS

1733 Boxers from 325 litters.

PROCEDURE

Status of Boxers with respect to clinical signs of canine hip dysplasia (cCHD) was registered during an 8-year period. Survival analysis accounted for dogs lost to follow-up. Effective heritability for developing cCHD was estimated by use of a proportional hazard model on the basis of the Weibull distribution. Parametric survival models were developed to identify the influence of potential risk factors.

RESULTS

Cumulative hazard rate for cCHD from 7 weeks to 8 years of age was 8.5%. Dogs that were kept on a floor covered with a slippery material were 1.6 times as likely to develop cCHD, compared with dogs kept on a nonslippery floor. Risk of cCHD doubled in dogs from litters with a high preweaning mortality rate. Dogs that were neutered at 6 months prior to a diagnosis of CHD were 1.5 times as likely to develop cCHD, compared with sexually intact dogs. Dogs >5 years of age were 1.8 times as likely to develop cCHD, compared with younger dogs. Estimated effective heritability of cCHD was 0.11. In terms of the risk of cCHD in progeny, mean estimated breeding value (EBV) of the 10 best and 10 worst sires was -0.32 and 0.42, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Registration of Boxers that develop cCHD may provide a strategy for disease prevention. In addition to diagnostic evaluation of radiographs, sire EBVs provide useful information for breeding selection decisions.

Use of the caudolateral curvilinear osteophyte as an early marker for future development of osteoarthritis associated with hip dysplasia in dogs

OBJECTIVE

To determine the relationship between the caudolateral curvilinear osteophyte (CCO) and osteoarthritis associated with hip dysplasia in dogs.

DESIGN

Longitudinal cohort study.

ANIMALS

48 Labrador Retrievers from 7 litters.

PROCEDURE

In each of 24 sex- and size-matched pairs fed the same diet, a restricted-fed dog was fed 25% less than a control dog for life. The dogs' hips were evaluated in the standard ventrodorsal hip-extended radiographic projection at 16, 30, and 52 weeks of age and then yearly for life. Histologic examination of hip joint tissues was performed on 45 dogs.

RESULTS

Median age at death was 11.2 years. Adjusting for feeding group, dogs with a CCO were 3.7 times as likely to develop radiographic signs of osteoarthritis than those without a CCO. Stratified by diet, 100% of the control dogs with a CCO developed radiographic signs of osteoarthritis and 55% of restricted-fed dogs with a CCO developed radiographic signs of osteoarthritis. The CCO was the first radiographic change seen in 22 of 29 (76%) dogs with osteoarthritis. Overall, 35 of 37 (95%) dogs with a CCO had histopathologic lesions of osteoarthritis.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicate a relationship between a CCO on the femoral neck and subsequent development of radiographic signs of osteoarthritis in Labrador Retrievers evaluated over their life span. A CCO is an important early radiographic indication of osteoarthritis associated with canine hip dysplasia.

Comparison of three distraction methods and conventional radiography for early diagnosis of canine hip dysplasia

Two radiographic distraction techniques (one employing a wooden lath and, the other, a PennHip distractor), an ultrasonographic distraction method and conventional radiographic Fédération Cynologique Internationale (FCI) hip score were evaluated in eight-month-old Labrador retrievers to determine the most reliable method for predicting radiographic FCI hip score at the age of one year. With reference to the FCI hip score, sensitivity and specificity of the PennHip method were 100 per cent and 54 per cent; sensitivity and specificity of the lath technique were 85 per cent and 71 per cent; whereas they were 62 per cent and 67 per cent for the ultrasonographic method. For all distraction methods, the positive predictive value (PPV) was moderate and the negative predictive value (NPV) was high. Sensitivity, specificity, PPV and NPV were 100 per cent for the FCI hip score. It is concluded that, at the age of eight months, FCI hip score is the most reliable method for predicting FCI hip score at the age of one year in the colony of dogs investigated. Both the PennHip and lath method were also clinically reliable techniques in predicting true negatives. The ultrasonographic distraction method was moderately reliable.

Retrospective analysis of canine miniature total hip prostheses

OBJECTIVE

To determine the practicality and clinical outcome of miniature total hip replacement (THR) in dogs.

STUDY DESIGN

Retrospective study. Sample Population- Seventeen client-owned dogs that had miniature THR.

METHODS

Patient data surveyed included signalment, body weight, diagnosis, implant size, surgical technique, and intraoperative and postoperative complications. Radiographic evaluation included angle of lateral opening of the acetabular component, implant positioning, cement mantle quality, and femoral displacement measurement and ratio. Client questionnaire and orthopedic examination were used to obtain long-term follow-up information.

RESULTS

Miniature THR was performed to address hip dysplasia and secondary osteoarthritis. In 1 dog, a staged bilateral procedure was performed. Mean body weight was 19 kg (range, 12 to 25 kg). Penetration or fissure of the femoral cortex was the most common intraoperative complication and occurred in 3 dogs. In 3 dogs, there was excessive coxofemoral laxity after reduction of the prosthesis. This instability was addressed specifically in 2 dogs by capsulorrhaphy or capsular prosthesis. Postoperative convalescent complications (craniodorsal luxation, 2 dogs; acetabular cup displacement, 1 dog) were related to surgical errors. Aseptic loosening of the femoral implant was diagnosed in 1 dog at 18 months. Mean follow-up time was 17 months (range, 4 to 42 months). Fifteen of 18 (83%) miniature THRs had good or excellent outcomes.

