Risk factors for hip-related clinical signs in a prospective cohort study of four large dog breeds in Norway

We conducted a prospective cohort study including privately owned dogs from the breeds Newfondland (NF), Labrador Retriever (LR), Leonberger (LEO), and Irish Wolfhound (IW) followed from birth until age 9 yrs. We wanted to investigate whether radiological hip dysplasia status given at approximately age 12-18 mos and other factors during growth influenced development of clinical signs due to hip-joint disease necessitating veterinary consultation. Whether or not such signs occurred due to hip dysplasia or due to secondary or primary DJD could not be distinguished, and we therefore used the term "owner-reported veterinary-diagnosed hip-related clinical signs" ("the event"). The included dogs were followed from birth to the event or until a maximum of 9 yrs of age. Our objectives were to describe breed differences in time to incidence and to evaluate potential risk factors for the time to event. We used Kaplan-Meier curves to describe time to incidence, and potential risk factors were assessed by use of a Cox proportional-hazards model. We enrolled 494 dogs from 103 litters, and 46 dogs were reported as having had the event during the observation period. We observed a significant time-varying effect (TVE): LR and LEO developed clinical signs later in life than NF. If the radiological hip status was either mild, moderate, or severe the hazard of experiencing the event was significantly increased. Access to off-leash exercise at age 12 mos decreased the hazard of the event, and the hazard varied by litter. The findings supported the hypothesis that radiological hip status at screening and exercise conditions during growth influenced the time to incidence of the event and that there were breed differences in time to the event.     

Impact of sedation method on the diagnosis of hip and elbow dysplasia in Swedish dogs

Our objective was to investigate the effect of sedation method on the screening result for hip and elbow dysplasia. The study was based on a questionnaire survey of routines for hip and elbow screening at Swedish veterinary clinics and results of hip and elbow status, for eight breeds (Bernese Mountain Dog, Boxer, German Shepherd Dog, Golden Retriever, Labrador Retriever, Newfoundland, Rottweiler, and Saint Bernard) recorded by the Swedish Kennel Club. In total 5877 and 5406 dogs examined for hip and elbow dysplasia, respectively, from January 2002 through March 2003 were included. We used logistic regression to examine whether the type of chemical restraint used for sedation affected the screening result for hip and elbow dysplasia. In addition to sedation method, the effects of veterinary clinic, sex, breed, and age at screening were studied.

The type of chemical restraint used for sedation affected the screening result for hip but not for elbow dysplasia. Acepromazine gave less than half the odds of hip dysplasia compared with medetomidine and butorphanol (the most common method), medetomidine alone or xylazine. Females had about 25% higher odds for developing hip dysplasia whereas males had almost 40% higher odds for developing elbow dysplasia. Saint Bernard, Newfoundland and German Shepherd Dog had the highest odds of developing hip dysplasia, whereas Rottweiler and Labrador Retriever had the lowest odds. Boxer had the lowest risk for elbow dysplasia, followed by Labrador Retriever. Saint Bernard and Rottweiler had the highest odds of elbow dysplasia. Increasing age increased the odds of both hip and elbow dysplasia, by about 2.5% per month.

Following the results in this study, recording of the type of chemical restraint used for sedation during hip screening has now become mandatory in Sweden. This makes it possible to account for the effect of sedation method in a model for prediction of breeding values for hip dysplasia.     

Association between radiographic assessment of hip status and subsequent incidence of veterinary care and mortality related to hip dysplasia in insured Swedish dogs

