Waggerland Cardigan Welsh Corgis

Canine Hip Displasia

Canine hip dysplasia (CHD) is a developmental trait primarily affecting medium and large breed dogs but it is also known in

Cardigan Welsh Corgis. Many Cardis who are diagnosed with affected hips however do not seem to suffer a lot from this

defect and manage to live their life to the max.

CHD is characterized by faulty conformation and laxity of the hip joint that usually affects both hips. It can be detected

radiographically as subluxation of the affected hip. The eccentric load on the articular surface of the femoral head (ball) and

acetabulum (socket or cup) leads to erosion of the cartilage, inflammation in the joint, and debilitating pain. Clinically, the

osteoarthritis or degenerative joint disease that results from hip dysplasia is characterized by hind limb lameness, reduced

exercise tolerance, reluctance to jump, and poor hind limb muscle mass.

There are several methods for scoring CHD. In The Netherlands the x-rays are rated by a panel of three expert evaluators

assigned for this task by the Dutch Kennelclub, this department is known as GGW (Health, Behaviour and Wellbeing). Cardis

can be evaluated from the age of 12 months. In the Netherlands we get an evaluation based on FCI regulations. Because of

this it should be possible to compare the scores between the different countries. Today we still see different scores in our

breed in certain FCI countries, it raises the question whether the hips of these dogs are of less quality or if there is a different

method of scoring within the FCI countries.

Then there is the Orthopedic Foundation for Animals that scores hips. Many Cardigan hips have been evaluated by the OFA

and many results can be found in the OFA’s database.

The phenotypic evaluation of hips done by the Orthopedic Foundation for Animals falls into seven different categories. Those

categories are Normal (Excellent, Good, Fair), Borderline, and Dysplastic (Mild, Moderate, Severe). Once each of the

radiologists classifies the hip into one of the 7 phenotypes above, the final hip grade is decided by a consensus of the 3

independent outside evaluations. Examples would be:

Two radiologists reported Excellent, one Good—the final grade would be Excellent

One radiologist reported Excellent, one Good, one Fair—the final grade would be Good

One radiologist reported Fair, two radiologists reported Mild—the final grade would be Mild

The hip grades of Excellent, Good and Fair are within normal limits and are given OFA numbers. This information is accepted

by AKC on dogs with permanent identification and is in the public domain. Radiographs of Borderline, Mild, Moderate and

Severely dysplastic hip grades are reviewed by the OFA radiologist and a radiographic report is generated documenting the

abnormal radiographic findings. Unless the owner has chosen the open database, dysplastic hip grades are not in the

public domain.

Excellent: this classification is assigned for superior conformation in comparison to other animals of the same age and

breed. There is a deep seated ball (femoral head) which fits tightly into a well-formed socket (acetabulum) with minimal joint

space. There is almost complete coverage of the socket over the ball.

Good: slightly less than superior but a well-formed congruent hip joint is visualized. The ball fits well into the socket and good

coverage is present.

Fair: Assigned where minor irregularities in the hip joint exist. The hip joint is wider than a good hip phenotype. This is due to

the ball slightly slipping out of the socket causing a minor degree of joint incongruency. There may also be slight inward

deviation of the weight-bearing surface of the socket (dorsal acetabular rim) causing the socket to appear slightly shallow.

This can be a normal finding in some breeds however, such as the Chinese Shar Pei, Chow Chow, and Poodle.

Borderline: there is no clear cut consensus between the radiologists to place the hip into a given category of normal or

dysplastic. There is usually more incongruency present than what occurs in the minor amount found in a fair but there are no

arthritic changes present that definitively diagnose the hip joint being dysplastic. There also may be a bony projection present

on any of the areas of the hip anatomy illustrated above that can not accurately be assessed as being an abnormal arthritic

change or as a normal anatomic variant for that individual dog. To increase the accuracy of a correct diagnosis, it is

recommended to repeat the radiographs at a later date (usually 6 months). This allows the radiologist to compare the initial

film with the most recent film over a given time period and assess for progressive arthritic changes that would be expected

if the dog was truly dysplastic. Most dogs with this grade (over 50%) show no change in hip conformation over time and

receive a normal hip rating; usually a fair hip phenotype.

Mild Hip Dysplasia: there is significant subluxation present where the ball is partially out of the socket causing an incongruent

increased joint space. The socket is usually shallow only partially covering the ball. There are usually no arthritic changes

present with this classification and if the dog is young (24 to 30 months of age), there is an option to resubmit an radiograph

when the dog is older so it can be reevaluated a second time. Most dogs will remain dysplastic showing progression of the

disease with early arthritic changes. Since HD is a chronic, progressive disease, the older the dog, the more accurate the

diagnosis of HD (or lack of HD).

Moderate Hip Dysplasia: there is significant subluxation present where the ball is barely seated into a shallow socket

causing joint incongruency. There are secondary arthritic bone changes usually along the femoral neck and head (termed

remodeling), acetabular rim changes (termed osteophytes or bone spurs) and various degrees of trabecular bone pattern

changes called sclerosis. Once arthritis is reported, there is only continued progression of arthritis over time.