CONCLUSIONS

Miniature THR should be considered a satisfactory alternative to femoral head and neck ostectomy in medium-size dogs affected by hip dysplasia and secondary osteoarthritis. The population of medium-size dogs that might derive more benefit from THR than FHO has yet to be defined.

CLINICAL RELEVANCE

Miniature THR is a viable treatment option in medium-size dogs with hip dysplasia.

Effect of month of birth on hip dysplasia in labrador retrievers and Gordon setters

Recent studies have proposed selective breeding policies for preventing or controlling hip dysplasia, based upon the relationships between the hip scores of the offspring and their parents. However, these studies have ignored the possible effects on an animal's hip score of its age when it was examined and the month in which it was born. This paper describes the results of statistical analyses of large data sets of Kennel Club-registered labrador retrievers and Gordon setters. Regression modelling showed that an animal's hip score depended significantly upon the hip score of its sire and dam, and upon its month of birth. Enlarging the model by including its age when examined made it possible to quantify the significant genetic parental effects and the effects of the animal's month of birth and its age when examined.

Hip dysplasia in labrador retrievers: the effects of age at scoring

Selective breeding policies for preventing or controlling hip dysplasia require accurate estimates of parameters in offspring/parental relationships and estimates of heritability. Recent literature includes some major studies of pedigree breeds of dog, using data derived from the hip dysplasia screening scheme set up by the British Veterinary Association. These publications have not taken into account the age of the animals when they were screened. This study analyses the data from 29,213 labrador retrievers whose ages were known when they screened. The mean hip score of the dogs was positively and significantly correlated with their age. If this relationship with age is ignored, various offspring/parental relationships and the estimates of heritability are likely to be distorted.

Heritability and epidemiology of canine hip-dysplasia score and its components in Labrador retrievers in the United Kingdom

Hip-dysplasia (malformation of the coxofemoral joint) in dogs is a major health problem. Under the British Veterinary Association/Kennel Club's voluntary hip-dysplasia scheme, dog-owners/breeders submit radiographs from animals >1-year-old, to ensure adequate skeletal maturity. An overall hip score quantifies the degree of malformation in the hip joints of these animals, by summing the scores for nine components of the radiographs of both the left and right joints. The hip score data for 29,610 Labrador retrievers (registered with The Kennel Club, UK) were merged with the Kennel Club pedigree database for 472,435 Labrador retrievers. The merged data included the animal's identity, date of birth, sex and hip score and similar records for the dog's relatives, including the hip score if the relative had been tested. In recent years, breeding had been increasingly from tested parents. The mean hip score for male Labradors was significantly higher than that for females. Regression modelling showed a significant, positive dependence of the hip score of the offspring upon the hip scores of its sire, dam and grandparents. Genetic heritability (using data from 13,382 Labrador retrievers comprising 718 litters) was highly significant: 0.34 from the two parents, 0.41 from sire alone and 0.30 from dam alone. Using components data from 2038 offspring Labrador retrievers comprising 1248 litters, three similar estimates of heritability were significant for three major components (Norberg angle, cranial acetabular edge and subluxation); for other components, heritability was significant from the sire but not from the dam. Offspring hip score could be reduced substantially by using only parents with zero hip score.

Breed susceptibility for developmental orthopedic diseases in dogs

A large-scale epidemiological study was conducted to determine breeds at risk for 12 developmental orthopedic diseases (DODs). Developmental orthopedic diseases investigated included canine hip dysplasia (CHD); craniomandibular osteopathy (CMO); fragmented coronoid process; hypertrophic osteodystrophy; Legg-Calvé-Perthes disease; osteochondrosis of the medial humeral condyle, caudal humeral head, femoral condyles, and talar trochlear ridges; panosteitis; patella luxation; and ununited anconeal process. Dogs that were diagnosed with any one of the diseases of interest at any of 10 veterinary teaching hospitals participating in the Veterinary Medical Database from 1986 to 1995 were included as cases. Odds ratios and corresponding 95% confidence intervals were calculated to determine risk. Frequency of diagnosis during the 10-year period ranged from 35 cases (CMO) to 10,637 cases (CHD). The number of breeds at increased risk for a disease ranged from one (CMO) to 35 (CHD). Breed susceptibility for a DOD may suggest a genetic component in the disease etiology. The results of this study serve to increase veterinarians' awareness of breeds susceptible to DODs and may facilitate the control of such diseases by identifying breeds that might benefit from breeding programs or environmental intervention such as dietary modification.