Our objective was to evaluate the association between grading of hip status as assessed by radiographic examination (hip screening) and subsequent incidence of veterinary care and mortality related to hip dysplasia (HD) in five breeds of insured dogs in Sweden. Screening results for hip status from the Swedish Kennel Club and data on veterinary care and mortality from the insurance company Agria were merged based on the registration number of the dog. Dogs of five breeds (Bernese Mountain Dogs, German Shepherds, Golden Retrievers, Labrador Retrievers, and Rottweilers) screened during 1995–2004 and covered by an insurance plan for veterinary care or life at the time of screening were included. The study populations included between 1667 and 10,663 dogs per breed. Breed-specific multivariable Cox proportional-hazards analyses were performed to evaluate the impact of radiographic hip status on time from hip screening to first HD-related veterinary and life claim, respectively. The effects of gender, birth season, and a time-varying covariate of year were also studied. Additional analyses, on the five breeds combined, were performed to investigate the effects of hip status, breed, and the interaction between hip status and breed. The effect of hip status was highly significant (P < 0.001) for both life and veterinary claims related to HD in all five breeds with increased hazard ratio (HR) for deteriorating hip status. Dogs with moderate or severe hip status at screening had a markedly increased hazard of HD-related veterinary care and mortality compared with dogs assessed as free or mild. The time-varying covariate of year showed a significantly higher HR in the last time period for German Shepherds and Labrador Retrievers in the analyses of veterinary claims. In the analyses on all five breeds, German Shepherds had the highest HR for both veterinary care and mortality related to HD, followed by Bernese Mountain Dogs. Golden and Labrador Retrievers had the lowest HR. The effect of hip status on the hazard was the same irrespective of breed. However, as a consequence of differences between breeds in overall risk, the predictive ability of screening results for subsequent incidence of HD-related problems for individual dogs was breed-dependent. Based on the strong association between radiographic hip status and incidence of HD-related veterinary care and mortality, and the previously reported moderate heritability of hip status, we conclude that selection based on screening results for hip status can be expected to reduce the risk of HD-related clinical problems.     

Role of the Orthopedic Foundation for Animals in the control of canine hip dysplasia.

The objectives of the Dysplasia Control Registry, the procedure for submitting radiographs, and the radiographic evaluation process are described. The results from the radiographic evaluation of 321,183 dogs are reported by hip phenotypic ratings and breed frequency of canine hip dysplasia. Breeds at risk are documented. Comparison of dogs born between 1981 and 1988 with those born between 1972 and 1980 demonstrated that the frequency of canine hip dysplasia was reduced in 79% of breeds, and the frequency of excellent hips was increased in 88% of the breeds. Reliability of preliminary hip evaluations of dogs under 24 months of age is reported to vary by breed, and the results of 9,161 preliminary evaluations are documented.     

Comparison of two canine registry databases on the prevalence of hip dysplasia by breed and the relationship of dysplasia with body weight and height

OBJECTIVE: To compare the results of 2 canine registries for classification of the hip joints for dysplasia by breed, and to relate the percentage of dysplastic dogs with body metric characteristics. SAMPLE POPULATION: Data on the ranking order of hip dysplasia by breed from 2 registries for 156 dog breeds. PROCEDURES: The prevalence of hip dysplasia listed by the Orthopedic Foundation for Animals (OFA) and the breed mean score according to the list of the British Veterinary Association (BVA) Kennel Club Hip Dysplasia scheme were related to weight and height as well as the body mass index (BMI; kg/m(2)) by breed. RESULTS: The OFA ranking order and the percentage of dysplastic dogs were highly correlated with the BVA mean score (rho = 0.74). A significant correlation was found between the prevalence of hip dysplasia and the BMI (r = 0.63). Receiver operating characteristic curve analysis revealed that the highest area under the curve, corresponding to the best discrimination, was at a BMI of 110 kg/m(2) with a criterion value of 15% dysplastic dogs (area under the curve, 0.89). Because the ratio of dogs in the positive and negative groups reflected the prevalence of the condition among breeds in the OFA database, the positive likelihood ratio was 9.32 and the negative likelihood ratio was 0.24. CONCLUSION AND CLINICAL RELEVANCE: The OFA statistics and the BVA mean scores reflected the prevalence of hip dysplasia among dog breeds. Body mass index accurately discriminated between breeds with high or low prevalence of hip dysplasia.     

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.     

