Canine Hip Dysplasia is the most common, heritable orthopedic problem seen in dogs.  It afflicts virtually all breeds of dogs but is especially problematic in large and giant breeds.  Clinically, the disease manifests itself in one of two ways:

A severe form that typically afflicts the younger animal and is usually characterized by marked pain and lameness,

A more chronic form with a gradual onset of clinical signs such as mild, intermittent pain, stiffness and restricted range of motion in the hips as the dog ages.

Since Hip Dysplasia can lead to debilitating problems in your pet, it is important for you to understand how hip dysplasia occurs (pathogenesis), how we can diagnose it and what you can do about it.

Canine Hip Dysplasia (CHD) literally means an abnormal development of the hips (dys = abnormal,  plasia = development).  CHD is a multifactorial developmental disease.  Dogs who are genetically coded for CHD will develop abnormally as they grow.   Environmental influences do not cause CHD, but they can have an impact on the severity of the disease.

Dogs who are genetically coded for good hips will develop good hips.  Dogs who are coded for bad hips may develop bad hips.  Environmental influences can be manipulated to alter the effects of genetics in dogs at risk.

The most important environmental influence is proper nutrition.  It is important for dogs who are susceptible to CHD to grow at a normal rate.  Many people feel that they should supplement their puppy's diet with extra protein and fat and calcium to help them grow.  This is actually detrimental to their health, as it can cause them to grow too quickly.  This rapid growth results in abnormal pressures on developing hips and can lead to a worsening of hip dysplasia.   There are a few companies today who have developed puppy food for large breed dogs which allows for a normal growth rate and we strongly recommend these diets in susceptible dogs.

Knowing the genetic background of a puppy and feeding diets that result in normal growth and development are the best steps you can take to reduce the risk of hip dysplasia.

No dogs at risk of hip dysplasia should be bred without having the hips evaluated in both dogs involved in breeding.  For further information on responsible breeding practices, please contact one of our hospitals.

There are two radiographic methods used to identify hip dysplasia.  The first, a subjective evaluation by the Orthopedic Foundation for Animals (OFA) has been the primary means of diagnosing hip dysplasia since 1966.  The second, an objective evaluation by the Pennsylvania Hip Improvement Project (PennHIP) is a newer, but very promising means of diagnosis.  The following discussion should help you decide which technique may be best for your pet.

The Orthopedic Foundation for Animals was developed in 1966 with the purpose of providing a standardized evaluation for hip dysplasia and to serve as a database for control of hip dysplasia through selective breeding. To date the OFA maintains the world's largest data base on hip conformation.

The OFA requires a single radiograph (x-ray) taken in a consistent manner with a number of specific technique requirements.  These radiographs are not required to be taken under anesthesia, but anesthesia is recommended in order to obtain the best view in a relaxed position.  The radiograph is then sent, along with a registration form, to the OFA, where it will be screened immediately for proper positioning techinique.  If the radiograph is not diagnostic, it is returned to the veterinarian.  Acceptable radiographs are then evaluated independently by 3 board certified veterinary radiologists and a consensus is derived.  The hips are evaluated for subluxation (looseness of hip joint), shallow acetabulum (the "socket" of the ball-and-socket hip joint) and signs of degenerative joint disease (arthritis).  This evaluation is most often completed within 3 weeks.

Once evaluated, the hips are reported to be in one of three categories: Normal, Borderline or Dysplastic.

Normal - Normal hips are further categorized as "Excellent", "Good", or "Fair".  All dogs over 24 months of age with normal hips will be assigned a breed registry number and will periodically be reported to the parent breed club and the AKC.

Borderline - OFA recommends a repeat study in 6-8 months.

Dysplastic - Dysplastic hips are further categorized as "Mild", "Moderate, or "Severe".  No OFA number is assigned.  Abnormal findings are only reported to the veterinarian and the owner of record.

A dog must be 24 months old to receive an OFA number.   However, preliminary studies can be done between 4 and 23 months of age.   These preliminary studies are reportedly 90%  accurate when compared to the follow-up studies done at 24 months of age.

Some female dogs show subluxation when radiographed around a heat cycle.  This subluxation will not be present when the dog is no longer in a heat cycle.  For this reason, the OFA recommends radiographs be performed no closer than 3-4 weeks before or after a heat cycle.

PennHIP is a scientific method to evaluate a dog for Hip Dysplasia.  In 1983, Dr. Gail Smith from the University of Pennsylvania School of Veterinary Medicine began to actively research and develop a new scientific method for the early diagnosis of Canine Hip Dysplasia.  This research resulted in a diagnostic method capable of estimating the susceptibility of CHD in dogs as young as sixteen weeks.

