THE SITUATION TODAY: SLOW
PROGRESS AND WHY
Why, after nearly some four decades of awareness, breeding changes, and
study, do we continue to hear from disgruntled or dissatisfied dog buyers
and breeders? Knowing that orthopedic disorders are almost all genetic,
one might think that it would be a simple answer to just breed non-carriers
of HD or ED (elbow disorders), or those with the best genetic bank for good
joints, but it is discovering these dogs that is the challenge. I should
address elbows in a separate article, but shall discourse on hips herein.
Now that we have good diagnostic tools and effective hip registries, the
next step toward progress is for each breeder to develop a breeding program.
Fortunately, some breed clubs and other organizations have already done the
greater part of laying a foundation. We have already potentially removed
one of the two major obstacles to progress, lack of understanding — or in
other words, a lack of good diagnostic guidance. After decades of using the
hip-extended method, most or all of those agencies have not generated a reliable
heritability figure for hip phenotype, nor has the method used in North America
reduced the incidence of HD as an average, across the breed populations.
Even when we look at subsets of canine populations in the serious hobbyist
world, we find that progress has stopped. We have reached a plateau in most
breeding programs, whether we speak of individual or group (club) efforts.
One reason is the failure to adopt the better diagnostic techniques developed
in recent decades.
The other reason for spotty, slow, or inconclusive progress in reducing
and ultimately eliminating canine HD is non-compliance: the failure of most
breeders to stick with a really vigorous program of control and reduction.
As you might think, some breeders do their best to provide an environment
that causes the least dysplasia. However, genes that induce HD will
thus be masked and therefore retained in the stock. Few breeders are
likely to provide knowingly the adverse eugenics environment that would
reveal such genes. Part of that second reason (breeding practices) for slow
progress is the win-at-all-costs attitude maintained by many of the more
prolific breeders and leaders of breed clubs. One of my correspondents,
a friend and a widely respected veterinary researcher, wrote, “Many of the
breeding [genetic] defects do not hit the breeder in the pocketbook and winning
in the show ring is all that’s important.” (personal correspondence
with J.W. Bardens, 1986) This neglect is why the Select class of the
annual German Shepherd Dog Club of America National Specialty Show, consisting
of the top 20% or so in that class (on that day) has seen a quality decline,
both orthopedically and in other areas of soundness. From 1983 through
1991, the Select dogs (males) that had an OFA hip certificate dropped from
78% to 31%; the Select bitches fell from 44% to 7% in the same period. Later
statistics are no better. You are hard pressed to find AOE (Award of Excellence)
dogs among the GSDs of the GSDC-America; these are dogs that not only have
placed very high at the National and have a rudimentary obedience degree,
but also are certified normal in hips and elbows.
In some parts of the world, organizations and individuals have made greater
strides than those in North America have, but there is still a way to go.
The requirement in Germany for all radiographs to be recorded and dogs’ results
made known, is admirable. The “sometime-pressure” in the UK for vets to
cooperate by sending in all films and getting the results posted in the
GSD database founded by Dr. Malcolm Willis has helped a little. I have received
only bits of information from Shepherdists or vets “Down under” since the
last time I judged and lectured in New Zealand and Australia, but the Kiwis
and Aussies also have room for improvement, as the following example would
indicate:
Recently, I received a request for advice and counsel from a breeder in
Australasia who has been conscientiously trying to avoid and reduce problems
with hips and elbows. He allegedly sold a pet price bitch (no guarantees),
paid for the 12 month radiograph, and got a BVA-type score of 11 in the
Australian hip scheme. When the bitch was approximately 3 years old, the
buyers decided they wanted to breed her, had her re-radiographed, and reportedly
the score was 81. Now, 11 is pretty good but 81 certainly is not,
and that led to a complaint being filed with the national Kennel Club, which
organization does not regulate hip schemes, I am told. The breeder faces
“a long ban” because of the accusation that he did not supply the “correct
hip score” those few years ago.
There are two likely reasons for the two different readings, and I suspect
both are involved, even though the bitch has no clinical signs. One is the
inaccuracy of the supine, legs extended procedure used in diagnosis in Australasia
and the bulk of the rest of the world. The other is the fact that loose hips
do, indeed, change over time, and it is the rule rather than the exception
that loose hips at a young age (even if undetected by old methods) will be
even looser at an older age, and that DJD (degenerative joint disease, arthritis,
remodelling) is more likely then. If the prevailing culture and conventional
wisdom amongst breeders and vets in New Zealand and Australia ignores the
newer, improved, more accurate techniques, can they rightly blame the average
breeder? If he was operating with what light he had provided to him by his
peers and leaders, is it right to blame him for a change that is most common?
