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Canine Hip Dysplasia Quiz

The answers to this quiz have been developed in consultation with Dr. E. Al Corley, Project Director of OFA, and all
supporting quotations have been taken (with Dr Corley's approval) from the pages noted in parenthesis from his 1989
monograph on hip dysplasia: “Hip Dysplasia: A Guide for Dog Breeders and Owners”, co-authored with G.G. Keller.

The following is taken from Golden Retriever News, the official
publication of the Golden Retriever Club of America (GRCA).

Do you think you know a lot about hip dysplasia? Can you tell the difference between myth and fact? Here is a chance for you to find out just how much you do know about hip dysplasia. this quiz has been compiled from the most common facts and fantasies on the subject and can be answered TRUE or FALSE. All answers have been verified with Dr E. A. Corley DVM, Ph.D., the Project Director of the OFA, University of Missouri, Columbia, MO. Answers and commentary will appear in the next issue of Golden Retriever News.

To take this test, remember, you must be at least two years of age! If you score 10 right, you are OFA BORDERLINE and should be retested in 6 months. (In the meantime, it would be well worth your time to contact the OFA and request a copy of their most recent publication of hip dysplasia!) A score of 14 means you are OFA FAIR, and we recommend you "associating" with only with OFA GOOD or better! Sixteen right and you are definitely OFA GOOD! those who score 18 correct are OFA EXCELLENT. Your parents should be very proud that they were able to reproduce such soundness! However, should you be lucky enough to get a perfect score....well then, you are very jHIP!

1. If an OFA cleared sire is bred to an OFA cleared dam, you are guaranteed to have a litter of all OFA cleared puppies.

2. When evaluating soundness, having three generations of OFA clearances on both sides of the pedigree will guarantee that the litter will be free of hip dysplasia.

3. Sending radiographs in to OFA at the end of a calendar quarter will increase the chances that your dog will get a clearance because the reviewers need to meet their quota.

4. Upon reviewing your dog's hip X-ray with your veterinarian, you feel it may not pass OFA evaluation. It is a good idea to wait 6-8 months, x-ray again, and submit because your dog will be older and the chances of getting an OFA clearance will be higher.

5. It is a bad idea to submit preliminary radiographs before your dog is 2 years old because OFA will compare both radiographs and lower your dog's rating one level.

6. OFA will not certify your dog to be clear of hip dysplasia until he is radiographed at 24 months of age or older.

7. It is a good idea to refrain from sending in a marginal radiograph because if your dog does not get an OFA number, this information may be released to the national breed club.

8. Dietary supplementation with (e.g.) Vitamin C, cottage cheese, and calcium will not prevent hip dysplasia.

9. Administering anesthesia to a dog when radiographing his hips will cause additional subluxation in the hip joint, and therefore, make the dog look more dysplastic than he really is.

10. It is a bad idea to radiograph a bitch in season, because of the additional laxity in her joints during estrus.

11. It is a good idea not to rd breeding stock because the amount of radiation exposure will render the dog sterile.

12. Although there is no cure for hip dysplasia, there are medical procedures which can be performed to alleviate pain and enable the dog to live a comfortable life.

13. A dog that has been diagnosed radiographically as having severe dysplasia will always show overt symptoms in (e.g.) gait and pain.

14. A dog that exhibits no overt symptoms can be presumed to be free of hip dysplasia, and therefore, does not need to be radiographed.

15. OFA's panel of radiologists agree over 90% of the time that a dog is either within normal limits or dysplastic.

16. A dog that shows dysplasia in only one hip will still receive an OFA clearance.

17. The OFA must fail a certain percentage of radiographs it receives in order to maintain its standard.

18. Severely restricting your dog's physical activity during the first two years of life will not guarantee that is hips will be free of dysplasia.

19. It has been proven scientifically that hip dysplasia is genetically inherited.

20. When considering the extent of OFA soundness in a potential stud dog, knowledge of the incidence of hip dysplasia of his littermates is very important. Knowledge of the incidence of hip dysplasia of his progeny as well will indicate his potential as a superior sire.

Remember, the ultimate goal in control of a polygenic trait is to use breeding stock with pedigree depth for the desired trait.


ANSWERS

The answers to last issue's OFA IQ test are here. All answers have been developed in consultation with Dr. E. Al Corley, Project Director of OFA, and all supporting quotations have been taken (with Dr Corley's approval) from the pages noted in parenthesis from his 1989 monograph on hip dysplasia: Hip Dysplasia: A Guide for Dog Breeders and Owners, co-authored with G.G. Keller. Copies of this may be obtained from OFA for $5.00.

I would like to publicly thank Dr. Corley for all he has done to help get the new GRCA OFA program off to a great start, for his advice on developing answers to this test and for being a continuing source of inspiration for me in my own personal search for excellence.