Three radiographs are typically taken in a PennHip evaluation and in order to obtain diagnostic radiographs, anesthesia is required.  In addition to the traditional "hip extended" radiograph, both a compression and distraction radiograph of the hips are taken.  This procedure allows the dog's "passive hip laxity" to be measured.  This is essentially a measurement of the looseness of the hips.  Research has shown that the degree of passive hip laxity is an important factor in determining susceptibility to development of degenerative joint disease (arthritis) later in life.

A PennHIP evaluation results in a confidential report to the owner indicating the dog's distraction index or DI.  The DI is a measure of passive hip laxity and is expressed as a number between 0 and 1, with 0 being very tight hips and 1 being very loose hips.  Multiple investigations have confirmed that dogs with tighter hips are less likely to develop joint disease than dogs with loose hips.   PennHIP data provides a profile for each individual breed of dog.  Over 165 breeds are represented in the PennHIP database.  PennHIP evaluations are currently recognized by the American Kennel Club and in the future, DI information will be included in the AKC's Information and Health Database.

The PennHIP method can be performed on dogs as young as sixteen weeks.

The most important features are the evaluation method and the age.  Let's take a closer look at each of these.

Evaluation method:  The OFA evaluation method is subjective.  This means that it is based on the opinions of the evaluators.  The conclusions reached on an individual radiograph could vary based on different opinions of the evaluator.  OFA radiographs are evaluated by board-certified veterinary radiologists, so these opinions are indeed "expert opinions" but there still exists room for error with any subjective method of evaluation.  For instance, what specific signs are required to be present or absent in order for hips to be considered "excellent" instead of "good"?   All normal hips receive an OFA certification number, but these normal hips can range from fair to excellent.  How does a person make good breeding recommendations based on these results?  We know that different breeds have different levels of hip quality, but OFA evaluation does not specifically say how a single dog compares to other dogs within its own breed.

The PennHIP method is objective.  This means that it is based on a specific factual measurement which is not influenced by the opinion of the person evaluating the hips.  The Distraction Index (DI) is a specific, measured evaluation.  However, in order to obtain consistency, only veterinarians specifically trained in the PennHIP technique can take the radiographs that are sent in for evaluation.  The results of the PennHIP evaluation are specific for each breed.   Instead of reporting a subjective analysis such as "good" or "fair", the PennHIP results are reported as a specific number (DI) which is ranked against all other dogs of the same breed which have been previously evaluated by PennHIP.  Therefore, you will receive a report telling you how loose your dog's hips are compared to all other dogs of the same breed.  This information is extremely valuable when trying to make breeding recommendations.

Age:  The age at which we evaluate hips is important for two reasons.  The earlier a breeder knows which dogs in a litter have good or bad hips, the sooner they can decide which dogs to keep as breeding stock and which to sell as companion animals.  In addition, there are solid medical reasons to spay female dogs prior to their first heat (see Spay/Neuter information) and this cannot be done if the dog cannot be certified until 24 months of age.  Preliminary studies can be done prior to 2 years but the predictability for breeding is not as good this early with OFA as it is with PennHIP.

We offer both the OFA and the PennHIP methods of evaluation for Canine Hip Dysplasia.  Dr. Schmidt is currently one of only a few veterinarians who have been certified for PennHIP evaluation.  We strongly recommend that intended breeding dogs of all breeds at risk for Hip Dysplasia (particularly medium to giant size breeds) be evaluated by one of these methods as a tool in selecting appropriate breeding animals.

While the OFA evaluation method has the advantage of history and public awareness, we believe that PennHIP evaluation gives more conclusive findings which can more directly be used to assist in breeding.  If you are not intending to breed your dog, but desire to know the status of your dog's hips, it is not necessary for you to proceed with either of these evaluation methods.  All of our doctors are capable of evaluating your dog's radiographs and if necessary, we can send the radiographs to a board-certified veterinarian for further evaluation.

This information is intended to introduce you to the methods used to diagnose Hip Dysplasia, but for specific recommendations about your pet and it's health, or specific breeding recommendations for your pet, please contact us for further information.
 
 

1All comments in the "OFA" section are taken directly from the pamphlet "Orthopedic Foundation for Animals".
2All comments int he "PennHIP section are taken directly from the PennHIP pamphlet produced by the Synbiotics Corporation, 3/98.
3This table reflects the combined recommendations/opinions of the respective organizations.

Related Links:
www.vet.upenn.edu/pennhip/