Prevalence of canine hip dysplasia in a veterinary teaching hospital population

The purpose of this study was to determine the prevalence of canine HD in a population in which there was minimal or no prior screening of radiographs for the disorder. Patient information was obtained from the radiographic database at the University of Missouri-Columbia Veterinary Teaching Hospital during the five-year period of 1991-1995. The coxofemoral joints on ventrodorsal radiographs of the pelvis were independently evaluated by three veterinary radiologists. A consensus evaluation of normal, borderline, or dysplastic was compiled. There were 2885 dogs identified representing 116 breeds and the mixbreds. There were 2236 purebred dogs (1071 males and 1165 females) and the prevalence of HD was 19.7%. There were 649 mixbred dogs (340 males and 309 females) and the prevalence of HD was 17.7%. There was no significant difference in the prevalence of HD between sexes or between purebred and mixbred dogs (P = 0.16; P = 0.29). Degenerative joint disease (DJD) was the most common radiographic manifestation of HD and there appeared to be a threshold at 12 months of age after which the presence of DJD was the primary diagnostic criteria.

Evaluation of a radiographic caudolateral curvilinear osteophyte on the femoral neck and its relationship to degenerative joint disease and distraction index in dogs

OBJECTIVE

To determine prevalence of a radiographic caudolateral curvilinear osteophyte (CCO) on the femoral neck in various breeds and age groups of dogs and to evaluate its contemporaneous relationship with degenerative joint disease (DJD) and distraction index (DI).

DESIGN

Cross-sectional prevalence study.

ANIMALS

25,968 dogs, including 3,729 German Shepherd Dogs, 4,545 Golden Retrievers, 6,277 Labrador Retrievers, and 1,191 Rottweilers.

PROCEDURE

Data from the University of Pennsylvania Hip Improvement Program database were analyzed, including ventrodorsal hip-extended, compression, and distraction radiographs. The CCO and radiographic signs of DJD were considered independent events and were interpreted as either present or absent. Statistical methods were used to evaluate the CCO as a possible risk factor for DJD and assess its association with DI, as measured by use of distraction radiography.

RESULTS

When all breeds were pooled, DJD was detected in 8.6% of dogs, and the CCO was detected in 21.6% of dogs. Among dogs with a CCO, 25.1% had radiographic evidence of DJD. Among dogs without a CCO, only 4% had DJD. Dogs with a CCO were 7.9 times as likely to have DJD as were those without a CCO. Additionally, DI, weight, and age were significant risk factors for the CCO.

CONCLUSION AND CLINICAL RELEVANCE

Results confirm the contemporaneous association between the CCO and DJD and that passive hip laxity, as measured by use of the DI, is associated with both the CCO and DJD.

Evaluation of risk factors for degenerative joint disease associated with hip dysplasia in German Shepherd Dogs, Golden Retrievers, Labrador Retrievers, and Rottweilers

OBJECTIVE

To determine whether age, breed, sex, weight, or distraction index (DI) was associated with the risk that dogs of 4 common breeds (German Shepherd Dog, Golden Retriever, Labrador Retriever, Rottweiler) would have radiographic evidence of degenerative joint disease (DJD) associated with hip dysplasia.

DESIGN

Cross-sectional prevalence study.

ANIMALS

15,742 dogs.

PROCEDURE

Hips of dogs were evaluated radiographically by use of the ventrodorsal hip-extended view, the compression v ew, and the distraction view. The ventrodorsal hip-extended view was examined to determine whether dogs had DJD. For each breed, a multiple logistic regression model incorporating age, sex, weight, and DI was created. For each breed, disease-susceptibility curves were produced, using all dogs, regardless of age, and dogs grouped on the basis of age.

RESULTS

Weight and DI were significant risk factors for DJD in all breeds. For German Shepherd Dogs, the risk of having DJD was 4.95 times the risk for dogs of the other 3 breeds combined. In all breeds, the probability of having DJD increased with age.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that the probability of having hip DJD increased with hip joint laxity as measured by use of DI. This association was breed-specific, indicating that breed-specific information on disease susceptibility should be incorporated when making breeding decisions and when deciding on possible surgical treatment of hip dysplasia.

Estimation of genetic population variables for six radiographic criteria of hip dysplasia in a colony of Labrador Retrievers

OBJECTIVE

To estimate genetic population variables for 6 radiographic criteria of canine hip dysplasia (CHD).

ANIMALS

664 full- and half-siblings from a colony of Labrador Retrievers.

PROCEDURE

Heritability estimates and genetic correlations were calculated for 6 radiographic criteria of CHD. Two evaluation protocols were compared: the grade of the most severely affected hip joint and the sum of the scores for both hip joints. The predictive performance of estimated breeding values was also evaluated.

RESULTS

The overall prevalence of CHD (Federation Cynologique Internationale grades C, D, and E) was 29.6%. Median age at radiographic examination was 377 days. Heritability for the total CHD grade, Norberg angle (NA), coverage of the femoral head (COV), craniodorsal acetabular rim (ACR), subchondral bone sclerosis (SUBCH), shape of the femoral head and neck (FHN), and osteoarthritic changes at the insertion site of the joint capsule (JC) was estimated as follows: 0.44, 0.43, 0.46, 0.37, 0.32, 0.21, and 0.05, respectively. Heritability estimates were slightly higher for the sum of the scores for both hip joints. If NA and COV were included as fixed effects in the model for the dependent variables ACR, SUBCH, FHN, and JC , then heritability of these traits significantly decreased (0.08 to 0.15). High scores of NA and COV lead to a significant increase of the scores of the remaining criteria.