1. FALSE The key word here is guaranteed. "Normals mated with normals produce more normals than matings of two dysplastics or a normal with a dysplastic. The appearance (phenotype) of the hips ranges from excellent to severely dysplastic with all degrees between the extremes." (pg 5)

2. FALSE Again, the key word is guaranteed. "The following paraphrased breeding criteria have been demonstrated to more rapidly and effectively reduce the frequency of dysplasia: (a) breed only normal dogs to normal dogs, (b) the normal dogs should come from normal parents and grandparents, (c) the normal dogs should have over 75% normal siblings, (d) choose a sire that has a record of producing normal progeny that exceeds the breed average, and (e) choose replacement bitches that have better hip joint conformation than their parents and the breed average." (pgs 6-7)

3. FALSE OFA readers do not operate within any kind of a quota system and the final evaluation of a radiograph is not established until after all three radiologists have logged their reading and turned it over to the OFA. "The radiographs are forwarded to the fist radiologist in groups (log) of 50. When the first evaluation is complete, the log is sent to the second radiologist and the cycle is repeated until the third radiologist returns the log. Each evaluation is independent - that is, no radiologist knows what interpretation was given by another." (page 14)

4. TRUE This is a very tricky question! In trying this test on his own staff, Dr. Corley's staff commented that the question needed to be reworded to state the point correctly. It is true that "OFA Classifications are based on comparisons among other individuals of the same breed and age..." (pg 15), and it is also true that an older Golden would be judged according to a different set of criteria than a two-year-old. However, it is not a good idea to wait to submit your radiograph in the hope that the condition of your dog's hips will remain exactly the same, until enough time has passed that the criteria against which he is evaluated is relaxed to the point where the hips will pass. The genotype of the dog is still what it is, and will still be passed down to the progeny. What you will end up with is a dog that, although he may be cleared himself, will produce a greater percentage of dysplastic get.

5. FALSE "Preliminary evaluations of the hip status are provided on any agedog. The evaluation is done by one veterinary radiologist, the OFA Project Director. Radiographs of dogs 24 months of age or older are independently evaluated by three veterinary radiologists. There is an amazingly high agreement among the radiologists. All three agree on the diagnosis of normal, borderline, or dysplasia in approximately 94% of the cases. All three agree on the specific phenotypic rating in approximately 80% of the cases. Comparison of the preliminary evaluation with the final OFA evaluation at 24 months of age or older reveals approximately a 90% reliability factor." (pg 25)
This means that the evaluation of one person compared against the combined evaluation of three people a year or more later resulted in the same determination 90% of the time. In addition, this means that the three reviewers agreed among themselves as to the exact phenotypic rating 80% of the time. In the 20% of cases where all three radiologists did not agree on the specific phenotypic rating, "Two evaluations of the same phenotype result in a consensus of that phenotype; three different evaluations (i.e., excellent, good, and fair) results in a consensus of the middle phenotype." (pg 14) This procedure precludes the possibility of a dog's rating could be "knocked down a notch" because of the independence by which the ratings are developed.

6. TRUE "Only dogs that are 24 months of age or older at the time of radiography can qualify for an OFA breed registry number. The hip joint status of younger dogs will be evaluated, but a consultation report will be issued." (pg 12)

7. FALSE "If and OFA Registry number is assigned (excellent, good, or fair) the information is released to the breed clubs. If the consensus was borderline or dysplastic, the information is given only to the owner and the veterinarian. (pg 25)

8. TRUE A number of dietary items, such as megadoses of Vitamin C, supplementation with selenium, etc., periodically appear in the popular press as preventatives or treatments for CHD. None of these anecdotal reports have been shown to be effective. On the contrary, megadoses of anything are usually harmful." (pg 22)

9. FALSE The key words here are "make the dog look more dysplastic than he really is" versus "appears to give a truer evaluation of the hip status." Preliminary data indicates that chemical restraint does affect the radiographic appearance of the hip joints in some dogs. Current information, observations made on large numbers of dogs supports the recommendation that chemical restraint (tranquilization to the point of relaxation or general anesthesia) be used. This appears to give a truer evaluation of the hip status, but more research is needed on this controversial subject, as there is an absence of controlled scientific data." (pg 11)

10. TRUE "Estrus appears to affect the reliability of diagnosis in some bitches. Some bitches in season demonstrate a degree of subluxation that is not present when the bitch is out of season. Radiography of these bitches may result in a false diagnosis of CHD. It is recommended that bitches not be examined for CHD when in season. Currently studies are underway to define this observation. Hopefully, these studies will also define the time before and after estrus that radiography can be done without obtaining a false diagnosis. (pg 11)

11. FALSE "Proper collimation and protection of attendants is the responsibility of the veterinarian. Gonadal shielding is recommended for male dogs. Radiography of bitches in season or pregnant should be avoided. (pg 13)

12. TRUE Treatment for relieving pain and improving function includes giving aspirin or one of the newer synthetic aspirin products used in the treatment of degenerative bone disease. Surgical procedures include: 1) removal of the femoral head(s), and (2) division of the pectineus muscle. These procedures may relieve pain and improve function in some individuals.

