Canine Hip Dysplasia (CHD) is the most common, heritable orthopedic problem
seen in dogs. It affects virtually all breeds of dogs but is especially
problematic in large and giant breeds. Clinically, the disease manifests
itself in one of two ways: 1) a severe form that typically afflicts the
younger animal and is usually characterized by marked pain and lameness,
or 2) a more chronic form with more gradual onset of clinical signs such
as mild, intermittent pain, stiffness and restricted range of motion in
the hips as the dog ages. In many cases, the chronic form may be clinically
silent.
Breeders and veterinarians have long sought a reliable method to determine
the likelihood of a dog developing CHD and passing that genetic trait to
any offspring. It was generally recognized that the current diagnostic methods
of hip evaluation were associated with disappointing progress in reducing
the frequency of CHD. In 1983, Dr. Gail Smith, a veterinary orthopedic surgeon
and bioengineer 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. Research in his laboratory
resulted in a diagnostic method capable of estimating the susceptibility
for CHD in populations of dogs as young as sixteen weeks. The method has
shown distinct advantages over the standard CHD diagnostic method that evaluates
dogs at two years or older. The University of Pennsylvania Hip Improvement
Program (Penn HIP) was founded as an extension of Dr. Smith's laboratory
research. Below are answers to some commonly asked questions about the Penn
HIP method.
What exactly is Penn HIP?
Penn HIP is a scientific method to evaluate a dog for its susceptibility
to develop Hip Dysplasia. The radiographic procedure involves a special
positioning of the dog so that the dog's "passive hip laxity"
can be accurately measured. In simple terms, passive hip laxity refers to
the degree of looseness of the hip ball in the hip socket when the dog's
muscles are completely relaxed. Research has shown that the degree of passive
hip laxity is an important factor in determining susceptibility to develop
Degenerative Joint Disease (DJD) later in life. Radiographic evidence of
hip DJD, also known as osteoarthritis, is the universally accepted confirmation
of CHD. Penn HIP is being marketed by International Canine Genetics, Inc.
(ICG) of Malvem, PA.
How was Penn HIP developed?
The development of Penn HIP has involved multiple disciplines including
biomechanics, orthopedics, clinical medicine, radiology, epidemiology and
population genetics. The first phase of development involved sophisticated
biomechanical testing to determine the optimal patient position for measuring
hip laxity. By monitoring passive hip laxity in dogs as they matured, it
was discovered that hip laxity was the primary factor in the development
of the DJD characteristic of CHD. That is, the radiographic expression of
DJD was statistically significantly correlated with the degree of measured
passive hip laxity. In addition, the CHD prediction was shown to be acceptably
accurate in populations of puppies as young as sixteen weeks of age. Moreover,
the correlation between passive hip laxity and subsequent hip DJD was shown
to increase over the four-month figures when hips were evaluated at six
months and twelve months of age. In the same studies, it was shown that
there was no statistically significant correlation between laxity and DJD
when the standard hip extended view was used. In addition, no other method
used to evaluate for CHD has undergone similar rigorous testing through
controlled scientific studies to determine diagnostic accuracy.
How Does Penn HIP Differ from Evaluation Methods Which Use the Hip Extended
Position?
Penn HIP differs in some very fundamental and important ways. First, Penn
Hip was developed and tested following strict scientific protocol and the
results of these studies have been published (and continue to be) in peer-reviewed,
scientific journals. More than a decade of research and analysis has produced
a body of information in support of Penn HIP's effectiveness. As with all
diagnostic tests, Penn HIP's accuracy is not 100 percent, but in direct
comparisons it is far superior to any other available diagnostic method.
Second, passive hip laxity is objectively measured and the resulting Hip
Evaluation Report is not issued in a pass/fail framework. Penn HIP specifically
measures passive joint laxity and includes the quantitative measurement
in its report. Based on the degree of laxity, the individual dog is then
ranked relative to other members of the same breed. (Note: Breed specific
rankings are given when there are twenty or more evaluations. If there are
fewer than twenty evaluations - ranking is made to the general dog population.)
For example, a dog receiving a ranking in the 70th percentile means that
thirty percent of its breed members have hips that are tighter. This allows
breeders to easily identify those animals with tighter hips within each
breed. As shown in our studies, dogs with tighter hips are less likely to
develop CHD and pass that genetic tendency on to future generations. Third,
because Penn HIP is measuring maximal passive hip laxity, the position of
the patient is very different from the hip-extended position. The hip-extended
position has been used for more than thirty years to screen hips for either
DJD, laxity or both. Laboratory studies, however, have indicated wide diagnostic
variability among radiologists in interpreting this view.
Further, through biomechanical testing, the hip-extended view was found
to mask the underlying true joint laxity and through direct comparison,
the predictive value for CHD was shown to be inferior to the Penn HIP procedure.