Severe Hip Dysplasia: assigned where radiographic evidence of marked dysplasia exists. There is significant subluxation

present where the ball is partly or completely out of a shallow socket. Like moderate HD, there are also large amounts of

secondary arthritic bone changes along the femoral neck and head, acetabular rim changes and large amounts of abnormal

bone pattern changes.

Here is a table that shows the different scoring methods.

OFA	FCI (European)	BVA (UK/Australia)	SV (Germany)
Excellent	A-1	0-4 (no > 3/hip)	Normal
Good	A-2	5-10 (no > 6/hip)	Normal
Fair	B-1	11-18	Normal
Borderline	B-2	19-25	Fast Normal
Mild	C	26-35	Noch Zugelassen
Moderate	D	36-50	Mittlere
Severe	E	51-106	Schwere

Then there is the PennHIP method. To go short: The PennHIP method is a novel way to assess, measure and interpret hip joint

laxity. It consists of three separate radiographs: the distraction view, the compression view and the hip-extended view. The

distraction view and compression view are used to obtain accurate and precise measurements of joint laxity and congruity.

The hip-extended view is used to obtain supplementary information regarding the existence of osteoarthritis (OA) of the hip

joint. (The hip-extended view is the conventional radiographic view used to evaluate the integrity of the canine hip joint.) The

PennHIP technique is said to be more accurate than the current standard, and it has been shown to be a better predictor for

the onset of OA.

The radiographs pictured here are of the same dog, yet the hip joint laxties in each view look very different. Notice that the hips

in the distraction view appear to be much looser than they do in the hip-extended view.

Distraction View

Compression View

Hip-Extended View

The obvious contrast in joint laxity between the distraction and hip-extended views demonstrates

the fundamental difference between the two radiographs. The looser the joint on the distraction

view, the greater is the chance that the hip will develop OA. The hip-extended view tends to

mask true hip joint laxity because the joint capsule is wound up into a tightened orientation when

the hips are extended. This explains why measurable joint laxity on the distraction view is always

greater than the measurable laxity from the hip-extended view. In fact, distraction laxity is up to 11

times greater depending on the breed of dog under study.

The compression view is used to determine the "goodness of fit" of the femoral heads into the

acetabula. In a hip with OA, the remodeling that occurs in the acetabulum and/or the femoral head,

will often result in an ill-fitting "ball" and "socket".

To summarize, PennHIP method:

Obtains OA readings from the standard hip-extended view

Obtains hip joint congruity readings from the compression view

Obtains quantitative measurements of hip joint laxity from the distraction view

CHD in dogs is an inherited, polygenic trait in which mutations in several genes called quantitative trait loci (QTLs) contribute

to its clinical expression. Many dogs with normal hips on radiographs carry at least a modicum of the trait-causing mutations

but not all that are necessary to cause physical expression of the trait. CHD is a quantitative or complex trait that is expressed

as a continuum from imperceptible to severe forms. This continuum of trait expression is due to environmental influences

(such as plane of nutrition and exercise, as well as other unknown factors) which interact with the genetic constitution to

affect the degree to which the trait is manifested.

CHD has a heritability between 0.20-0.7. This means that between 20 and 70% of the physical appearance of the hips of each

dog in a pedigree can be attributed to its genetic relationships within the pedigree.

It will take a concerted effort to rid breeds of the genetic mutations that cause CHD or conversely, to introduce protective

alleles at the loci that cause good hips. Selective breeding based on current radiographic methods can reduce the frequency

of CHD in a population. Breeding two dysplastic dogs can yield a 75% incidence of hip dysplasia in offspring, while

mating two unaffected dogs can yield a 25% incidence of the disease. Selective breeding using normal dogs from

normal parents and grandparents, as well as progeny testing, should decrease the incidence of CHD.

Until there is a genetic test for CHD, so we can detect genetically susceptible dogs, the best indication of a dog's genetic

makeup is where it came from (its' parents and grandparents), what it produces (its' offspring), and the phenotype of its'

siblings or half sibs. Dogs with normal hip radiographs that carry some of the mutations that cause CHD but perhaps not the

major ones, when bred to a mate that also carries some of the mutations for CHD, may produce affected offspring.

To test whether a dog carries some of the mutations (even if the dog has OFA-good hips), it should be bred to sires or dams

with good hips and the proportion of affected offspring recorded (progeny testing). As many as 15-20 offspring should be

produced to be reasonably sure that the parents do not carry important mutations. This is an unreasonable burden for dog

breeders to bear. Breeders should attempt to breed dogs with the best hips in their colony as well as to dogs with

the other optimal breed characteristics and temperament.

At the Cornell University Hospital for Animals in New York they have been searching for the genes that contribute to hip

dysplasia. When an owner comes to this hospital for hip radiographs, they are asked to donate a small sample of blood from

their dog for DNA isolation. This DNA and the hip radiograph measurements are then used later to discover and confirm the

mutations that contribute to hip dysplasia. Once they know which genes and biochemical pathways lead to good and poor hip

conformation, they can develop novel treatments which can be applied at an early age.