Patti Widick Neale
September 1998*

Canine hip dysplasia is a common orthopedic affliction that has been seen in nearly all breeds of dogs, though it affects medium to large dogs with greater frequency than the smaller breeds. Many fanciers are of the impression that Borzoi, and sighthounds in general, are not affected by hip dysplasia. This "common knowledge" has been passed on by breeders and exhibitors to such an extent that the fancy has been lulled into a complacency that is not healthy for the breed. The truth is, there are dysplastic Borzoi.

What is hip dysplasia?

The Merriam-Webster dictionary definition of dysplasia is: abnormal growth or development (as of organs or cells); broadly: abnormal anatomic structure due to such growth. Hip dysplasia is a heritable disease affecting the coxofemoral joint, first recognized in dogs in the 1930s.

In a normal dog the head of the femur is deeply seated into the hip socket, held in place by ligaments, the joint capsule, and the surrounding musculature. Though a puppy is born with normal hip joints, they are composed of cartilage, which is a rather pliable tissue. For the two surfaces of the ball and socket of the hip joint to continue to develop together in a smooth, mechanical alignment they must remain in close contact.

A dog that possesses the genes for hip dysplasia develops a looseness or laxity in the structures that hold the ball in the socket. Due to the resulting space between the two surfaces, both the head of the femur and the acetabulum will develop and wear unevenly. As the abnormal pressures on the joint continue, both bones will compensate by thickening or scarring in some areas and wearing away in others, a process called remodeling. The femoral head is forced further out of the socket (subluxation), which becomes increasingly shallow from the arthritic changes. This vicious cycle progressively destroys the joint over time, which results in pain and lameness for the dog.

Environmental conditions can influence both the rate of progression and the degree of degeneration of the hip joint. Particularly in large, fast-growing breeds, skeletal growth and muscle development are not well matched. Puppies that carry more weight than average for their breed and age, have been shown to manifest the signs of dysplasia sooner than their lighter littermates by placing an additional strain on muscles that already are not keeping pace with rapid bone growth. Forced exercise, constant slippery footing, and over-supplementation may exacerbate the signs of hip dysplasia but these factors are not the cause of the affliction. The genetic tendency toward joint laxity always precedes the accelerating environmental factors.

The Orthopedic Foundation for Animals (OFA) and the University of Pennsylvania (PennHIP), have developed standard evaluation procedures for evaluating hip conformation, and both maintain registries of radiographs submitted for assessment by their trained analysts. OFA statistics are the focus of this article.

The origin of the myth

Borzoi have received OFA numbers at the average rate of just over 20 dogs per year for the 24 years that OFA records are available. In the first ten years, the per-year rate was 26 dogs per year, indicating that few Borzoi owners thought their breed likely to need testing. Borzoi are a large, fast-growing breed, so by that criterion, they should not be immune to disease that has been seen in all other large and giant breeds. So how did the myth begin?

In the early 1970s, a study was done on the relationship of muscle mass to hip dysplasia. Three breeds were used; German Shepherd Dogs, a type of Foxhound called July Hounds, and American Greyhounds, a breed in which hip dysplasia was unreported, and which have as much as 50 percent more pelvic muscle mass than breeds that commonly have dysplasia. The greyhounds were all racing-bred dogs; no show-bred Greyhounds were used. The results of the study indicated that large pelvic and thigh muscles go together with good hips.

A report of that study was part of a book called Canine Hip Dysplasia and How to Control It written by Drs. Wayne H. Riser and Harry Miller, under the auspices of the OFA. It was the definitive piece on hip dysplasia available to the dog-owning public, at a time when awareness of the disease within the fancy was in its infancy.

Greyhounds did not have hip dysplasia. Greyhounds were sighthounds. Borzoi were sighthounds and built similarly to Greyhounds. It was an easy error in logic to assume that Borzoi did not have hip dysplasia as well. The OFA statistics for the few Borzoi radiographs submitted prior to 1984 bore that out with a dysplasia rate prior to 1984 of just 0.6% or 2 dysplastic submissions during that period. So Borzoi breeders could feel safe in the knowledge that their breed was exempt. Average yearly submissions declined.

But racing Greyhounds are a unique breed. Their tremendous genetic muscularity is unparalleled among large breeds. They have been selected for one thing, pure speed on the flat, for 90 years in this country. Any track Greyhound with bad hips (read slow) isn't allowed to live long enough to reproduce the problem so the speed criterion has effectively eliminated dysplasia. The economic reality of the racing industry eliminates testing. Only 14 Greyhounds received OFA numbers before 1984 so the small Greyhound fancy wasn't adding much data either.