CONCLUSIONS AND CLINICAL RELEVANCE

Canine hip dysplasia is heritable to a moderate degree. Signs of subluxation revealed the highest heritability estimates. The criteria ACR, SUBCH, FHN, and JC were strongly influenced by NA and COV.

Heritability and epidemiology of canine hip-dysplasia score in flat-coated retrievers and Newfoundlands in the United Kingdom

Hip dysplasia (malformation of the coxofemoral joint) in dogs is a major health problem for which the British Veterinary Association (BVA) had set up a control scheme in 1965. Based on scoring nine components of the radiographs of both the left and right joints, the degree of hip joint malformation is now quantified by an overall hip score (a measure of the condition of the hip joint). The hip scores of 1258 flat-coated retrievers and 1566 Newfoundlands (registered with The Kennel Club in the United Kingdom) were analysed after merging with Kennel Club pedigree data for 19036 flat-coated retrievers registered by 1995 and 14336 Newfoundlands registered by 1997. The merged data included the animal's identity, date of birth, sex and hip scores and also similar records for the dog's relatives including the hip score if the relative had been tested. In recent years, breeding has been increasingly from tested parents. There has been some reduction in offspring hip scores - presumably because breeders avoided breeding from males with very high scores. However, a much greater reduction in offspring hip score would be achieved by stricter science-based selection of potential sires and dams. Regression modelling quantified the positive relationship between offspring and parental hip scores. The genetic heritability of hip scores was large and significant in both breeds (particularly from dams). The breeders in UK tended to use healthy sires for breeding but they have taken less care in selecting dams. Our regression models emphasise the need for both sires and dams, particularly dams, to be healthy with very small hip scores.

Estimates of genetic parameters for hip and elbow dysplasia in Finnish Rottweilers

Data from 2,764 Rottweiler dogs born from 1987 to 1996 were analyzed with a Restricted Maximum Likelihood procedure using a mixed linear animal model to obtain variance component estimates for hip and elbow dysplasia. The data included 2,764 hip dysplasia and 2,278 elbow dysplasia records. Hip joints were scored as normal (0), borderline (1), slight (2), moderate (3), and severe (4, 4.5, and 5) hip dysplasia. Elbow joints were graded normal or borderline (0), slight (1), moderate (2), and severe (3) elbow dysplasia. The mean for the hip scores was 1.07 and for the elbow scores .60. Environmental effects influencing hip dysplasia were age, birth year, birth year x season interaction, and experience of the veterinarian responsible for x-raying the dog. For elbow dysplasia, statistically significant effects were age, birth year, sex of the dog, and panelist responsible for each screening. Estimates of heritability for hip and elbow dysplasia were .58 +/- .04 and .31 +/- .04, respectively, with a genetic correlation of .37 +/- .08 between the traits. Genetic improvement of almost one genetic standard deviation was observed in both traits during the 10 yr covered by the data.

Factors affecting hip dysplasia in German shepherd dogs in Finland: efficacy of the current improvement programme

Hip dysplasia records from 10,335 German shepherd dogs were used to estimate environmental effects and predict breeding values and genetic change achieved with the Finnish Kennel Club's breeding programme. The best linear unbiased prediction (BLUP) procedure was used for the analysis. No clear genetic improvement could be found during the study period (1985 to 1997). This might be due to ineffective selection for good hips. Significant environmental effects included year and month of birth, panellist, screening age and the effect of the genetic group of offspring from imported versus non-imported sires. In order to make the breeding programme more effective, BLUP breeding values should be used instead of phenotypic selection.

Controlling canine hip dysplasia in Finland

The aim of the study was to evaluate the Finnish Kennel Club's hip-dysplasia screening and control programs. As a retrospective study, records of hip-dysplasia screening of 69,349 dogs in 22 breeds that were born in 1988-1995 were analyzed and compared to data from prior to 1988. In most breeds, no significant changes in dysplasia prevalence could be found. In English cocker spaniels, golden and Labrador retrievers and Rottweilers a significant decrease - but in boxers, Dobermans, German Shepherd dogs and rough collies a significant increase - in prevalence was detected. In flat-coated retrievers overall prevalence increased - but the prevalence of severe hip-dysplasia decreased significantly during the study period. The present control program has not resulted in fast progress. Selecting against hip-dysplasia cannot be expected to be very effective, when based only on mass selection on phenotypic observations. Predicted breeding values based on progeny testing would probably give better results. Also, breeders' compliance and commitment to programs is not always high and other selection criteria in breeding are thought to be more important. Modern society has high demands for animal welfare and consumer issues, and breeders and kennel societies should pay more attention to health issues in breeding pedigreed dogs.