Most importantly, the heritability of the diseased phenotype scored in the
hip-extended view has not been studied in most breeds of dogs. A knowledge
of heritability is critical to determine whether selection pressure will
produce genetic change. Estimates for the heritability of passive hip laxity
drawn from analysis of full pedigrees for the breeds examined thus far in
the studies show high values (for German Shepherd Dogs,heritability=0.61).
Fourth,the Penn HIP method is based on strict quality control. To take Penn
HIP radiographs, veterinarians must undergo training and a certification
process to demonstrate competency. The data generated from Penn HIP undergoes
regular review and statistical analysis so that useful information, by breed,
is available to judge progress toward reducing CHD. For optimal validity,
it is mandatory that all Penn HIP radiographs be submitted for analysis
and inclusion in the Penn HIP database. This policy eliminates the practice
of prescreening radiographs and sending only the best for evaluation, resulting
in biased hip data for any given breed.
What Happens to My Dog During a Penn HIP Evaluation?
To obtain diagnostic radiographs, it is important that the patient and the
surrounding hip musculature be completely relaxed. For the comfort and safety
of the animal, this requires sedation, however, some veterinarians prefer
general anesthesia. Typically, three separate radiographs are made during
an evaluation. The first is a compression view where the femurs are positioned
in a neutral, stance-phase orientation and the femoral heads are pushed
fully into the sockets. This helps show the true depth of the hip socket
and gives an indication of the "fit" of the ball in the socket.
The second radiograph is the distraction view. Again, the hips are positioned
in a neutral orientation and a special positioning device is used to apply
a harmless force to cause the hips to displace laterally. This position
is the most accurate and sensitive for showing the degree of passive laxity.
Passive laxity has been shown to correlate with the susceptibility to develop
DJD. A hip extended view is also included for the sole purpose of examining
for any existing joint disease such as osteoarthritis. The Penn HIP procedure
has been safely performed on thousands of patients.
What Is the Cost of Having My Dog Evaluated?
The total fee for a Penn HIP evaluation is determined by the veterinarian
providing the service. It is important to remember that the total service
includes sedation/anesthesia, three radiographs, office consultation and
all charges associated with mailing and film evaluation. You will not find
it necessary to write a separate check for evaluation fees or mail your
dog's films. The veterinarian performing the procedure is responsible for
payment and film submission. The film evaluation charge (currently $25.00)
will be included in the total cost of a Penn HIP evaluation.
Is Penn Hip to Replace other commercially available systems?
As technology advances, the veterinary professional community will offer
and utilize improved methods of disease diagnosis. The dog breeding community
will also endorse those methods that help them achieve their goals of reducing
the frequency of hip dysplasia in dogs while maintaining other desirable
traits and features. The Penn HIP technology and research have been, and
will continue to be, fully presented to the veterinary medical community
for its review. Penn HIP has been received enthusiastically as a major step
toward reducing the frequency of CHD. We encourage and welcome continued
scientific examination and comparison of Penn HIP to any available or new
methods of canine hip dysplasia diagnosis.
Will AKC and Other Breed Registration Organizations "Recognize"
Penn HIP?
ICG is working with many organizations to present the Penn HIP technology
and the positive impact it holds for reducing Canine Hip Dysplasia. It is
conceivable that at some point a Penn HIP reference might be included as
part of the dog's registry information. However, all hip evaluation reports
are considered confidential medical information and are released only to
the Penn HIP veterinarian and the owner of the dog (unless the owner requests
otherwise).
How does this benefit me as an owner or breeder of dogs?
Scientific data confirms that the Penn HIP method surpasses other diagnostic
methods in the ability to accurately predict susceptibility to developing
CHD. The method can be performed on dogs as young as sixteen weeks of age
compared with two years using the standard technique. The ability to receive
an early estimate of a dog's hip integrity is important whether the dog's
intended purpose will be for breeding, for working or as a family pet. The
data generated by Penn HIP will allow breeders to confidently identify the
members of their breeding stock with the tightest hips. The Penn HIP interpretation
will also permit breeders to assess the progress they are making with their
breeding program as they strive to reduce the amount of hip laxity in their
dogs. Pet owners are able to assess their pet's risk of developing CHD,
and make lifestyle adjustments for their dog, if necessary, to enhance the
quality of their pet's life.
How can I get the name of a Penn Hip veterinarian or get answers to additional
questions
To obtain the name of a veterinarian near you who is trained and certified
to perform the Penn HIP procedure, call ICG at 1-800-248-8099. If there
is not a veterinarian near you presently, additional veterinarians are being
trained throughout the country. If your veterinarian would like to learn
more about Penn HIP, please have him/her contact ICG directly.
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