13. FALSE "There is little correlation of the radiographic findings with the clinical signs. For example, a dog with mild radiographic changes may be crippled, whereas a dog with severe radiographic changes may not present any clinical signs. (pg 26)

14. FALSE "CHD cannot be diagnosed by observing how the dog moves, acts, lies down, etc. The clinical signs may be caused by other problems; therefore, a complete orthopedic and radiographic examination is required before arriving at the conclusion that the signs are caused by CHD." (pg 7)

15. TRUE See the answer to question 5 above.

16. FALSE "Hip dysplasia may occur in only one hip (unilateral). In the dog, normal hips are not bilaterally symmetrical and which hip tends to be more shallow (left or right) appears to be breed dependent. Evidence of unilateral dysplasia follows the same pattern. That is; unilateral hip dysplasia is breed dependent. It occurs more frequently in the left hip of the Labrador Retriever, Newfoundland, Akita, and Golden Retriever, but more frequently in the right hip of the Rottweiler. (pg 11) Normal hips are not bilaterally symmetrical. One hip usually has a shallower acetabulum than the other. Evaluation of the phenotypic hip status is based on the appearance of the shallower hip." (pg 23)

17. FALSE One of the objectives of OFA is, "To advise, encourage, and establish control programs to lower the incidence of orthopedic disease." There is no quota system, nor any other type of standard percentage that must be maintained. Table I shows the percentage distribution of excellents, goods, and fairs, borderlines, milds, moderates, and severes for all breeds (with 100 or more OFA submissions) from january 1974 to March 1989. Table II ranks those breeds from the highest to the lowest percentage of dysplastics. (NOTE: St Bernards are Number One with 47.4% of 1027 submissions evaluated dysplastic; Borzois are tied for last place with 2.4% of 394 submissions dysplastic. Goldens are Number Fifteen, with 23.8% of 35,532 submissions dysplastic.)

18. TRUE "Environmental factors include all external factors that may affect how the hip joint develops, i.e., in utero health of the fetus, nutrition, illness, trauma, exposure to chemicals, etc. No environmental factor has been shown to cause CHD, but the environment can affect the genetic expression of CHD. For example, a higher than optimum caloric intake during the rapid growth phase may exacerbate the radiographic changes and/or clinical symptoms of CHD." (pg 21)

"Heritability indexes are purported to measure, on a scale of 0% to 100%, how much of the phenotypic variation in a studied population is of genetic origin. Genetic selection for or against any trait is expected to yield poor results if the heritability index is low (10%). When the index is moderate (20% to 40%), selection based on individual phenotypes is expected to yield slow yet substantial results, but more rapid results can be obtained if phenotypes of the relatives is also considered. The most rapid results are obtained when the index is high (40% to 100%), as the individual phenotype becomes a good predictor of the genotype. Results of selective breeding practices indicates that the dysplastic trait should be considered in the moderate to high category. Unfortunately, many breeders and veterinarians misinterpret the meaning and use of heritability estimates. For example: a calculated value of 50% means that 50% of the variation in phenotypes in the studied population is controlled by the genes. This does not mean that 50% of dysplastic dogs are of a genetic cause. Nor does it mean that 50% of the changes in an individual dog are caused by the genes and the remaining 50% by the environment. (pg 6)
"In dysplastic dogs, the hip joint is a weakened structure that is more subject to being injured by normal activity such as jumping off a couch, or rough housing with a playmate. Frequently, this results in acute lameness that in the mind of the owner was caused by the injury, whereas the underlying dysplasia actually made the joint more susceptible to injury." (pg 7)

19. TRUE Hip dysplasia is an inherited trait and it is controlled by the genetic makeup (genotype) of the individual dog. The genotype is determined by the genes received from the parents; one-half from the sire and one-half from the dam. From the first to the last published scientific report, veterinary scientists have agreed that there is a genetic basis for hip dysplasia. The literature contains differences in concepts of the mode of inheritance. Regardless of changes in the concepts of the mode of inheritance, or how the genes exert their influence, scientists have repeatedly demonstrated that hip dysplasia is controllable by selective breeding." (pg 4)

20. TRUE "A dog with excellent hips but with more than 25% of its brothers and sisters being dysplastic is a poorer breeding prospect than a dog with fair hips and less than 25% of its brothers and sisters being dysplastic." (pg 7)