[Epidemiologic and genetic studies of canine hip dysplasia in a population of Labrador retrievers: a study over 25 years]

The occurrence of canine hip dysplasia (CHD) was analyzed in a colony of 738 Labrador Retrievers between 1972 and 1996. Of these dogs, 86.3% were radiographically examined for hip dysplasia. The overall prevalence of CHD was 31.3% during the study period of 25 years. Between 1972 and 1980, the prevalence of CHD was 57.9%. It decreased to 14.9% between 1991 and 1996. Univariate and multivariate logistic regression models were developed to identify the influence of potential risk factors for CHD such as age at examination, gender, color, year and season of birth, litter size, order of birth, birth weight, body weight and daily weight gain. Birth year and age at examination proved to be significant risk factors. No significant association was found between CHD and elbow dysplasia. Of the dogs diagnosed with CHD, 18% showed dysplastic changes only, without radiographic signs of secondary osteoarthritis (OA). The Norberg angle (NA) proved to be a significant risk factor for coxofemoral osteoarthritis with a moderate negative correlation between OA and NA. Finally, genetic effects were calculated in a mixed model. Heritability (h2) of CHD was estimated at 0.53 (SE = 0.17) for paternal half siblings. The proportion of the common environment of a litter to the total variance was estimated at C2 = 0.03.

Reliability of the hip distraction index in two-month-old German shepherd dogs

OBJECTIVE

To determine whether distraction index (DI), a measure of passive hip joint laxity, at 2 months of age was predictive of DI at 4 or 12 months of age in German Shepherd Dogs.

DESIGN

Prospective cohort study.

ANIMALS

45 German Shepherd Dogs.

PROCEDURE

DI was measured at 2, 4, and 12 months of age. At the same times, a standard ventrodorsal radiographic projection of the pelvis with the hip joints extended was obtained and examined for evidence of degenerative joint disease (DJD). To facilitate radiographic positioning, dogs were sedated or anesthetized.

RESULTS

DI at 2 months of age was not significantly correlated with DI at 4 or 12 months of age. However, DI at 4 months of age was correlated with DI at 12 months of age. The proportion of dogs with DI > or = 0.3 at 12 months of age that had radiographic evidence of DJD by 12 months of age (13/22; 59%) was significantly greater than the proportion of dogs with DI < 0.3 at 12 months of age that had radiographic evidence of DJD by 12 months of age (1/9; 11%).

CLINICAL IMPLICATIONS

For German Shepherd Dogs, DI at 2 months of age was not sufficiently reliable to predict DI at 4 and 12 months of age; however, DI at 4 and 12 months of age were comparable. We recommend that, for German Shepherd Dogs, DI not be measured before 4 months of age and that particularly for breeding dogs, DI be remeasured after maturity to confirm DI obtained at earlier ages. Studies including other breeds of dogs should be done to determine the youngest reliable age to initiate hip joint screening.

Retrospective cohort study of changes in hip joint phenotype of dogs in the United States

OBJECTIVE

To determine whether there had been a significant improvement in hip joint phenotype of dogs in the United States by comparing results of evaluations done by the Orthopedic Foundation for Animals of dogs born between 1972 and 1980 with those of dogs born between 1989 and 1992 and determining whether there had been an increase in the percentage of dogs classified as having excellent hip joint phenotype.

DESIGN

Retrospective cohort study.

SAMPLE POPULATION

270,978 evaluations.

PROCEDURE

Numbers and percentages of dogs classified as having excellent hip joint phenotype during each period and change between periods in percentages of dogs classified as having excellent hip joint phenotype were calculated.

RESULTS

Percentage of dogs born between 1989 and 1992 that were classified as having excellent hip joint phenotype (15,289/143,668; 10.64%) was significantly higher than percentage of dogs born between 1972 and 1980 that were classified as having excellent hip joint phenotype (9,960/127,310; 7.82%). The increase in percentage of dogs classified as having excellent hip joint phenotype was significantly higher for male (51%) than for female (27%) dogs.

CLINICAL IMPLICATIONS

Results suggest that there has been an improvement in the hip joint phenotype of dogs in the United States between the 1970s and early 1990s and that the improvement has been greater among male than among female dogs.

Within- and between-examiner repeatability of distraction indices of the hip joints in dogs

OBJECTIVE

To evaluate in vivo repeatability of the distraction index method of evaluating hip joint laxity in dogs.

ANIMALS

31 two-year-old Labrador Retrievers.

PROCEDURE

Each dog was anesthetized and radiographically evaluated for hip joint laxity 4 times: twice by an experienced examiner and twice by an examiner who had no previous knowledge of or training in the technique prior to the first day of testing. Distraction indices (DI) were determined from the radiographs and intraclass correlation coefficients were calculated to evaluate the repeatability of DI measurements between and within examiners.

RESULTS

Intraclass correlation coefficients were high (range, 0.85 to 0.94). Lower limits of the 95% confidence intervals for the intraclass correlation coefficients ranged from 0.75 to 0.89.

CONCLUSIONS

Between- and within-examiner repeatabilities of DI measurements were high, suggesting that the technique is clinically reliable.

CLINICAL RELEVANCE

Distraction index is a reliable measure of hip joint laxity and a good predictor of the risk of development of degenerative joint disease associated with hip dysplasia in dogs. Establishment of high repeatability of DI measurements suggests that the stress-radiographic method may be used by multiple examiners with the expectation of comparable and consistent results.