Comparison of two classification protocols in the evaluation of elbow dysplasia in the dog

The incidence of elbow disease based solely on arthrosis (ARTH) score was compared with a protocol using a combination of ARTH score plus a score for primary lesions (ED score). The population of dogs studied included 425 Bernese mountain dogs and 22 dogs of other breeds. The overall agreement between the two systems was high. However, 12 per cent of ARTH-score negative cases were positive using the ED score. This difference was statistically significant (P<0·005). The female:male ratio of the dogs missed using the ARTH score was 2:1. The proportion of dogs affected with arthrosis increased with age, male dogs being affected more frequently. The development of arthrosis depends not only on age and breed, but probably also on gender. Thus, screening for elbow dysplasia should be based on at least two radiographic projections, including arthrosis and primary lesions. As the vast majority of dogs in this study were Bernese mountain dogs, conclusions are valid only for this breed.     

Distraction index as a risk factor for osteoarthritis associated with hip dysplasia in four large dog breeds*

Objective : To determine if age, breed, gender, weight or distraction index (DI) influenced the risk of radiographic osteoarthritis (OA) of canine hip dysplasia (CHD) in four common dog breeds; the American bulldog, Bernese mountain dog, Newfoundland and standard poodle. Materials and Methods : This was a cross sectional prevalence study with 4349 dogs. Canine hips were evaluated using 3 radiographic projections: the hip-extended view, the compression view and the distraction view. The hip-extended view was examined for the presence of OA. The PennHIP distraction view was utilized to calculate the DI. For all breeds, a multiple logistic regression model incorporating age, weight, gender, and DI was created. For each breed, disease-susceptibility curves grouping dogs on the basis of age were constructed. Receiver-operating characteristic (ROC) curves were developed for each breed regardless of age. Results : For all breeds, DI was the most significant risk factor for the development of OA associated with CHD. Weight and age were also significant risk factors in all four breeds, but gender was not. Clinical Significance : Results from this study support previous findings, that irrespective of breed, the probability of radiographic OA increases with hip joint laxity as measured by the DI. Breed-specific differences in this relationship, however, warrant investigation of all breeds affected by CHD to determine inherent dependency of hip OA on joint laxity. Such findings guide veterinarians in helping dog breeders to make evidence-based breeding decisions and in informing dog owners to implement preventative treatments for CHD for dogs found to be at risk.     

Incidence of canine elbow dysplasia in South Africa

In South Africa, 1919 canine elbow dysplasia grading evaluations were performed from 1999-2006. Of these 1827 were evaluated by the senior author and form the basis of this article. Each report recorded the breed, age, sex, side affected and elbow dysplasia grading. The relationship between breed, age, sex, side affected, origin of radiographs and elbow dysplasia incidence was then analysed. Statistical evaluations were performed including means and standard deviations. The Rottweiler had the highest incidence of elbow dysplasia at 55 % followed by the Bullmastiff, Chow chow, Boerboel and Golden retriever, all of which had elbow dysplasia incidences of >38%. Males were significantly more affected than females. The incidence of elbow dysplasia in the various breeds was compared with those of the Orthopaedic Foundation for Animals in the United States and was found to be much higher in South Africa.     

Hip dysplasia in the New Zealand Huntaway and Heading dog

AIMS: To conduct a practice-based survey to obtain, for the first time, data on hip dysplasia in the New Zealand working dog breeds of Huntaway and Heading Dogs. METHODS: A mailed request and personal approaches to farmer clients of Taihape and Waimarino Veterinary Services were used to recruit dog owners from the Taihape district in the North Island of New Zealand. Recruited dogs were radiographed under anaesthesia in a standard position with both hind limbs extended so that the femurs were parallel and rotated medially. The standard scoring system adopted by the New Zealand Veterinary Association (NZVA) Hip Dysplasia Scheme was used to score the hip radiographs of the dogs. RESULTS: Radiographs of the hips of 141 dogs (93 Huntaways; 48 Heading Dogs), were evaluated. The overall prevalence of hip dysplasia (defined as a combined score from both hips of 10) was 17.7%. Prevalences in Huntaways and Heading Dogs were 23.6% and 6.3%, respectively; in this sample of dogs, the odds ratio (and 95% confidence interval) for Huntaways having a score of 10 was 4.6 (1.316.0) that of Heading Dogs. The average scores were 10.8 for Huntaways and 5.9 for Heading Dogs. Huntaways were at the higher end of the breed average scores for dogs recorded in the NZVA Hip Dysplasia Scheme and Heading Dogs at the lower end. CONCLUSIONS: This preliminary study indicates that hip dysplasia may be a problem in the Huntaway breed. Investigation of the epidemiology of the condition in this breed is warranted and consideration should be given to removing high-risk Huntaways from the breeding pool.     

