FAULTY JOINT DEVELOPMENT IN DOGS
Breeders and lovers of large breed dogs know all too well the heartache of canine hip and elbow dysplasia. Dog owners see patellar subluxations, cruciate tears and osteochondritis dissecans (OCD) in young dogs at an alarming rate and they pay the price with expensive surgery, therapy and supplements.
Why are dogs suffering from these diseases at such a young age? Many breeders and vets are quick to say that it is due to bad genetics – so good breeders screen their dogs for these diseases by way of X Rays before breeding, to make sure the problems are not passed down to the offspring. Unfortunately, this method of screening hasn’t really changed the incidence of most of these diseases.
Hip ‘dysplasia’ was first diagnosed in dogs in 1935 and over the next twenty years the number of dogs presenting with this disease prompted the Swedish Kennel Club to become one of the first to develop a program to reduce the incidence of hip ‘dysplasia'. The breeds in which this was noticed were Labradors, Retrievers and German Shepherds; however, this may simply be because they were the most popular breeds at the time. It is now thought that proportionately these breeds are no more susceptible to hip problems than any other breed given the numbers of popularity.
It was believed at the time that if breeders took radiographs of their dogs and only bred those dogs that did not show evidence of hip ‘dysplasia’, they could eliminate it. However, after ten years of selective breeding of German Shepherds, the incidence of moderate and severe cases of hip ‘dysplasia’ had not changed. Dogs that did not show radiographic evidence of hip 'dysplasia’ were still producing puppies with the disease. In one study, over two thirds of dysplastic puppies were from normal parents.
This led researchers to conclude that hip 'dysplasia' was a polygenic disease (residing in more than one gene), meaning that the severity of the disease could be influenced by environmental factors such as diet and lifestyle.
Over fifty years later, despite increased testing rates, the incidence of hip 'dysplasia' is not going down in most breeds. In fact, smaller breeds are now also showing an increased susceptibility to this disease which historically was limited to larger breeds of dogs
WHAT IS DYSPLASIA
The term ‘dysplasia’ sends shudders through any breeder, but it is important to understand that the word ‘dysplasia’ is NOT a pathological diagnosis. The word is derived from the Greek dys = bad and plasia = formation, and is a term frequently used to describe the general appearance of an abnormal joint (or any other tissue) but it is NOT specific to any single diagnosis. For example, an x-ray taken at skeletal maturity may show changes from conditions such as healed trauma, growth plate injury, Septic Arthritis and Perthes disease which can all look similar to possibly genetic disorders. These conditions are acquired after birth and the genetics are NOT proven, despite decades of research. The simple fact is that there has NOT been a link established between hip and elbow problems in humans, other than in dwarfism, let alone dogs. It is worth considering that dwarf breeds of dogs are generally not hip scored in many countries for exactly this reason.
‘Dysplasia’ is a term frequently used to describe the general appearance of an abnormal hip on x-ray.
The ‘Dysplasia’ score given from x-rays does not include a diagnosis
Perthes is probably not genetic…in humans found to be more prevalent the further away from the equator
A great deal of published ‘research’ material has been taken from X-Rays for ‘scoring’, not from diagnosis. For example, a diagnostic image will usually be acquired in two planes, not one (as required for hip scoring) and will not be distorted by traction or leverage designed to demonstrate ‘laxity’. Even the laxity images are difficult to compare as the amount or direction of traction is not specific for the breed, gender or size of the dog, therefore making scientific validation impossible.
With more than 50 years of ‘scoring’ there has been no statistically significant reduction of ‘dysplasia’ in any breed studied either by imaging or, more recently, gene studies. The overwhelming evidence is that the current method of ‘scoring’ is not a valid health screening test. If it were, it would be repeatable, producing the same score from the same film time after time, whoever the observer and in different countries. The issue is that there is so much variability between countries, vets, and opinions when scoring X rays that it is impossible for any breeder to have confidence when deciding which dogs to include or exclude from their breeding program.
Furthermore, after over 15 generations of breeding surely the condition would have significantly reduced. In one well respected publication it states that is has in fact increased in 14 breeds and remains unchanged in 17; where scores have reduced it has on been by one or two points in the majority, so in view of pre-selection, is not of any statistical significance. (3)
The ‘Dysplasia’ score given from x-rays does NOT include a diagnosis of genetic disorder, but despite this the consequences of a bad score frequently lead to complaints against the breeder which may be unjustified. The traditional scoring method takes account of many factors without being breed specific. One of these factors scored is laxity; breeders understand this varies greatly between breeds and gender and is frequently a reason why certain dogs are able to do the jobs for which they were first bred. We take for granted the skin laxity in some breeds such as Bloodhounds and Mastiffs.
In human studies, joint laxity following trauma is highly correlated with early onset of osteoarthritis. Non -traumatic laxity has NOT been correlated with premature arthritis except in very rare conditions.