If the facts are as presented, then action against him is unfair and unwarranted.
PROGRESS IN THE UNITED KINGDOM
Before getting back to the penal colonies and Oceania, let’s look at Britannia
itself. England, Scotland, Wales, and to a lesser extent countries with historical
ties to England, such as Ireland, Singapore, “OZ and NZ”, and a few others
have the potential for making great strides in reducing HD. Part of the
mechanism is in place; what breeders need to do is use it. However, it may
be difficult to accomplish without government legislation or regulation by
breed clubs and The Kennel Club, which should restrict registration without
proof that the parents’ hips meet certain standards. After all, the Brits
are used to socialism and the intrusion of government into such areas as
hobby breeding and showing that Americans take to be none of Uncle Sam’s
business. Whether by gov’t force or voluntary peer pressure, I would like
to see a reconfirmation of phenotype normalcy after 2 years of age. Where
the UK scheme continues to fall short of being ideal, besides certifying
at an early age, is in not requiring all films to be submitted the statistical
study.
The BVA system concerns nine features, but for practical purposes, only
a couple are really important, those being subluxation and Norberg angle
(these two identifying laxity) and all others put together as a description
of degenerative changes. Values of zero (no irregularities) to 6 (horrible)
are given to both left and right hips joints, and the columns added. The
totals are reported in terms such as 3/5, 0/0, 21/18, etc. Adding both column
totals together and coming up with a 20 or higher would stop most people
from breeding such a dog, and most good breeders refuse to use any dog with
a grand total of anything more than 10.
Currently, radiographs of dogs in the UK are sent to 2 of 10 radiologists
on a rotation basis. They grade the 9 features and send their evaluations
to the chief scrutineer, who then gives the data to the geneticist (Dr. Malcolm
Willis, in many breeds) who in turn reports in a form useful to breeders.
He also compiles data on those breeds in a number of other countries for
their club members’ use. Thanks largely to the German Shepherd Dog League
and other fanciers of the UK, the British Veterinary Association’s scheme
was adopted or copied in several countries historically connected to the
old Empire. The BVA/GSDL scoring scheme has been expanded to all breeds and
will again be seen to have taken the name of the BVA/KC scheme while retaining
the improved features of the GSDL one.
Besides giving a quantitative score, the BVA/GSDL scheme also has another
important advantage for breeders over the American OFA and some other systems:
it does produce information on progeny for several breeds. Computer-retrievable
data by kennel name, sex, birthdate, age at time of radiography, and numerical
value for each hip are used for genetic analyses and for your own conclusions
on with whom to breed Schatzie, or whether to breed at all in deference to
waiting to buy a better dog. Say you like the looks of that dog that
placed in the Top Ten at his breed’s national specialty show the past two
or three years. You look up his published hip scores, the mean score of
his offspring who are old enough to be assessed, and scan the column that
tells you whether and by how much he improved on the hip scores of bitches
he previously bred. If your breed club doesn’t have that information,
and it’s likely it doesn’t, then it isn’t doing all it can to serve you and
your breed. That’s where “politics” can have a rare, beneficial effect on
purebred dogs and the sport. Get into or start a movement to require your
national club to hire a geneticist and give instructions to set up a scheme
similar to that now employed by BVA/GSDL. Yes, you can go it alone, but your
choices of breeding animals will be more limited than if you were backed
with the power of a club like the U.K.’s GSD League or the GSD Council of
Australia.
However, despite the UK’s German Shepherd Dog clubs, through the GSD League,
being responsible for developing one of the most advanced information and
control schemes in the world, the mean scores for GSD males and females born
since 1959 have not changed a whit. About 45% of the UK’s GSD’s have scores
of 10 or below, with most considering the really “normal” ones as being
in the 0-5 range and the 6-10s being equivalent to what we might call “near
normal”. BVA scores as high as 20 could encompass the level of quality given
the ‘A’ stamp in Australia (not the same meaning as the FCI’s “A” designation
for normal hips), but allowing that many dogs to breed will slow the progress,
regardless of breed or country. Much better to make the requirements more
strict each year until something approaching the Swedish model can be had.
Examples of progeny data are often seen in tables published in breed magazines
in the UK and British influenced countries. The first column after the dogs’
names gives the number of progeny that were scored by the BVA. The
second column shows the numbers of those progeny whose dams were also scored,
and the third column lists the number of different bitches each sire was bred
to in producing those offspring. Important data include the mean score of
those progeny, and the distribution. Obviously, those sires that produce
higher percentages in the 0-5 score category and (of slightly lesser importance)
a close second high percentage in the 6-10 column, are the most desirable
for improvement in hips and should be preferentially bred to, as long as
they also produce other important good features.