THE GENETICS AND EARLY PREDICTION OF HIP DYSPLASIA

SUMMARY: Four breeds of dog and crosses amongst these breeds were compared with regard to their hip dysplasia status. Both radiographic hip dysplasia at 15 months and joint laxity at 8 weeks were recorded. The prediction of radiographic hip dysplasia by joint laxity was significantly improved when breed differences were included in the prediction equation. The uses of joint laxity measurements and the genetic control of hip dysplasia are discussed.     

Comparison of two radiographic techniques for evaluation of hip joint laxity in 10 breeds of dogs

OBJECTIVE: To evaluate hip joint laxity in 10 breeds of dogs via 2 radiographic techniques. ANIMALS: 500 clinically normal dogs. DESIGN: Prospective study. PROCEDURE: Radiographs obtained via routine hip joint evaluations performed in sedated dogs of 10 popular breeds were randomly selected from a database. Measurements of distraction index (DI) and hip-extended index (HEI) on 1 hip joint radiograph randomly chosen from each dog were made. RESULTS: Mean age of dogs was 20.7 months. Mean HEI was 0.17 (range, 0.0 to 0.72) and mean DI was 0.44 (range, 0.07 to 0.96). Borzois had uniformly tight hip joints as judged by use of both methods and were considered the gold standard by which hip joint laxity was judged (all Borzois had DI < or = 0.32). Overall, DI was significantly greater than HEI. Within each breed, mean DI was always greater than mean HEI. Significant differences were detected among breeds for HEI; however, compared with DI, the magnitude of differences among breeds was less. CONCLUSIONS AND CLINICAL RELEVANCE: Distraction radiography detected the greatest range and magnitude of passive hip laxity in the 10 breeds of dogs. The difference in values between breeds known to have high prevalence of canine hip dysplasia and those in Borzois was greater for DI than for HEI. Breeds must be evaluated individually because of inherent differences in hip joint laxity.     

Mortality of purebred and mixed-breed dogs in Denmark

Causes of death and age at death of 2928 dogs are reported from a questionnaire study among members of the Danish Kennel Club (DKC) in 1997. The dogs represented 20 breeds, 15 breed-groups and a group of mixed-breed dogs. The median age at death for all dogs in the study was 10.0 years. Mixed-breed dogs had a higher median age at death (11.0 years) than the entire population, but breeds like Shetland Sheepdog, Poodle and Dachshund exceeded this age (12 years). The Bernese Mountaindog, the group of Molossian types and the Sighthounds had the shortest life span with a median age at death of 7.0 years. Old age was the most frequent reported cause of death (20.8%) followed by cancer (14.5%), behavioural problems (6.4%) accidents (6.1%), hip dysplasia (4.6%), heart diseases (4.6%) and spinal diseases (3.9%). Breed-specific proportional mortalities with 95% confidence limits are given for the six most prevalent specific causes of death.     

Meningomyelitis in dogs: a retrospective review of 28 cases (1999 to 2007)