A review of the progress in canine hip dysplasia control in Britain

Results of the British Veterinary Association/Kennel Club program for controlling canine hip dysplasia (CHD) were reviewed for 6 breeds to determine whether there had been any progress in reducing the prevalence of CHD. Although there was a decrease in mean hip dysplasia score for some of the 6 breeds when results for the 1991 to 1995 period were compared with those for 1987 to 1990, there were not any consistent trends in 5 of the breeds, and there was a clear worsening of the mean hip score in Siberian Huskies. In general terms, not only has there been a steady increase in the percentage of parents that were scored or, more accurately, an increase in the use of scored parents when breeding, but in broad terms the weighted mean score for the parents was lower (ie, better) than the mean score for all dogs in the breed during each period. In all breeds, there appeared to have been some selection to reduce total hip score, but in all but 1 instance, the expected result was not achieved, with actual values being higher (ie, worse) than those expected from theory. If the incidence of CHD is to diminish in Britain, then, as a first step, the Kennel Club must insist that, in affected breeds, only progeny of scored parents may be registered. Thereafter, a gradual tightening of the parental scores that will be accepted in each breed should be attempted, and best linear unbiased predictor-type indices should be established and applied to sires and dams to ensure wider usage of the better parents.

Advances in diagnosing canine hip dysplasia

The DI method was developed, at least in part, because of perceived variations among radiologists in regard to subjective hip scores assigned to radiographs. It also was recognized that the prevalence of CHD among many dog breeds was disturbingly high, despite efforts to lower the prevalence using subjective score as a selection criterion. The DI method was developed on the basis of results of mechanical testing of cadaver hip joints, which accomplished 3 principal objectives. First, it showed that when the hip joint is in the standard, hip-extended, internally rotated position, passive laxity is minimized. Second, it showed that passive laxity was maximized when the hip joint is in the neutral position. Third, it demonstrated the sigmoidal nature of the load/displacement curve for the hip joint in the neutral position, which suggested that high repeatability from examiner to examiner in regard to DI could be expected without the need to standardize applied force. The mean and range of DI were shown to vary from 1 breed to the next, but within an individual dog, DI appears to remain constant (within limits of scientific acceptability and clinical applicability) from 16 weeks of age. Passive hip laxity measured on the distraction view is, on average, 2.5 to 11 times greater than that measured on the standard, hip-extended radiographic view. Performance Borzois and Greyhounds, which have an extremely low prevalence of CHD, uniformly have tight hip joints (DI < 0.3), and mean DI for dog breeds that have a high prevalence of CHD is significantly greater than mean DI for Borzois and Greyhounds. However, individual dogs that have DI < 0.3, even though members of breeds prone to CHD, have a low risk of developing DJD. Some, but not all, dogs with DI > 0.3 will develop DJD by 3 years of age, and DI has been shown to be the principal risk factor for development of DJD. Susceptibility to development of DJD appears to be breed-specific. For example, given equivalent DI, German Shepherd Dogs are more at risk for developing DJD than are Rottweilers. Heritability of DI is higher than that of the subjective hip score; thus, selection pressure based on DI should result in faster genetic change than selection pressure based on subjective hip scores. Finally, the DI method has been performed on approximately 14,000 dogs, some of which were evaluated multiple times. It is apparent that this method is no more harmful than the standard, hip-extended radiographic method or palpation performed as part of a routine orthopedic examination.

Variations in composition of cartilage from the shoulder joints of young adult dogs at risk for developing canine hip dysplasia

OBJECTIVE

To determine whether the composition of cartilage from the shoulder joints of dogs varied with the risk of developing canine hip dysplasia (CHD).

DESIGN

Observational study.

ANIMALS

12 skeletally mature (approx 1 year old) Labrador Retrievers.

PROCEDURE

Dogs were classified as having a low, moderate, or high risk of developing CHD on the basis of distraction indices. Cartilage was harvested from the craniolateral and weight-bearing regions of the humeral heads, and wet weight per unit area and dry, glycosaminoglycan, and fibronectin contents were determined.

RESULTS

Glycosaminoglycan and dry contents did not vary among risk groups. For cartilage from the craniolateral region of the humeral head, wet weight per unit area and fibronectin content increased as risk of developing CHD increased. Wet weight and fibronectin content of cartilage from the weight-bearing region of the humeral head did not vary among risk groups.

CLINICAL IMPLICATIONS

Dogs that have a high risk of developing CHD are also more likely to develop osteoarthritis of the shoulder joint. The observed increases in wet weight per unit area and fibronectin content in cartilage from the craniolateral region of the humeral head in dogs at a high risk of developing CHD may be early sings of incipient osteoarthritis.

Genetics of canine hip dysplasia

OBJECTIVE

To document genetic progress in improving hip quality of dogs maintained in a closed breeding colony to produce dogs for training as guides for blind people.

DESIGN

Prospective analysis of hip quality records from a breeding trial that encompassed 3 full generations and included some dogs born into the fourth and fifth generations.

ANIMALS

Hip quality was assessed for 2,037 German Shepherd Dogs and 1,821 Labrador Retrievers from 1980 to 1996.

