The aim of hip scoring is to have an idea of what our dogs have in store for them as they get older and also to try and improve the hips of all of the generations of our puppies to come.
Why do we need to hip score?
Hips are a ball and socket joint. If the ball is too loose and doesn’t fit the socket properly, it causes instability in the joint. Instability can lead to pain in the short term and arthritis in the long term which reduces function as well as causing pain that requires years of ongoing medication for relief.
Hip arthritis is one of the most common debilitating conditions in Chihuahuas and Poms as they age. In fact, a rather alarming study published in the Journal of Veterinary Medicine in 2017, The Demographics of Canine Hip Dysplasia in the United States and Canada, study by Dr Randall Loder, from the Department of Orthopaedic Surgery, Indiana University School of Medicine and James Whitcomb Riley Children’s Hospital, Indianapolis, and Dr Rory J Todhunter from the Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, states that up to 70% of the Toy Group dogs they surveyed in the USA and Canada, suffered from bilateral hip dysplasia. The only group that was worse than the Toys was the Terrier Group.
Hip scoring not only tells us how stable a dog’s hips are, it also tells us how likely it is a particular dog will develop arthritis as it gets older, as well as revealing any signs of Legg-Calve Perthes Disease.
Legg-Calve Perthes Disease is a painful condition where the blood supply to the head of the femur is interrupted. The femoral head then necroses (loses blood supply), which weakens the bone and can lead to multiple fractures. If the bone is resorbed, it can cause a complete collapse of the femoral head. The condition can only be treated by expensive femoral head excision surgery and pain relief. The Legg-Calve Perthes test is optional under the Dogs NZ Accredited Breeders scheme, not compulsory, like hearts, eyes and patellas, so few, if any breeders, bother to go to the expense of having the test done.
Fortunately, we have no dogs in our lines who suffer from this affliction so far, but as we’ve mentioned before, no other NZ Chihuahua or Pom breeder keeps the comprehensive, generation-spanning health records we have started to amass, so it’s nigh impossible to discover if it’s lurking unseen in our lines. We simply won’t know about it unless it unexpectedly rears its ugly (femoral) head at some point in the future.
As the US study demonstrates, canine hip dysplasia (CHD) is the main reason for hip scoring, however, and it’s highly heritable so we know dogs with hip problems are more likely to produce offspring that also have hip problems.
We are also particularly interested to discover if there is any correlation between hip issues and luxating patellas. The latter is disturbingly common in small breeds, particularly Chihuahuas and Poms, and while we screen diligently for luxating patellas, they are a “multi-factorial” condition – that is, like cryptorchidism, it takes more than just breeding from unaffected parent to eliminate it, as two clear parents can randomly produce affected offspring.
Remember the old song Dry Bones? “The leg bone’s connected to the knee bone, the knee bone’s connected to the thigh bone, the thigh bone’s connected to the hip bone…” (If you’re old enough, that song is stuck in your head now… you’re welcome)
There is more than a grain of truth in that fabulous old gospel song. We want to start monitoring this connection in our dogs, as it’s possible there is a correlation breeders are not aware of, simply because they screen “dem knee bones” but pay little or no attention to “dem hip bones”.
What’s involved in hip scoring?
Regardless of the method used, x-rays under sedation or general anaesthetic are required. There are two main methods of hip scoring available in NZ:
This scoring method is based on expert scoring of 9 different qualities of each hip joint – a score is generated for each joint (left and right). The x-rays are taken at or after 1 year of age and assessed by a panel of experts in Australia.
This stands for Pennsylvania Hip Improvement Program – it was designed at the University of Pennsylvania in the USA. It is the gold standard for hip scoring.
This system gives a more accurate idea of a dog’s long-term hip health because it measures true laxity and the scoring can be performed from 16 weeks of age which is useful when considering if a dog is a sound breeding prospect.
PennHIP is also much more expensive as it requires veterinary accreditation to take the x-rays under general anaesthetic but the good news is that we have two accredited vets at the Tram Road Animal Care Services clinic where Tracey practices - Tracey and Dr Meredith Barth - which means we’re able to submit x-rays for scoring to the University of Pennsylvania.
The bad news for Chihuahuas and Poms, sadly, is it is exceedingly difficult to score them using PennHIP because of their size. Despite TRACS owning the smallest distractors available for PennHIP scoring, Chihuahuas and Pomeranians are simply too small to be placed in the correct position, even under general anaesthetic. (Don’t laugh, but in the case of the boys, their balls get in the way!)
So, we have started our own scoring program, which will now become a standard test on all our breeding dogs in the future, using the CHEDS assessment out of Australia. We’ll still get valuable information about our dogs’ hips, but we’ll have to wait until the dogs are a year old, before we can assess them.
Over the new year break, all our Chihuahua stud boys have been x-rayed and the images submitted for assessment to CHEDS. Once we have been able to assess more than 10 dogs, we’ll be able to get a breed average score, which is no easy thing to find for Chihuahuas, because few other breeders in the world go to the effort or expense of hip scoring their breeding dogs. The latest stats out of the UK in the 2020 Hip Dysplasia Scheme Breed Specific Statistics from the Kennel Club indicate that only 6 Chihuahuas and 2 Pomeranians were scored in the whole of the UK in 2020. To put that in perspective, despite extended COVID lockdowns in the UK, 48,037 German Shepherds were scored in the same period. Similar stats appear in Australia, where only 1 Chihuahua and 2 Poms have submitted results to CHEDS so far.
This, like most breeding assessments, is a long-term project. We’ll be contacting our local Kitaco owners with dogs over a year old to get their hips and patellas assessed too (probably when they come in for their dentals), so we can start to build up a picture of the hip health of our lines, discover if there is any sign of Legg Calve Perthes and look for any correlation to patella issues.
We’ll be adding this scoring to our Estimated Breeding Values (EBV) in which we are now tracking, hearts, patellas, hydrocephalus, cryptorchidism, temperament, jaw alignment and hips.
And in case you don't know the song Dry Bones, here’s the awesomely talented Delta Rhythm Boys with their original 1947 version. It’s worth reading the comments on the clip, too, about the shocking limits put on these guys during this TV appearance in the 1950s because some of their songs were deemed "unsuitable for white audiences". What awful creatures humans can be. Is it any wonder that here at Kitaco, we prefer dogs.
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