The “change over dams” column represents valuable information when coloured
by other data. Dogs with a large minus figure here have sired animals
with that much lower (better) mean hip score than the dams had. Of
course, a good male bred only to 0/0 bitches will show a plus sign here since
the offspring will not be as good as their dams, but if the mean score is
low, the “change over dams” information diminishes a little in importance.
A dog bred to high score (high HD risk) bitches would show a high minus value,
but the progeny scores will not be as good. As such a scheme with
its published data becomes more used, there will be fewer stud owners willing
to tarnish their dogs’ reputations by agreeing to breed to a poor producing
bitch or one that has less desirable hips herself, and fewer breeders willing
to overlook orthopedic soundness in favour of one or two flashy characteristics
in a stud dog. A similar thing is happening in Germany, where breeding to
a high-ZW bitch (bad) will raise your stud dog’s own good, low ZW because
the pups will not have as low an average.
While many breeds have entered into the BVA/GSDL scheme in Great Britain,
only the German Shepherd Dog breeders in various other countries have participated
significantly so far. Smaller numbers and a combination of apathy and
inertia may be reasons. Still, for those tabulating and disseminating
information on progeny, the prospects for great improvement are equally great.
Willis in the UK furnishes data on percentages of dysplastic dogs vs. normals,
produced by both dogs and bitches in an increasing number of breeds, and
extends this to other countries with similar or shared bloodlines.
PROGRESS IN AUSTRALASIA
I was an honoured guest and minor judging participant at Australia’s 1991version
of a “Sieger Show”, the only foreigner to have been so honoured up to that
date. It is called the “Main Breed Assessment” rather than a “show”, to avoid
problems with the quasi-governmental Australian National Kennel Council over
practices allowed at regular shows, such as pedigrees and catalogues in
the judges’ hands, gun sureness testing, and especially information on what
problems and good features the dog being examined has passed on to its pups.
I was very impressed that, in coming to the placement decisions, the judges
of the adult classes took into account such things as the Australian ‘A’
stamp hip status (they capitalize the letter down under) of the individual
as well as of siblings and offspring, and other genetic factors as well as
a full and expert evaluation of the dog in question. As mentioned earlier,
the BVA/GSDL scheme caught on so well that several countries apart from the
British Isles have adopted it, or in the case of the GSD people in Australia,
the breeders use it modified in conjunction with their own system. At the
time I was last there before preparing this edition, 40.5% of the GSDCA dogs
scored 0-5, and another 26.5% scored 6-10 in the BVA scheme. The GSDCA uses
a 6-grade scheme when they might be better off just using the 106-point spread
the BVA uses. They give the ‘A’ stamp to too many animals for fast enough
progress. The 6 grades are: N, NN, A, BL, III, and IV. Dogs are considered
eligible for the ‘A’ stamp if they have one of the four top grades of the
six, and this includes A and Borderline (many of which have what OFA would
call mild to moderate HD). As in Germany, this allows too many to breed,
and tends to act as a brake on progress. However, they have what we
in North America don’t have to any appreciable amount: progeny data; this
tends to offset part of the failings of less strict radiograph requirements
in comparing those schemes to OFA’s.
According to an issue of the Australian GSD clubs newsletter, almost all
of the Normals (in their breed) and 61.4% of the Near-Normals score 0-5;
the other 38.3% NNs score 6-10, along with 75% of all the A grades.
Some 56% of the Borderlines (BL) scored 6-10, but 40.8% score 11-15.
Most of the grade IIIs score from 11-20. The use of the Willis statistics
as breeding aids have attracted the notice of other breed people in Australasia
as well, so more dogs there will benefit from the emphasis on hip radiography,
open records, and progeny testing in the future. Already, several of the working,
herding, and sporting breed clubs are beginning to participate.
In quality of type, Australia has probably made the greatest overall progress
in the German Shepherd Dog breed of any country in the world, though not
as much in quality of hips. This has been done while coming from a period
of a ban on imported dogs and mandatory neutering of those already in the
country. In only a few generations, they produced a world class German
Shepherd Dog with great uniformity and overall soundness. They are forbidden
to use Schutzhund-type courage testing, because of the threat of the import
or breeding bans being re-instituted, but in all other aspects the Australian
GSD is pretty much the equal or superior to its counterparts elsewhere in
the world. I expect them to put as much importance on orthopedic soundness
as they have on breed type.