PROCEDURE

A subjective hip score assigned by 1 radiologist was used to assess hip quality during the study period. In the past 8 years, the distraction index was also used. Genetic change was produced by selecting a small percentage of dogs to be parents of the next generation. Dogs were selected to become parents of the next generation on the basis of estimated breeding values. These were calculated by combining observed values of individual dogs with known relationships in the population pedigrees to predict which dogs were the best candidates for selection as parents.

RESULTS

In < 5 generations of selection, the percentage of German Shepherd Dogs with canine hip dysplasia at 12 to 16 months of age decreased from 55 to 24%. Among Labrador Retrievers, the percentage decreased from 30 to 10%.

CLINICAL IMPLICATIONS

This report gives practitioners documented proof that genetic selection will work to improve hip quality. Dog breeders must be advised to be patient, however, to allow enough generations to elapse to make meaningful genetic change.

Prevalence and inheritance of and selection for hip dysplasia in seven breeds of dogs in Sweden and benefit: cost analysis of a screening and control program

OBJECTIVE

To determine the prevalence and changes over time in the prevalence of hip dysplasia; to ascertain whether prevalence or severity of hip dysplasia was associated with sex of the dogs, age at which coxofemoral joint status was evaluated, or ancestral background; to determine the effects of selective breeding; and to conduct an economic evaluation of the hip dysplasia program operated by the Swedish Kennel Club.

DESIGN

Analysis of radiographic evaluations of coxofemoral joint conformity.

ANIMALS

83,229 dogs from 7 breeds registered by the Swedish Kennel Club.

PROCEDURE

All radiographs were scrutinized by a single radiologist (LA), and coxofemoral joint conformation was classified as normal or dysplastic, with the degree of dysplasia classified as 1,2,3, or 4.

RESULTS

Decreasing prevalence of hip dysplasia corresponding to selection of breeding stock and high heritabilities was found. Sex differences were documented in 3 of the breeds. This was interpreted as breed differences in the distribution of genes related to hip dysplasia. Economic analyses showed that costs of screening and registration of coxofemoral joints was less than the value of dogs estimated to have been saved from moderate, severe, or very severe hip dysplasia in 6 of the breeds.

CLINICAL IMPLICATIONS

Documented effects of age suggest that all dogs should be screened at the same age, rather than screening a few dogs at an older, more revealing age. In screening and control programs based on an open registry with access to family records, decreasing prevalence of hip dysplasia can be expected, and related to selection of breeding stock.

Five-year longitudinal study on limited food consumption and development of osteoarthritis in coxofemoral joints of dogs

OBJECTIVE

To examine the effects of limited food intake on frequency and severity of osteoarthritis in coxofemoral joints of labrador Retrievers.

DESIGN

Dogs were paired according to gender and body weight, within each litter at 8 weeks of age. One dog of each pair was fed ad libitum. The limit-fed pairmate was fed 75% of the amount eaten the previous day by the ad libitum-fed counterpart.

ANIMALS

48 Labrador Retrievers.

PROCEDURE

All dogs received the same diet. Radiographic evaluation of coxofemoral joints for frequency and severity of osteoarthritis were made when dogs were 4 and 6 months and 1, 2, 3, and 5 years old.

RESULTS

Radiographic evaluation for osteoarthritis indicated greater frequency and more severity of osteoarthritis in the ad libitum-fed group of dogs.

CLINICAL IMPLICATIONS

Analysis of data suggested that limit feeding of dogs over a 5-year period minimizes development of osteoarthritis in the coxofemoral joints.

Prevalence and inheritance of and selection for elbow arthrosis in Bernese mountain dogs and Rottweilers in Sweden and benefit: cost analysis of a screening and control program

OBJECTIVE

To determine the prevalence and charges over time in the prevalence of elbow arthrosis in Bernese Mountain Dogs and Rottweilers, to ascertain whether prevalence or severity of elbow arthrosis was associated with sex of the dogs, age at the time of elbow joint examination, or ancestral background, to determine the effects of selective breeding, and to conduct an economic evaluation of the elbow arthrosis program operated by the Swedish Kennel Club.

DESIGN

Analysis of radiographic evaluations of elbow joint conformity.

ANIMALS

4,515 dogs from 2 breeds registered by the Swedish Kennel Club.

PROCEDURE

All radiographs were scrutinized by a single radiologist (LA), and elbow joint conformation was classified as normal or arthrotic, with the degree of arthrosis classified as 1, 2, or 3.

RESULTS

Decreasing prevalence of elbow arthrosis corresponding to selection of breeding stock and high heritabilities was found. Sex differences were documented in both breeds, but with contradictory directions. This was interpreted as breed differences in the distribution of genes related to elbow arthrosis. Economic analyses showed that costs of screening and registration of elbow joints was less than the value of dogs estimated to have been saved from moderate and severe elbow arthrosis in both breeds.

CLINICAL IMPLICATIONS

Documented effects of age suggest that all dogs should be screened at the same age, rather than screening a few dogs at an older, more revealing age. In screening and control programs based on an open registry with access to family records, decreasing prevalence of elbow arthrosis can be expected, and related to selection of breeding stock.

