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Canine hip dysplasia: new trends in diagnosis, treatment and prevention
Canine hip dysplasia affects millions of dogs each year. Abnormal development in the dysplastic hip causes damage to the articular cartilage of the joint, resulting in osteoarthritis, severe pain and eventually debilitation.
Ithaca, N.Y. — Canine hip dysplasia affects millions of dogs each year. Abnormal development in the dysplastic hip causes damage to the articular cartilage of the joint, resulting in osteoarthritis, severe pain, lameness, and eventually debilitation. Both genetic and environmental factors play a role in the clinical signs and phenotypic expression.
Rory Todhunter, BVSC, PhD, DACVS, a professor of surgery at Cornell University College of Veterinary Medicine, has spent more than 15 years researching canine hip dysplasia. He spoke with DVM Newsmagazine recently about the disease and the direction of his latest work.
DVM: Are certain dog breeds more prone to canine hip dysplasia? What are some factors that contribute to the development of this condition?
Todhunter: Hip dysplasia is a developmental malformation of the hip joint of any breed of dog, but the ones we usually think of as clinical problems are medium- to large-breed dogs. As reported by the Orthopedic Foundation for Animals (OFA), the incidence of the trait gets as high as 70 to 80 percent in some breeds—most commonly bulldogs—but also Newfoundlands, Saint Bernards, Labrador retrievers, and golden retrievers. At least 85 to 90 percent of the time the conditions involves both hips, but usually one is worse than the other.
Hip dysplasia or any other developmental orthopedic trait has an underlying genetic cause, but there are nongenetic contributions. Nestlé Purina studies that examined the effect of growth rate on the severity of developmental orthopedic traits implied that dogs with a restricted diet had less secondary arthritis, less severe hip dysplasia, and fewer problems in other joints than free choice-fed animals.
DVM: How is canine hip dysplasia best diagnosed? Describe the limitations of current radiographic techniques or other diagnostic tools.
Todhunter: The traditional imaging position, the extended hip or OFA view, is the one most veterinarians are familiar with. You can have dogs that look good in that position, but actually have hip joint laxity, instability, and dysplasia. The University of Pennsylvania Hip Improvement Program (PennHIP) uses the distraction view to measure the maximum laxity in the hip joint. Then, the extended hip view is used to determine whether the dog is dysplastic and if it has secondary arthritis.
Dr. Rory Todhunter with a patient.
Generally speaking, I suggest veterinarians use the extended hip view combined with either the distraction index (DI), the dorsal lateral subluxation (DLS) method, or with physical palpation to make the diagnosis.
The traditional palpation method for young dogs would be the Ortolani maneuver, which is the same maneuver pediatricians use on human infants to determine if there's an instability in the hip. When performing the maneuver, feeling a click or a clunk means the hip is abnormal. But if you have a severely dysplastic hip and you don't have enough structure in the acetabulum, then you're not going to actually feel the click or the clunk. It can also mean that the hip may be out altogether or the dog is just not sufficiently relaxed.
DVM: Please discuss the treatment options for canine hip dysplasia, both surgical and nonsurgical.
Todhunter: If the patient is having clinical signs and pain, nonsteroidal anti-inflammatory drugs (NSAIDs) will decrease the pain and the inflammation, but you want to use them sparingly because of the potential side effects.
You can also use nutraceuticals, some designated specifically for veterinary use. One, for instance, is a combination of glucosamine, chondroitin sulfate, and manganese ascorbate, but there are dozens that you can get off the shelf in health stores. They won't give immediate relief, but over the long term, they may decrease the amount of NSAID needed. There's some evidence that nutraceuticals have anti-inflammatory properties and may help in cartilage regeneration. But you're not going to make an abnormal joint normal; at best, you may help it.
Another way to modify expression of canine hip dysplasia is exercise modification and physical therapy. There are many people now trained in ways of modifying the physical activity of dogs to help them function better. It goes along with diet and the most important treatment of all-body weight reduction to an ideal body weight.
A surgical option for dogs less than 4 months old is a juvenile pubic symphysiodesis, which fuses the bottom of the pelvis and stops it from growing. The top part of the pelvis grows and, hopefully, eventually captures the femoral head. But that takes time.
When the dog is a little older, say 4 to 6 months, you can do a triple pelvic osteotomy, which physically repositions the cup over the femoral head. You're not going to have a perfect hip, and the dog will still get some degree of arthritis down the road, but the idea is to make it better than it was before.
Surgery at maturity would be either a total hip replacement or an excision arthroplasty, where you remove the femoral head and neck, and a false joint forms. This works very well in small- to medium-size dogs. It also gets rid of pain in larger dogs, but the physical and mechanical function is not as good as a total hip replacement. Total hip replacement works very well if done by people who are good at it. Like all types of total joint replacements, the big issues are infection, fractures, loosening, luxations, and nerve damage, some of which can occur immediately after the surgery or at some point down the road just like they do in human joint replacements.
DVM: Please discuss your own research, the dorsal lateral subluxation imaging test and the genetic mapping project on dogs with hip dysplasia. How do you see your work impacting the care and treatment of affected animals in the future?
Todhunter: We developed an imaging method where the dogs are positioned in sternal recumbancy—on their chest and kneeling on their stifles—mimicing what you would do in the initial phases of the Ortolani test. We take a dorsoventral image, in what we believe to be a more functionally relevant hip-imaging position.
What we've shown is that this type of imaging is more accurate in determining whether the hips will eventually become arthritic. The sensitivity is around 80 to 85 percent, and if you add a second imaging position like the OFA view and measure the Norberg angle, you can improve the accuracy of the arthritis prediction.
At the moment we are undertaking genome-wide genetic marker screening tests on populations of dogs to identify which genes contribute to the affected phenotype. Eventually we want to get enough genetic markers and enough animals that have been phenotyped so we can narrow our investigation to the affected region and start to look at candidate genes.
I've been pushing the idea to combine genetic information contained within a dog's pedigree with the phenotypes and the hip confirmation information (together called a breeding value) and provide it to breeders or potential purchasers of puppies. The pedigree information improves the estimate of the dog's genotype, and when you combine that with the radiographic information, you get a much better idea of the likelihood of a good or bad outcome.
DVM: What would you like general practitioners to know about this disease?
Todhunter: Prevention is better than cure. Once established, you can't cure the hip problem except by removing it. So let's focus on the available tools to try to breed dogs with better hip conformation. In fairly short order we'll be able to supply breeding values that will provide owners with even better tools for breeding and purchasing selection.
Once you have a puppy, you need to restrict its growth and check it when it's being vaccinated. At maturity, screen it for hip quality using two of the radiographic assessment tools easily available.
Eventually, veterinarians should be on the lookout for genetic marker-assisted selection, which will use molecular genetic tools to identify dogs that are susceptible and resistant to hip dysplasia.
I predict that when the public knows these tools are available, they're going to demand them, so veterinarians have to be ready to answer questions, provide tests, and then know how to advise breeders and owners appropriately. We're just at the uptick of this slope, and in the next five to 10 years you're going to see many of these developmental problems starting to be resolved and the underlying genetics understood.
Wetzel is a free-lance writer in Cleveland, Ohio. For more information, visit the Orthopedic Foundation for Animals website, www.offa.org.