While hip quality has not increased as dramatically as quality of type,
there are hip requirements for breeding and, in time, increased strictures
will produce faster improvement. Figures for the distribution of hip
evaluations in German Shepherd Dogs in Australia showed 48% graded normal
or near normal (about evenly split, and both being given the ‘A’) in the
earlier years of controls. A later report indicated 11% borderline, 11% grade
III, and 17% grade IV, perhaps showing that such a program can reduce the
incidence of the worst grades. By limiting breedings to animals with
the ‘A’ stamp, the Aussies and Kiwis would exclude about a third of the breed,
better than what was done in England, but far inferior to Sweden and what
had been required in East Germany. Since 1981, the percentage of Australian
GSD's receiving the ‘A’ stamp has risen from 60% to 80%, while grades III
and IV (roughly equivalent to moderate and severe HD in the United States
or the BVA scores of 0-10) have declined by half.
New Zealand, a two island country the size of California but with far
lower population, also participates in the BVA scheme, with radiographs
read by a panel of six or eight “scrutineers”. Between 300 and 400
films a year are sent to the panel head, who forwards them to the panel in
batches of 20, thence to such as Professor Norman Williamson, then head of
the Department of Clinical Sciences at the veterinary school in Palmerston-North,
and readings with pedigree and other information are sent to Dr. Willis
in England. Many New Zealand dogs fly to Australia to compete in the
larger shows there, and bloodlines are very much in common.
JAPAN and PACIFIC RIM
In the modern, dog loving portion of Japan's society, progress in control
of hip dysplasia is just around the corner. I have judged and lectured there,
and long ago found great interest in improvements in many areas. The Japan
Kennel Club adopted PennHIP as the official and preferred HD diagnostic procedure
in the late 1990s. In Taiwan, dog shows and interest in improved breeding,
including for better hips, are on the increase.
AMERICA vs. the WORLD
The oldest hip registry is the Orthopedic Foundation for Animals, but
there are others, most notably GDC and PennHIP. It’s a good thing that OFA
requires a minimum age of 24 months for certification of “normalcy”; otherwise
the situation in most breeds in the USA would be dismally poor. And
in most breeds it is not that great, anyway, if you look at over-all breed
statistics instead of individual breeders’ accomplishments. Paradoxically,
the greatest rates of progress are in some of those countries where dogs
are radiographed and certified for breeding as soon as they pass their first
year’s birthdate, although they would be even better if approval were to be
delayed at least 6 more months. The reason, though, is that many breed clubs
outside America control authorization for breeding and registering. In America,
the AKC gleefully registers anything that comes with money and the specified
paperwork.
Compare progress in the U.S. with that in Germany, for example, and specifically
the most popular breed there and in the world, the German Shepherd Dog. There
has been a shift toward normalcy that came about in spite of only those
with severe HD being forbidden breeding rights. As time went on, requirements
for the VA or Auslese (excellent-select) class at the world Sieger Show in
Germany were tightened more and more. Not only must current high placing show
dogs have advanced training degrees, they must also have the better hips
and produce a good number of normal hips as well as structurally desirable
progeny. Today a dog with a Noch Zugelassen rating might make it into the
VA class of some eight or ten out of hundreds of competitors, but he or she
will not win the top title of Sieger or Siegerin, and there is now pressure
to keep the bad producers (with high ZW numbers) from being honoured with
the Sieger title. There is annually increasing emphasis that the very top
be Normal, not just Fast (nearly) Normal. So the dogs that get the most breedings
in most of Europe generally have the best hips. There is no similar restriction
in the sizeable Select class, neither at American (U.S.) national specialty
shows, nor at the smaller but similar Canadian Nationals. Nor is there anything
similar in the other AKC- or CKC-affiliated breed clubs. In Germany, the
VA (“Excellent-Select”) at the main breed show generally only goes to dogs
with parents who have the better hips. In America we have neither the strict
rules nor the peer pressure nor strong suggestions to judges. We certainly
aren’t allowed to officially “know” the hip status or other information important
to the breed when we judge.
SV data show not only an increase in the number of submittals for evaluation
corresponding to increases in both population and breeder/fancier involvement,
but also a gradual increase in number and proportion of “a”-stamp Normals.
Concurrently, we see a slight increase in the “near normals” at the expense
of the mildly dysplastic but “still permissible” (noch zugelassen) population.
Clearly the SV’s program has shifted the percentages toward the better side
of the table. Even faster progress could have been made by the SV if
they awarded the “a” stamp only to dogs radiographed after 18 or 24 months
of age. And in other countries we could see an increase in the progress rates
if all dogs were to be radiographed and evaluated, even if they had poor
hips and would never be bred. It would give valuable data for progeny testing
— find out which dogs are producing those whose hips were expected to fail
and thus were not entered into the evaluation scheme.
