Hip Dysplasia
Hip dysplasia is a devistating developmental orthopedic disease which primarily affects larger breeds of dogs. It is a multifactoral disease meaning it has both genetic and environmental compenents. The genetics are not simple dominant/recessive type genes, but instead depend on a variety of genes which each express some small part of the complicated coxofemoral (ball and socket) hip joint. Issues such as how flat or spherical the femoral head (ball) is and the depth of the acetabulum (socket) in the pelvis play a role in the stability of this joint. The better constructed the joint the more stable and the better the wear and tear through years of use. The more slopily arranged the joint, the more laxity or movement between the joint surfaces and the more pain and degenerative disease that will occur. Dysplastic dogs can sometimes be identified at less than 4 months old using x-rays, although the final development is not finished until much older. This is why hips can not be certified by the Orthopedic Foundation for Animals (OFA) until 24 months old and the final development is complete.
While not an OFA positioned film, due to the lack of perfect pelvic positioning, this presurgical film demonstrates a hip joint that is subluxated or mosty out of socket, with a shallow acetabulum or socket and a trangularly shaped femoral head with poor femoral neck angulation (the femoral head is only slightly angled off the axis of the femur rather than jutting more to the side. This is severe hip dysplasia.
The second factor in the development of hip dysplasia is environmental in nature. This includes factors such as obesity as a puppy and the plane of nutrition. Animals encouraged to grow too quickly may reach their ultimate weight sooner, but may also enhance any weakness in their genetic make-up as far as joint conformation is concerned. This has prompted an awareness in nutrition for larger breeds and the creation of "Large Breed" puppy foods from many manufacturers. Some feel that too early an introduction to traumatic performance, especially jumping, may also predispose a puppy to eventual joint disease. Thus, a dog with marginal genetics who is raised with excellent nutrition that encourages slow growth and is kept trim with patience as far as training may end up with good anatomy and a healthier future than a puppy who is fed poorly, kept overweight, or is worked prematurely. Again, hip dysplasia is multifactoral in nature.
Hip dysplasia is not simply a "you have it or you don't" type of health problem. It is a gradation in quality of hip joint that then will have a spectrum of possible effects on the dog itself. Some dogs with horrible appearing hip joints are still chasing tennis balls and competing while other dogs with what may appear marginal dysplastic changes on an X-ray may be crippled. This does not mean that radiographic diagnosis is worthless, but it means we have to use more than just images of the joints in interpreting the animal's well being. We also should be striving to not just have all breeding animals OFA certified before breeding, but to go further in the name of controlling this problem. We should be suggesting screening x-rays for all puppies at 6 months of age (when they are spayed or neutered if they are) or at any suggestive evidence of problems (bunny hopping gait or difficulty getting up from a sit or down position). We should be encouraging communications with people who buy puppies so that if they have a problem, we don't offer excuses, but thanks for alerting us of a problem with our lines.
It is possible for a breeding pair of dogs with "good" hips to produce a puppy with fair or even dysplastic ones. Remember, part of the anatomical outcome depends on environmental issues. The X-rays that the OFA uses to certify hips only reflect the total combination of genetics and environmental factors. Thus, a dog with fair or possibly even mildly dysplastic genetics may have deceivingly good x-rays if nutrition and other factors are all good. Also, each parent supplies half the genetic material of the offspring. Thus if a dog has good hips, but has some problematic genes, and these genes are the ones that get passed on to the puppy, through random distribution, the offspring may have the disadvantage of those poor genes. Combined with a random sample from the other parent, we may see offspring with a range of hip quality. In these cases, we need to be attentive to the breeding history as we continue to make breeding decisions. It may not be necessary to retire OFA "Good" dogs who produce a single dysplastic puppy. On the other hand, for every dysplastic puppy found, how many others will simply have hip problems down the road that are more prominent because of the poor anatomy that went unnoticed as a young dog. Thus, at a minimum, it would be wise to avoid that particular pairing and possibly choose to test mate these dogs with other OFA "Good" or preferably "Excellent" partners.
What is the future of a dysplastic dog? Because of the broad spectrum of anatomical severity and resulting phenotypic display (what you'll see clinically as far as disability) it is hard to predict. Some animals may not show problems until middle age or older. Typical symptoms are difficulty getting up, difficulty climbing stairs, getting on furniture, or into the car/truck. A "bunny hopping" gait while running may also be noticed. X-rays will show degenerative changes of the hips, and possibly signs of dysplasia that simply were never looked for in the young dog since there were no symptoms. At this stage, medical therapy with antiinflammatories and the addition of nutriceuticals (joint supplements) are the typical approach. Total Hip Replacement is a surgical "cure" that is available at some veterinary specialists. This is often a fairly expensive surgery with it's own set of possible complications, but often repair of even one of the two hip joints can result in a amazing improvement of mobility. A "salvage" procedure would be an FHO (Femoral Head Osteotomy). This is the surgical removal of the femoral head, which eliminates the pain of an arthritic, degenerative hip joint. The cost is much less than that of a Total Hip Replacement, but the patient is left with no actual joint between the femur and the pelvis. Instead, a pseudoarthrosis or false joint will form. Depending on the dog, it's weight, activity level, etc... this can result in a spectrum of outcomes ranging from nearly normal movement to a marked gait deficit where the false joint does not carry weight properly. Also, this tends to only be acceptible on one side, so the worse joint is obviously chosen. This leaves a false joint and the remaining dysplastic joint. The animal's tolerance to using the remaining joint, which now is burdened with even more of the weight load, will ultimately be a deciding factor in the surgery.
In young dogs, particularly those diagnosed at less than one year, and ideally diagnosed at less than 6 months, a TPO (Triple Pelvic Osteotomy) surgery may be performed which changes the angle of contact between the ball and the socket, improving the long term usefullness of the joint. Typically both joints are corrected, one after the other has healed. The response is usually dramatic and a good long term prognosis is often given. Obviously cases diagnosed this early are often more severe, so one can not be assured of a good outcome, despite the skill of the surgeon, but if left untreated, these pups who are already showing hind end weakness and pain are doomed to suffering. If surgery is not an option, then medical therapy can still be attempted, but this likely only puts off the inevitable.
Cutting of the pelvic bones in 3 places to free up the acetabulum with special surgical saw. A special TPO bone plate fixing the piece at a new angle
The final product with a new hope!
A TPO or Triple Pelvic Osteotomy involves cuts in ilium, ischium, and pubis bones of the pelvis, allowing the acetabulum or socket to be rotated into a new position so that the bony shelf covers the femoral head or ball much better. Special TPO bone plates with different angles can be used depending on the degree of problem. The result should be a much more stable joint allowing for an improved future.
To learn more about Hip Dysplasia and getting your dog checked or certified by the experts, please visit the Orthopedic Foundation for Animals website.