It is widely known that research for the benefit of humans has involved dogs; Norberg, a radiologist who worked at the Karolinska Institute, Stockholm and famous for developing the Norberg angle for diagnosis and treatment of faulty hip development in babies, used his expert knowledge of human joint disorders, stating in his original published work with co-workers on hip ‘dysplasia’ in dogs from the early 1960s...
‘However, the Basic features are similar and for this reason one has the right to assume that the disease is basically the same in the two species.’ (1)
Sadly, this opinion has rarely been applied for the benefit of our dogs. From 1957 to 2015 there was still a failure to learn from Norberg and his colleagues who believed that: ‘environmental factors are responsible for about 50 per cent of the variation of the severity of hip dysplasia. (2)
Possibly of even greater importance is the advice 20 years ago of the Late Prof. George A. Padgett in his Textbook “Control of Canine Genetic Diseases” (Howell Book House 1998) (5) where he lists many of the acquired disorders that must be excluded before considering a possibly genetic disorder causing hip ‘dysplasia’.
The only in vivo internal joint investigations in the 1960s were X-Rays, Hendrickson, Norberg et al did not have the benefits of the extra scientific evidence that today can be obtained by CT, MRI and Ultrasound Scanning which are used for the benefit of humans; this does not yet appear to have been successfully incorporated into veterinary text books to differentiate between all the potential non-genetic reasons for faulty joint development in dogs. It is therefore sad that X-Rays are still being taken under anaesthetic, with all the documented risks, to make a ‘score’ that are not suitable for clinical diagnosis. These x ray films could not indicate if the abnormality was more probably genetic in origin than not. Furthermore, veterinarians all over the world have been educated to believe that ‘dysplasia’ of hips is genetic in origin and, even more disturbingly that elbow dysplasia was similarly genetic when there is, in fact, evidence to the contrary (4).
Indeed, one Elbow scoring system uses a single lateral view of the elbow joint to illustrate the Anconeus Process, suggesting that this is the origin of dysplasia, while a standard and much respected Radiology text book (6)shows that there is NO separate growth plate in the Anconeus and that all the evidence points to a fracture that has failed to unite properly or at all.
By scoring rather than diagnosing there is therefore a huge amount of untreated disability in young dogs that could have led to a high or normal level of function in the dog’s advancing years had correct treatment been given. Would this be acceptable for humans?
It is important to recognise the wide-reaching implications of a scoring system based on a phenotype image coupled with pre-selection (pre-selection because generally not all puppies born in any one litter are scored). We understand that siblings may and do differ in their genetic make-up. One may carry a recessive gene while another does not.
A paper published, In The veterinary Journal In Practice. By Ruth Dennis. 2012 clearly demonstrates that the existing scoring method, when the figures are viewed closely, actually show an increase in the incidence of ‘dysplasia’ across many breeds.
So the questions remain....if the scoring method is designed to improve ‘canine hip dysplasia’ why after 50 plus years and up to 20 generations of dogs have we not seen a statistically significant improvement across all breeds?After all, it’s not as if it is a new study. Why are there such discrepancies? Why has it never been validated?
In the very near future explanations of why a joint has developed badly will emerge. Some are likely to have a genetic origin, be it through gene mutations or SNIP (single nucleotide pleomorphisms) aberrations. But at least this will be observed against a background of confirmed normality in the first few weeks of life without pre-selection bias. We intend to provide information that is scientifically validated, that can be relied upon, be repeatable and be robust around the globe.
THE PUPSCAN PROJECT
PUPscan have established that there are significant differences in the development of puppy hips between breeds and even between the genders within each breed.
The Pupscan project began 3 years ago, with the aim of finding the processes that lead to hip and elbow ‘Dysplasia’ and is supported by a team of vets, breeders, geneticists and human medical professionals dedicated to the health and wellbeing of dogs. Pupscan is a ‘not-for-profit’ research organisation.
Pupscan uses the most modern diagnostic Ultrasound technology to separate joint disorders at birth, from those that are certainly acquired later in life through environmental and nutritional factors. PUPscan have established that there are significant differences in the development of puppy hips between breeds and even between the genders within each breed. This is the basis for a guidance that is being produced by breed experts on the best way to care for a new puppy.
The benefit to both the dog and breeder is that diagnostic images, incorporating new precise measurements which are being developed breed by breed, can be taken of hips and elbows from 14 days to 16 weeks of age, confirming normal development. The breeder therefore has as much information as possible about the joint development of each puppy within a litter and is in a position to make an informed decision regarding future breeding lines.
Ultrasound diagnostics supports both the breeder and the puppy and helps to defend against a future bad score that may result in allegations or claims of selling a ‘dysplastic’ puppy.
The PUPscan Project, working together with University College Dublin and supported by the Irish Kennel Club, is generating scientifically based data to highlight the importance of breed and gender specifics, husbandry, nutrition, exercise, and the conditions in which each pup was born.