Later Improvements
Two movements in America arose in the past decade or two that promise
better progress than given by adherence to OFA numbers as the way to coxofemoral
nirvana. One is the proposal to use a voluntary “open registry”, and
that is promulgated by Centre for Genetic Disease Control (GDC), an organization
that in its earlier days has laudably focused our attention on the elbow
dysplasias that are big problems in some breeds, nagging ones in others. The
other is PennHIP (University of Pennsylvania Veterinary School Hip Improvement
Program). I had the pleasure of working with the OFA’s first “program director”,
Penn’s Dr. Wayne Riser, when I was researching and preparing my book, Canine
Hip Dysplasia, and I also have had the good fortune to visit Dr. Gail Smith
(PennHIP) in Philadelphia in the early 1980s. I reviewed his methods, philosophy,
and results, and am increasingly a supporter of this protocol. My experience
with “wedge” radiography, palpation, and follow-up OFA-AVMA radiographs had
convinced me that joint laxity is by far the leading indicator of incipient
dysplasia, and that early diagnoses or pre-diagnostic predictors are not only
possible but entirely feasible. For practical purposes, in most breeds, you
could say that laxity is dysplasia. Good statistical evidence has been developed
to prove that breeders (through PennHIP-licensed vets) can detect such sign
of future dysplasia and predict degenerative joint disease (arthritis) at
a pup’s early age. Early enough to cull it or them from the breeding
programs, start over with better stock, choose better partners, and improve
the general welfare of their chosen breed. Or at least the quality
conscious portion of the breeding publics will do this. As of the date of
this writing, only PennHIP has the accuracy, repeatability, precision, and
scientific foundation for real and rapid progress in producing better hips.
Can progress be satisfactory when using an approach that utilizes exclusively
the hip-extended position? Yes and no. As is the case in any subjective method,
and analogous to the differences between artists, much depends on the skill
and standards of the individual. The California guide dog school’s improvement
under the leadership of Renner and Giardina that is referred to in some
of my articles on the “realgsd.net” website is an example. But they used
a combination of Bardens palpation, wedge radiography, adult evaluations,
and progeny testing. In the years this program was implemented, those
were the only tools at hand. A larger scale and more scientific “modified
OFA evaluation procedure” was reported in the May 13, 1997 issue of JAVMA.
Dr. Eldin Leighton, geneticist at The Seeing Eye, Inc.® was in large
part responsible for that east coast guide dog school's notable genetic progress
since 1979, in which the incidence in their breeding program dropped from
59% to 24% — again, using the leg-extended position. However, the big difference
in this independent investigation was that they also utilized calculated
breeding values (BV), which is the scientific, statistical side of progeny
testing (the Germans call it Zuchtwert). Most breeders, in contrast, use
mass selection based only on phenotypes of the individual prospective breeding
partners. Leighton later added the PennHIP protocol and got even faster progress.
Another important factor in the progress rate with the standard AVMA position
at The Seeing Eye was the use of Dr. Darryl Biery, a board certified radiologist
who had been known to interpret hip radiographs more strictly than the OFA
did. The combination of these factors yielded real progress in the controlled
population of Seeing Eye candidates and breeding stock. Further, it demonstrated
that even a subjective hip score could be used to bring about genetic improvement.
Not as good as an objective method such as distraction index, but progress
nevertheless. This need for more rapid and sure progress is why Dr. Leighton
said, “To make further progress toward eliminating CHD, a measure of hip
quality that will allow us to distinguish among the dogs currently in the
breeding program is needed. For this reason, The Seeing Eye, Inc. has turned
to the distraction index (PennHIP) as a means of assessing hip quality”.
USE THE BEST TOOLS
As you
have already discovered, the major reasons for lack of further progress
in decreasing HD incidence in a colony or breed, or the purebred dog population
overall, are non participation (not screening partners with radiography)
and not using the best tools. The bar has been raised, to borrow a sports
(high jumping) term. No longer is it sufficient to rely on the old OFA or
BVA or Australian or New Zealand evaluations of the hip-extended (supine),
unstressed position. Veterinarians such as Graeme Allan at Sydney and Richard
Read at Murdoch in Perth have been trained in the PennHIP technique. At
the PennHIP training session and seminar in Denmark in the late 1990s, about
250 European vets availed themselves of the new knowledge. With enough pressure
from breeders in the rest of continental Europe, Australia, New Zealand,
the UK, and elsewhere, additional P-H-certified vets will become available.
