Hip dysplasia, or the congenital malformation of the hip joint, continues to be a serious problem in almost every breed. Because of hip dysplasia and the subsequent chronic pain and disability, many dog owners find that they cannot use their dogs for their intended purpose, such as hunting, agility, search and rescue or as a running partner. Moreover, treating hip dysplasia is costly, whether it entails surgery, long term pain medications, nutraceutical supplements, injectable joint protecting medications, acupuncture or physical rehabilitation. The most severe cases will likely require all of the above, or a combination of these treatments. In addition to the cost of long term treatment, one might also count the cost of purchasing, feeding and training a dog, only to find out that he is not able to perform as planned. The frustration and disappointment from the owner for dealing with this chronic and debilitating condition is an additional concern.
The PennHIP (Pennsylvania Hip Improvement Program) evaluation was developed in 1993 at Pennsylvania State University. The purpose of the PennHIP evaluation is to accurately detect hip problems as early as possible and to predict if a dog is genetically predisposed to develop hip arthritis. PennHIP evaluations can be done as early at 16 weeks of age. In comparison, for OFA (Orthopedic Foundation for Animals) evaluations, dogs have to be at least 2 years old for both the evaluation and registration. OFA evaluations for hips have been the standard of care since 1966 and are, unfortunately, still the only hip scoring method accepted by the AKC (American Kennel Club). The problems with the OFA evaluation for hips is evident in the fact that the incidence of hip dysplasia has not declined significantly since its use nearly 50 years ago. Studies have shown the apparent lack of correlation between OFA evaluations in breeding stock and the predilection for developing hip dysplasia in the offspring. In PennHIP evaluations a DI (Distraction Index) is calculated, dependent on the laxity of the hip joint. The dog is then compared to dogs of the same breed and ranked accordingly. A dog that has a DI of 0.3 or less is not expected to develop hip dysplasia unless there is some trauma: A dog with a DI of 0.7 or greater is almost guaranteed to develop hip dysplasia in his or her lifetime. Although PennHIP does not make recommendations as to which dog should be included or excluded from a breeding program, it stands to reason that a dog that ranks below the 50th percentile when compared to other dogs of his breed or has a DI that clearly predicts hip dysplasia, should most likely not be bred.
There are several advantages to having the hips evaluated at the early age that PennHIP evaluation allows. Because a bitch may be excluded from a breeding program due to a high DI, she can be spayed before she has her first heat cycle, thus significantly reducing her risk of mammary cancer. A bitch that is spayed before her first heat cycle has the same risk of developing mammary cancer as a male dog, which is 0.05%. This early screening is not possible with OFA evaluations, as these evaluations are done at 2 years of age. By that time the bitch has had already two heat cycles and thus her statistical lifetime risk of developing mammary cancer is 24%, as opposed to the bitch that was spayed before her first heat cycle. Some puppies that are at high risk for developing arthritis in the hip joints will benefit from supplements that protect the joints, such as Omega fatty acids (fish or safflower oil) and Glucosamine. Finally in cases where the DI is close to 0.7 or above, a Juvenile Pelvic Symphysiodesis (JPS) procedure could be done. The Journal of the American College of Veterinary Surgeons published a paper in 2000 that showed 25% prevalence of degenerative joint disease (DJD) or hip joint arthritis in puppies that had a JPS done by the time the dogs were two years old. By comparison, dogs that did not have a JPS done had an 83% incidence rate of DJD. Certainly special efforts should be made to keep all dogs with a high DI lean and well muscled, which is absolutely the most important factor to minimize and delay hip dysplasia.
At Apex Animal Hospital we have seen dramatic decreases in hip dysplasia in some lines of hunting dogs, such as German Shorthaired Pointers, Wirehaired Pointing Griffons and Weimaraners, where breeding stock is routinely PennHIP evaluated. Some local Labrador retriever breeders are also starting to use PennHIP evaluations and are making good progress. We hope that more and more consumers will demand PennHIP evaluations from their breeders, before they purchase a puppy so that over time this terrible condition can be much reduced or even eliminated.
The first of the two graphs depicted below is based on a study done in 1993. It illustrates the high correlation between PennHIP evaluations and the incidence of hip dysplasia and hip arthritis. 142 dogs were PennHIP evaluated. Of the dogs with a DI of 0.3 or less, only one dog out of 67 dogs developed hip dysplasia. Of the 3 dogs with a DI of 0.7 or above, all dogs developed hip dysplasia. The second graph is based on a study published by The Journal of American Veterinary Medical Association (JAVMA) in 2010. That study compared OFA hip evaluations with “distraction x-rays”, also known as PennHIP evaluations. 52% of the dogs that were rated OFA “excellent” had a DI of > 0.3 and were thus at risk of developing hip dysplasia. The DI ranged in the “excellent” group from 0.14 to 0.61. Of the dogs that were rated OFA “good” 82% had a DI of > 0.3 with a DI range from 0.10 to 0.77. Of the dogs that were rated OFA “fair” a whopping 94% had a DI of > 0.3 with a range from 0.14 to 0.77! The study shows that when breeders are using OFA evaluations in determining which dog to include or exclude from a breeding program, many dogs that are predisposed to developing hip dysplasia will be bred. On the other hand, some animals with very tight hips that will never develop hip dysplasia and would actually be an asset to a breeding program may be excluded because they did not rank as high on their OFA evaluation.