As with humans, the intra-uterine environment and birth process often give rise to conditions that are diagnosed soon after birth that may be entirely unrelated to the genetics of the puppy. An example is when the amniotic sac either leaked during pregnancy or had too little fluid in which the embryo could move, resulting in abnormal (arthrogrypotic) joints. There is no evidence to suggest that puppies are immune for the same processes, why in large litters are puppies any different? we are all familiar with the term ‘runt of the litter’…is this runt sometimes the one that had too little room?
Single Pregnancy with lots of space Multiple Pregnancy with limited space
If a dysplastic puppy is found (so far our figures show one in a thousand of 61 breeds scanned) we can then carry out well targeted genetic screening with a far greater chance of finding the gene(s) involved.
The Pupscan team will work with breed clubs and individuals to produce breed specific data giving clear guidance and responsibilities for new puppy owners. This information will reinforce the puppy’s new owners’ duties of care and responsibilities to their puppy with clear evidence based on holistic guidance to include advice about exercise and activity, breed specific health issues and nutritional advice.
Pupscan trained Vets will be best placed to support not only the breeder but also the new puppy owner. They will have the training and equipment not only to scan for pregnancy but also carry out hip, elbow and knee scans that can be checked against the Pupscan database for breed and gender specific normal values.
For the expert breeder the new knowledge that the whole litter has been scanned and shown to be developing within it range of normal will give reassurance of health for future litters using the same parents or others that have been confirmed to have produced normal litters in the past. Within a very few years this new database, based on microchip and/or DNA identification, has the potential to register results from across the globe.
At first glance there seems to be no justification for NOT scanning. Every breeder and owner will benefit. If a dysplastic puppy is found (so far our figures show one in a thousand from over 3,500 hips scanned over 62 breeds)we can then carry out well targeted genetic screening with a far greater chance of finding the gene(s) involved.
THE SCANNING PROCEDURE
From 3 – 16 weeks of age depending on breed when the hip and elbow is predominately cartilage a diagnostic image is acquired by Ultrasound, a non-invasive imaging technique that does not require any hair removal or sedation. The scan is performed in real time, there is no ionising radiation and therefore there is no risk to ovaries or testes.
Ultrasound imaging allows internal body structures to be seen by recording echoes or reflection of ultrasonic waves. No anaesthetic or sedation is needed. The image is taken while the puppy is in a natural position. Both hips or elbows can be imaged in less than 15 minutes.
Pupscan are working with a global supplier of Diagnostic Ultrasound equipment supported by specially developed software. This will ensure diagnostic quality images, supporting the scanning technicians in working to a satisfactory diagnostic standard. The Diagnostic Technician will scan the hip/elbow joints to produce quality images required for the Pupscan specialists to analyse.
Once images, measurements and all other data is collated against a puppy and only when all data is signed off will a certificate be produced to confirm normal development. These Certificates can be passed to the new owner at the point of sale or at the breeder’s discretion. This will form part of the Puppy Contract confirming that the hip (or other relevant joint) is developing normally for age, gender and breed.
Because there will be a permanent record by Microchip and / or DNA identification from birth and within the first few weeks of life any disorders arising in a scanned/x-rayed joint later in life can be correlated against the early images so that any disorder or disease progression can be properly assessed and investigated. This will separate the acquired condition from all the other processes that can lead to the appearance of ‘Dysplasia’.
As larger and larger numbers of litters are entered into the database we expect that new disease processes will be clarified, especially on a breed by breed basis, so that early detection can lead to early treatment. Prompt removal from the breeding gene pool will therefore be based on sound scientific evidence rather than the current system that has failed to resolve the problem of faulty joint development in over 50 years.
X RAY REFERRAL SERVICE
This service has been developed at the request of breeders and owners who wish to know if their dog has a disorder of joint development that is predominantly genetic or acquired. The service is designed to allow breeders to make their own informed decision regarding including or excluding a dog from their breeding lines.
Acquired conditions may be responsible for poor hip or elbow scores, these processes MUST be considered before diagnosing a genetic abnormality.
The referral panel, consisting of both veterinary and human orthopaedic specialists working together, will review and report on submitted x rays. They will work with the breeder/owner and their vet to assist in any decision that may be required for the benefit of the dog.
A Comparative Review B. HENDRICSON, * I. NORGERG AND S.-E. OLSSON. Royal Veterinary College, Stockholm, Sweden. 1966
HENDRICSON, * I. NORBERG AND S.-E.OLSSON.Royal Veterinary College, Stockholm, Sweden.
Ruth Dennis. Interpretation and use of BVA/KC hip scores in dogs
Hou Y, Wang. Etal P L oS one 2013 October 4; 8 (10) Monitoring hip and elbow dysplasia achieved modest genetic improvement of 74 dog breeds over 40 years in USA.
George A. Padgett in his Textbook “Control of Canine Genetic Diseases” (Howell Book House 1998)
Coulson, An Atlas of Interpretation Radiographic Anatomy of the Dog and Cat. .