You can learn more about the procedure if you are on Internet, by “tuning
in” to
Breed Value
The ZW (Zuchtwert, which is German for Breed Value) is a number that reflects
a rough estimate of the likelihood of producing good hips. It is an average
of the sire and the dam’s ZW, weighted toward the number of progeny each
has, and which have been evaluated. It has been used for several years by
such clubs as the Jagdterrier and Hovawart groups in Europe, has more recently
been adopted by the SV, and has been used for many years by The Seeing Eye®
guide dog school in the U.S. It is an old system that for many decades has
served the livestock and dairy industries well, and will also benefit the
dog breeding enterprise and sport. If breeders in Australia, New Zealand,
the U.K., and other countries that have suffered under (or enjoyed the protection
of) the antiquated and now crumbling quarantine system, can use with preference
the dogs with the lowest ZW (or BV) numbers, additional improvement will
occur. It is yet another of the latest and best tools that should be used.
Compression/Distraction Stress Radiographic Technique
Although it has been said that x-raying dogs in the standard ventrodorsal
position “can reveal abnormalities that cannot be detected in other positions”,
the primary indication of HD (or risk of later DJD) is joint laxity; this
best can be revealed in younger dogs by the PennHIP method employed and promoted
by the University of Pennsylvania. Before PennHIP started in the mid-1980s,
Cornell’s Dr. Lust had realized the need for a standardized method for applying
a force that would displace femoral heads from the acetabula, to demonstrate
what I dubbed covert laxity, and providing an objective measurement of that
displacement. The PennHIP method provides these measurements and is a modification
or perfection of the wedge technique, with important improvements. Lust
has called PennHIP’s “more physiological position… [and] improved assessment
for joint laxity” [Canine Chronicle Sept 10, 1988] both promising and useful
for diagnosing HD in young dogs.
At Penn, Dr. Gail Smith, a veterinary surgeon with an additional
PhD in engineering, along with his radiologist colleague, Dr. Darryl Biery,
refined the concept of the wedge, an earlier form of stress radiography in
which force is used to lever the femoral heads out of the acetabula if laxity
is present. It is variously known as the compression/distraction method or
technique, or by its commercial designation, PennHIP, which stands for Pennsylvania
Hip Improvement Program. You cannot, by the way, damage the hips with this
procedure any more than you would with the relatively unstressed hip-extended
methods. Even performing forceful techniques on cadavers (the ultimate in
anaesthetic relaxation) failed to show laxity in dogs that were normal in
hip joint tightness before death (personal communication with E. A. Corley,
1982).
The PennHIP method is effective in diagnosing the prime aspect or predictor
of HD (laxity) in dogs as young as four months. Smith once said that he believed
his method at four months was 80 percent as accurate as the standard AVMA/OFA
diagnosis at twenty four months. Later statistics indicate that it is 96%
accurate at four months and nearly 100% accurate by six months, when compared
to radiographic evaluation done at twelve months of age. Laxity does not
change appreciably over the dog’s lifetime, especially if the joints are
relatively tight to begin with. Accuracy, however, is not well defined in
the context of making genetic change toward better hips. For that, you need
to add the effect of heritability. The hip phenotype with the highest heritability
is one that should be considered most accurate. And the distraction method
has a much higher heritability than older methods of viewing hips.
The position utilized in PennHIP is that of a dog that looks like
it is standing, but the picture is upside down. For a long time I knew that
the extended leg AVMA standard view position actually “wound up” the joint
capsule, the ligaments and muscles around the hip socket, when the dog was
in that ventro-dorsal mode on its back on the table, but could not develop
a method to get a good radiograph of a standing dog. This AVMA and BVA supine
position thus tends to show a false, temporary tightness of the soft tissues,
often forcing the femoral head more tightly into the socket and making it
look like a deeper seat. The PennHIP method includes this extended leg position
because that give the best view of most DJD signs and, if the owner so desires,
a copy of this shot can be sent to BVA, OFA, GDC, etc. for their numbers
and the advertising value. For the other two P-H shots, the vet first seats
the heads of the femurs in the acetabula by pressing them in from the “outside”
(laterally), in case the dog has so much laxity that it would show with no
effort. In this way, all comparisons start equally, with heads as fully seated
in the acetabula as possible; in most dogs it demonstrates the concentricity
that is normal and desirable. Then, while still in the knees-up position
and still under anaesthesia, the distraction force is applied medially to
push the femurs apart and reveal latent or otherwise hidden looseness. This
force separates the centre of the femoral head circle (as superimposed on
the film) from the centre of the acetabulum circle, and the distance is measured
with the use of precisely machined steel circle gauges. A ratio is reported
and is called Distraction Index, DI. A threshold level of 0.3 (30% of
the way from no space to 100% out of the socket) is probably the best “feel
good” floor for the serious breeder, though other aspects must be factored
in; examples are characteristics such as working ability, health, breed type,
or temperament.