Objectives : To characterise dogs with meningomyelitis and to compare signalment, body temperature and vaccination status to a representative control group. Methods : Dogs with meningomyelitis were identified retrospectively. Signalment, history, vaccination status, body temperature, severity of neurological dysfunction (modified Frankel score), diagnostic procedures, aetiology, survival to discharge and long‐term survival were analysed. Results : Affected dogs were younger (P<0·05) and more frequently hound or toy breeds (P<0·05) when compared with controls. Hound and toy breed dogs less than or equal to three years of age had a 13 times higher odds of meningomyelitis compared with other breeds (P<0·001). General proprioceptive ataxia, limb paresis and paraspinal hyperaesthesia were the most common clinical signs. Meningomyelitis of unknown aetiology and granulomatous meningomyelitis were the most common diagnoses. The median time to death or continued follow‐up in dogs alive at discharge was 213 days. Meningomyelitis resulted in death or euthanasia in 14 of 28 dogs. Clinical signs improved or resolved in seven of 28 dogs. Clinical Significance : Meningomyelitis is a differential diagnosis for dogs with clinical signs of myelopathy. Young dogs and toy or hound breeds seem to be predisposed. Clinical signs of meningomyelitis improve or resolve in some dogs.     

A prospective study on canine hip dysplasia and growth in a cohort of four large breeds in Norway (1998-2001)

The study-objective was to measure the effect of weight and growth related parameters on the risk of development of Canine Hip Dysplasia (CHD). The hypothesis was that heavy and fast growing dogs of large sized breeds were at increased risk of development of CHD compared to lighter and slower growing dogs. A prospective cohort study was conducted among dogs of four large breeds: Newfoundland (NF), Leonberger (LEO), Labrador retriever (LR), and Irish wolfhound (IW). The dogs were privately owned with individualized nutrition and environment, and they were followed from birth and throughout the growth period until the official screening for CHD was performed. The study sample consisted of 501 dogs from 103 litters, with the breed distribution 125 NF, 180 LEO, 133 LR, and 63 IW. Because the dogs were clustered in litters a multivariable random effects logistic regression model was used to assess statistically significant growth-related risk factors for CHD. The estimated incidence risk of CHD was 36% in NF, 25% in LEO, 20% in LR, and 10% in IW. Based upon the final multilevel model it appears that the odds of CHD among both LR and IW (odds ratio (OR) 0.22) are about one-fifth of the odds for NF. The odds for LEO (OR 0.60) are not significantly different from NF. There appeared to be an inverse relationship between body weight at 3 months of age and odds of CHD, with an OR of 0.89 (P=0.044). The degree of clustering at the litter-level was high (22.6%) and highly significant (P<0.001). Findings failed to support the hypothesis that heavy and fast growing dogs from four large sized breeds were at increased risk for development of CHD. There might be other unmeasured environmental risk factors for CHD in this cohort of dogs, although the contribution of the genetic variance to the litter-level clustering also needs further investigation.     

Genetic evaluation of elbow scores and the relationship with hip scores in UK Labrador retrievers

A linear mixed model analysis of elbow and hip score data from UK Labrador retrievers was used to estimate the heritability of elbow score (0.16-0.19) and to determine a moderate and beneficial genetic correlation with hip score (0.40). A small improvement in the genetic trend of elbow score was observed during the years 2000-2008, equivalent to avoiding only the worst 3-4% of scored dogs for breeding, but close to what may have been anticipated if the current British Veterinary Association-approved guidelines were followed. Calculations suggested that a correlated response to indirect selection on hip score may elicit a greater response than direct selection on elbow score and that the genetic trend in elbow score may be explained as a consequence of the stronger selection pressure that has been placed on hip score. Increases in the accuracy of estimated breeding values for elbow score of 4-7% for dogs with elbow data only and 7-11% for dogs with both hip and elbow score were observed from bivariate analysis of elbow and hip data. A selection index confirmed the benefits of bivariate analysis of elbow and hip score data by identifying increases in accuracy (directly related to the response to selection) of 14% from the use of optimum coefficients compared to use of hip data only. The quantified genetic correlation means that hip score effectively acts as a 'secondary indicator' of elbow score in this breed and the preponderance of hip data means that it acts as a major source of information that may be used to improve the accuracy of estimates of genetic risk for elbow dysplasia.     