[Analysis of development of hip joint dysplasia in dogs]

Hip joint dysplasia in dogs occurs mainly in large and heavy breeds. It brings about changes on the acetabulum (socket) and the head of thigh bone, thus causing pain, tiredness, refusal to jump and refusal of increased activity. Even though presently the genetic basis of development of this disease, numerous literary sources indicate existence of pre-disposing factors that facilitate development in later stages of life. Diet and unbalanced development of skeleton and support tissues-ligaments, joint capsule and musculature also have the effect on development of dysplasia. We have analyzed acquired results of X-ray examination of dogs-German shepherds. The size of the group was 4 206 and the examination was aimed at incidence of hip-joint dysplasia during the period of 1977-1995 in the Slovak Republic. We have found out that in 1977 there were 70.7% positive cases out of the total number of examined individuals. Gradual exclusion of dogs with heavier grades of dysplasia (D, E) decreased occurrence of dysplasia to current rate of 40.8%. We considered it to be a high incidence rate. Internal structure of the positive group has changed. The number of dogs with the lightest grade of dysplasia (B) has increased, while the number of heavier grade dysplasia (C, D, E) decreased. In other breeds of dogs, of which more than 20 have been examined at the clinic, the following results have been acquired: Slovak chuvash-32%, Bavarian and Hannover bloodhound-30.6%, Rotweiler-28.6%, Newfoundland dog-26.3%, Bern sheep-dog-13.6%. At the same time we analyze the incidence of dysplasia in dogs whose parents were negative. Group of descendants of 11 negative males and 28 females consisted of 73 dogs. Through x-ray examination, 42.5% of dogs were found to have dysplasia B, C and D at the age of 1 year.

Comparison of susceptibility for hip dysplasia between Rottweilers and German shepherd dogs

Passive laxity of the coxofemoral joints, as measured quantitatively by radiographing the joints under stress, has been shown to be an accurate measure of the risk for developing degenerative joint disease (DJD) of the coxofemoral joints. Seventy-four Rottweilers between 12 and 40 months old were evaluated subjectively for radiographic evidence of DJD, using the ventrodorsal view of the pelvis with the coxofemoral joints fully extended and the knees internally rotated (standard hip-extended view). Effect of age, sex, weight, and distraction index on the risk of developing DJD was evaluated by use of a logistic regression model. Results were compared with those from a group of German Shepherd Dogs. Results indicated that in Rottweilers the distraction index was the only statistically significant predictor of the risk of developing DJD of the coxofemoral joint. When German Shepherd Dogs were included in the model, they had a significantly greater risk of developing DJD than did Rottweilers. This finding provides further support for the theory that there are differences in disease susceptibility among breeds and emphasizes the need to develop disease susceptibility curves for all breeds affected by hip dysplasia to facilitate accurate, scientifically based recommendations for breeding or treatment.

Hip dysplasia in dogs in relation to their month of birth

German wirehaired pointers, English, Irish and Gordon setters, and labrador retrievers that were puppies during the spring and summer had a significantly lower incidence of hip dysplasia than those growing up during the autumn and winter. However, golden retrievers and German shepherd dogs did not show the same seasonal pattern of incidence of hip dysplasia.

Trends in hip dysplasia control: analysis of radiographs submitted to the Orthopedic Foundation for Animals, 1974 to 1984

From 1974 through 1984, the Orthopedic Foundation for Animals evaluated 143,218 radiographic submissions representing 151 breeds of dogs. All breeds from which there were 35 or more evaluations had some frequency of dysplasia. Seventy breeds, each with over 100 submissions, were tabulated and ranked according to frequency of hip dysplasia. Frequency of dysplasia varied from 0.6% in the Borzoi to 46.9% in the Saint Bernard. These data were compared with data obtained earlier (1966 to 1973) on evaluations in 38 breeds for changes in frequency. There was significant (P less than 0.05) reduction in frequency of dysplasia in 27 breeds, a significant (P less than 0.05) increase in frequency in only 1 breed (German Shorthaired Pointer), and no significant change in frequency in 10 breeds. The median significant decrease was 22.4%, and the range was from 3.1% in the Chesapeake Bay Retriever to 48.7% in the Keeshond. The reduction in frequency of hip dysplasia demonstrated the value of a control program. There were 5 breeds with a significant (P less than 0.05) decrease in frequency of dysplasia that had over 5,000 evaluations from 1974 to 1984. The decreases in frequency were independent of changes in American Kennel Club registrations for these breeds (a dramatic decline in registrations for the German Shepherd Dog and Old English Sheepdog, and a dramatic increase for the Rottweiler, Golden Retriever, and Labrador Retriever). Frequency regressed linearly in the German Shepherd Dog and Old English Sheepdog, but regressed nonlinearly in the other 3 breeds. The percentage reduction in frequency from the base frequency (1966 to 1973) for these breeds was 17.5% for the German Shepherd Dog, 23.1% for the Old English Sheepdog, 9.1% for the Rottweiler, 10.1% for the Golden Retriever, and 6.8% for the Labrador Retriever.