If, in this distractive view, there is no appreciable difference from
the picture taken with mild compression, the implication is that the volume
of synovial fluid is normal and that it tends to resist, like a suction cup,
the effort to pull the head out of the acetabulum. If, on the other hand,
there is too much fluid for a stable joint, suction plays a lesser part
and perhaps not until the head is pulled a considerable distance out. The
PennHIP compression/distraction technique can discourage some who have been
relying on AVMA false negative readings, when they see actual laxity using
the PennHIP technique.
The PennHIP compression/distraction technique might tend to discourage
some who have been relying on the false negative readings common to the hip-extended
view, when they see actual laxity using the PennHIP technique, but it is
better to face the facts than live in denial. Young dogs with loose hip joints
as shown by this method may not have readily apparent laxity with other methods
and positions. However, as the dog gets older, those that show greatest
laxity with Penn’s method develop obvious laxity with other diagnostic methods
and also show significantly more degenerative joint disease (arthritic changes).
With the PennHIP method, those dogs with tight joints as young as four months
of age retain tight hips throughout life. Those pups with loose hips at
this age develop a wide range of laxity in later life and a similarly wide
range of osteophytic deposits and changes in shape.
However, as the dog gets older, those that show greatest laxity with Smith’s
method develop obvious laxity with other diagnostic methods and also show
significantly more degenerative joint disease (arthritic changes). Perhaps
the major reason for the higher level of false negatives (seemingly, but
wrongly considered HD-free) in the standard extended hip ventrodorsal view
is that the joint capsule, which is in its most relaxed state when the dog
is standing normally, is now twisted to its maximum. When you older guys were
kids, and wound the rubber band attached to the model airplane’s propeller,
you saw how tightly if drew the prop against the front of the fuselage and
could image that if it weren’t for the rigid body of the plane, it would draw
the ends of that plastic band closer together. The same thing takes place
when the twisting of the ligaments and muscles around the coxofemoral joint
occurs as you extend the legs almost parallel with the pelvis and the table
and the dog’s spine. This pressure forces the head tighter into the acetabulum;
it has to be a substantially lax joint not to look normal in such a situation.
There are some dogs (usually of certain giant mastiff-family breeds) that
do not develop DJD but are OFA-assessed as dysplastic because of laxity at
two years’ age. Even more importantly, there is a greater number of dogs
of other breeds that are adjudged “normal” at two years but later develop
DJD or produce an unacceptably high percentage of dysplastic descendants.
Thus, the accuracy of the hip-extended methods is gravely flawed. Even if
reliability (by this is usually meant repeatability of results) is high from
younger ages up to the OFA’s two year qualification age for certification
or the 12 month stage for other registries, the absence of accuracy is worrisome
to breeders, and diminishes the importance of published (JAVMA, Nov. 1, 1997)
reliability figures. As an example, Penn cites the OFA-type evaluation of
military dogs in a longitudinal study (JAAHA, 1996) in which all the dogs
with normal hips at two years had mild degenerative changes by nine years
of age. At the same time, 22 of 52 dogs judged “positive” for HD at two
had similar changes by nine years! The conclusion is that the hip-extended
type evaluation at two years still gives a relatively high rate of misdiagnosis,
and blurs the distinction between true positives and true negative diagnosis,
even at that supposedly “safe” age of two years. For the breeder, who really
wants to know what his dog’s genotype is, the absence of radiographic signs
at two years when using the OFA-type view is not enough to give confidence
in the “true negative” or “normal” proclamation or implication that this
particular dog is relatively free of the genetic programming for HD. To a
breeder, such false negatives would mean a severe and expensive setback in
his goal to reduce or effectively eliminate HD in his kennel. The gene pool
is hurt most by these false negative diagnoses.
Using the Newer Procedure to Improve the Breed
It should not be surprising to anyone that the looser the hips,
the less accurate a prediction of a specific grade or severity might be.