A longitudinal study on growth and growth variables in dogs of four large breeds raised in domestic environments

The main objective of this study was to describe the growth patterns of 4 large dog breeds [Newfoundland (NF), Labrador retriever (LR), Leonberger (LEO), and Irish wolfhound (IW)] raised in domestic environments and concomitant changes in 2 growth-related clinical variables: total serum alkaline phosphatase (ALP) and the circumference of the distal radius and ulna (CDRU). The second objective was to investigate whether these measurements were affected by a range of independent variables like age, sex, litter number, and birth weight. Seven hundred dogs were included in the study, and BW data, separated by breed and sex, were fitted to the Gompertz function. Birth weight, adjusted for litter number, differed significantly between sexes for 3 breeds (LEO, P = 0.004; NF, P = 0.02; LR, P = 0.009) and approached significance for IW (P = 0.07). Estimated mean BW increased rapidly during the first 100 d after birth in all 4 breeds, then plateaued, with maturity being reached between 351 (female LR) and 413 d (male NF). Estimated mature BW ranged from 30.8 kg for the female LR up to 65.7 kg for the male IW. Weight gain, as expressed by the derivative of the Gompertz function, reached its peak in the smallest breed (LR) at the youngest age, 89 d for the females and 95 d for males. Log-transformed BW was significantly related to age, breed, and sex, and the age x sex and age x breed interactions. Within breeds, age, birth weight, and litter number had a significant effect on log-transformed BW. The estimated average CDRU increased from 90 d of age toward a peak at 180 d. Thereafter, CDRU declined and stabilized at about 1 yr of age. The estimated total ALP concentrations decreased from 90 to 360 d of age, after which they stabilized, at mean concentrations varying among breeds from 98 to 131 IU/L. Maximum least squares mean total ALP concentrations were found at 3 mo of age in all breeds, with the greatest least squares mean concentration in the IW breed (713 IU/L). In a mixed model analysis of the complete data set, total ALP was affected (P < 0.001) by age, breed, and the interaction of age x breed. This study described the main factors influencing growth and provided reference data for other studies, including those related to nutrition and disorders of growth.     

Methods and mortality results of a health survey of purebred dogs in the UK

Objectives : To collect information on the cause of death and longevity of dogs owned by members of the numerically largest breed clubs of 169 UK Kennel Club-recognised breeds. Methods : A cross-sectional study was carried out. Approximately 58,363 questionnaires were sent out to breed club members in 2004 (nine clubs failed to report the exact number of questionnaires sent out). Owners reported age at death and cause(s) of death for all dogs that had died within the previous 10 years. Results : A total of 13,741 questionnaires (24% response rate) containing information on 15,881 deaths were included in the analysis. Breed-specific response rates ranged from 64·7 to 4·5%. The median age at death was 11 years and 3 months (minimum=2 months, maximum=23 years and 5 months) and it varied by breed. The most common causes of death were cancer (n=4282, 27%), “old age” (n=2830, 18%) and cardiac conditions (n=1770, 11%). Clinical Significance : This survey shows breed differences in lifespan and causes of death, and the results support previous evidence that smaller breeds tend to have longer lifespan compared with larger breeds. Although many of the breeds in the study may not be representative of the general pedigree dog population in the UK, the results do contribute to the limited information currently available.     

Mortality in over 350,000 insured Swedish dogs from 1995-2000: I. Breed-, gender-, age- and cause-specific rates

This study presents data on over 350,000 insured Swedish dogs up to 10 years of age contributing to over one million dog-years at risk (DYAR) during 1995-2000. A total of 43,172 dogs died or were euthanised and of these 72% had a claim with a diagnosis for the cause of death. The overall total mortality was 393 deaths per 10,000 DYAR. Mortality rates are calculated for the 10 most common breeds, 10 breeds with high mortality and a group including all other breeds, crudely and for general causes of death. Proportional mortality is presented for several classifications. Five general causes accounted for 62% of the deaths with a diagnosis (i.e. tumour (18%), trauma (17%), locomotor (13%), heart (8%) and neurological (6%)). Mortality rates for the five most common diagnoses within the general causes of death are presented. These detailed statistics on mortality can be used in breed-specific strategies as well as for general health promotion programs. Further details on survival and relative risk by breed and age are presented in the companion paper (Egenvall et al. 2005).