HD is developmental (DJD might not show up right away), progressive (it'll
eventually be worse), and multifactorial (environment has a part to play
in the expression of the bad genes). Some dogs will get worse than others
even with the same DI at a young age. Some breeds (such as Rottweilers and
Saint Bernards) can tolerate looser hips than a GSD and, with identical DI
numbers, have less arthritic degeneration in maturity. There is very good
reason to presume that dogs that have no early signs of DJD yet have an index
higher than the mean for their breed “represent a carrier state of the disease”,
as mentioned in an AJVR (American Journal of Veterinary Research) report
to be found on the websites mentioned above. In other words, it is a clearer
picture of the genotype than the AVMA view gives. Man has advanced over his
prehistoric precedents by using more tools, and we should progress in use
of modern tools regarding HD as we have from the Neandertal era to the Stone
Age to the Bronze Age to the Machine Age, and to the Computer Age. PennHIP
is such an advanced tool for the serious breeder. The inescapable conclusions
are that:
1. Tighter Is better (agreed on by OFA, PennHIP, and all other groups);
2. Position and technique (better tools) can discover covert laxity;
3. PennHIP is the best diagnostic predictive tool currently available.
The pet owner of course wants a painful, long life for his companion.
That is reason enough to fight the battle against HD and elbow dysplasias,
as well as less prominent genetic disorders. Beyond the pet buyer, there
are two groups of fanciers very interested in improving the average and total
hip joint status in the breed. One group consists of the show and trial enthusiasts
who want to win recognition in competition, enjoy the capabilities of their
canine companions, and appreciate the camaraderie and activity in their
hobby. The other group is composed of the breeders. All three may overlap
— you may consider belonging to more than one category — but one objective
is common to all: we want better dogs with better hips for health, work,
and activity over a long life span. All three groups can benefit from all
three sides of this triangle of evaluating mature dogs for DJD, using PennHIP
for early risk detection, and following a Breed Value/ZW program. In my experience,
degeneration happens eventually and so regularly that (in some breeds more
than others) the dog owner can say that laxity practically is dysplasia.
The science is sound, the data is voluminous, the evidence is clear: it is
not worth it, in most cases, to breed dogs with excess laxity. But you must
find that laxity in order to make substantial progress.
PennHIP does not make breeding recommendations, only evaluations; it leaves
the decisions up to you, and counselling up to your veterinarian and peers.
If you get the PennHIP report and it says your dog is in the 50th percentile,
that means that 50% of its breed have tighter hips than it does, and 50%
are looser. In the 80th percentile means that your dog’s hips are tighter
than about 80% of the dogs in its breed, and the important lesson you have
learned from both OFA-BVA etc. and PennHIP is that “tighter is better”. You
are perfectly able to decide which dog is better for breeding from the standpoint
of hip joint quality and other characteristics. Naturally, you will want to
breed only those dogs that are in the higher percentiles and have a DI lower
than the mean (since the index increases in proportion to the laxity, smaller
is tighter). In addition, you will be informed by your vet or the Synbiotics
website what the current mean (average) DI is for your breed. The best progress
will be seen by selecting the lowest numbers, or at least those below the
mean, and breeding to a dog with a lower DI than your own dog’s. The higher
the DI number, the greater the risk.
If, as is certainly indicated, the DI gives a better picture of
future hip quality in your dog, then deductive reasoning would lead you
to think of it as a reasonably accurate indicator of the genotype of your
dog. That means a better idea of the proportion of bad hip genes to good
hip genes, which in turn means relatively how many bad genes are likely
to be transmitted to the next generation Now that, dear friends, is really
revolutionary. The lack of further progress we have seen in modern times,
with ratings by BVA, OFA, SV, ADRK, OVC, and other breed and veterinary
organizations is a direct result of their inability to indicate those hidden
genes. A dog that has a good picture in the extended leg view yet still produces
an unacceptably high number of dysplastic offspring has too many of those
hidden genes. Since OFA would be the first to tell you of the link between
laxity and HD (remember, they actually use that as a definition), the only
reason for the poor progress is the covert laxity I mentioned earlier. Therefore,
using the logical process of thought, if PennHIP shows more of this laxity
than shows up in the AVMA type view, it in effect shows us the effects of
more “hip genes”. Since mapping the dog’s genome (at least finding markers
for enough of the polygenic perpetrators) is decades away, the DI evaluation
as promoted by PennHIP is by far the best tool in our tool chest.
Fred Lanting is the author
of several books, including “The Total German Shepherd Dog” (available from
Hoflin.com or realgsd.net), and “Canine Hip Dysplasia”. He judges
and lectures world-wide, and since he retired, has been leading tour groups
of training and breeding establishments on the way to and from the Sieger
Shows in Germany. He is an SV breed judge and also does many Rottweiler
specialities. He can be contacted (eventually) at mailto:Mr.GSD@hiwaay.net
COPYRIGHT ©
Fred Lanting 