The OFA record

The Orthopedic Foundation for Animals is a voluntary, semi-closed registry. It is voluntary, since the owner of a dog decides whether or not to submit a given radiograph of their dog's hips, good or bad, to the OFA. Dogs with hip conformation in the normal range, are assigned a sequential number within their own breed. It is a semi-closed registry, in that the records of dogs who fail to receive a normal hip rating are not available to the public. This limits its usefulness as a tool to select genetically sound breeding stocks as affected relatives of cleared individuals cannot be identified.

The problem with a voluntary registry is that OFA statistics are heavily weighted on the side of normalcy. This means that dysplasia is under-reported, as much as 2-3 times the OFA figures, according to a survey done at the University of Pennsylvania's Veterinary Hospital. The owner's veterinarian makes a preliminary assessment of the x-ray, and tells the owner if the hip conformation is or is not likely to pass or fail. The evaluation fee is sent with the film to OFA, and there are mailing costs involved as well as paperwork. If an owner believes his dog is unlikely to pass, he is already discouraged with the bad news and in many cases will not bother to complete the submission process without other incentive.

It is the OFA's position that this prescreening process affects all breeds in a similar manner. If that were the case, then one could use the Borzoi's negligible reported incidence of affected dogs compared to other breeds, to conclude that HD in Borzoi is virtually nonexistent. But there are a number of factors that create significant differences between breeds in the number of radiographic submissions, both qualitative and quantitative.

What's the difference?

Many parent clubs, in breeds that have had a high incidence of HD, have ongoing programs to increase awareness of the disease, and codes of ethics for their members that require testing of breeding stock. Though no breeder can be forced to comply, the most effective method of encouraging compliance used in many of the Working, Herding, and Sporting breeds, is the restriction of advertising in the club publications to dogs that have hip (and often other health) clearances, and to puppies with two cleared parents.

Other breed clubs use education and peer pressure so effectively that no fancier would consider breeding a bitch or using a stud dog without an OFA number. The educated puppy buyer expects their puppy's parents to have OFA numbers as well.

In some of the rare breeds, where the spirit of cooperation among fanciers for genetic testing could be critical to survival of the breed, nearly all breeding animals are tested, as well as littermates, and the resulting information is shared for the good of the fancy.

Each of these factors create social and economic incentive to breed only from OFA'd animals. The need to have an OFA number provides greater impetus for the owner to submit any x-ray, not just the ones their own veterinarian is certain will pass, hoping for at least an OFA Fair rating. Without an OFA number, even a Fair rating, their dogs and puppies will be far less marketable. Because of this economic and peer pressure in certain breeds, a greater number of films are submitted and a higher percentage of dysplasia is reported.

Borzoi breeders have had no such incentives, either to x-ray in the first place, or further, to submit questionable films. Therefore, the 20 or so OFA submissions, in a breed where there are more than 1200 dogs born each year, makes the OFA record statistically useless as a measure of HD in Borzoi.

In a three-year period, 1992 through 1994, only 75 Borzoi received OFA numbers. Of that number, 26 Borzoi, more than one third, were from the same kennel, one with a fairly isolated gene pool. From all appearances, most or all Borzoi within this kennel's litters were x-rayed. This is admirable for the kennel and is good science; testing all littermates is the most effective testing method for identifying and eliminating an undesirable trait. However, with this kennel's contribution to the database removed, the average number of other Borzoi certified in each of those three years was only 12, which reduces the significance of the stats to the breed at large to nothing more than a curiosity.

Several other sighthound breeds have a higher incidence of hip dysplasia than Borzoi, notably Afghan Hounds, but Irish Wolfhounds, Ibizan Hounds and Salukis and now even Greyhounds are also listed, which further erodes the supposition of sighthound immunity to hip dysplasia. Because of the low number of dogs tested in the latter four breeds, the significance of their OFA record is similar to that of Borzoi. Among sighthound breeds, only the Afghan Hound approaches statistical relevancy.

The truth is, there are dysplastic Borzoi. While it can hardly be considered a major breed problem, denying its existence based on the limited OFA data available is foolhardy. To paraphrase a famous saying, the price of freedom from genetic diseases is eternal vigilance.

What can be done?

For the OFA data to have any significance for Borzoi, so that there is a realistic assessment of the occurrence of HD within the breed, there needs to be a large number of dogs x-rayed, and the resultant films, both those that look good, and those that look questionable, sent in to become part of the OFA database.

The price structure for OFA hip or elbow certification favors submitting multiple films for evaluation at the same time. The cost for one dog is $30.00, or $75.00 for a group of three or more littermates. Five or more submissions of dogs owned or co-owned by the same person brings the cost down to $15.00 each, or half-price, when sumitted in a batch. Breeders with co-owned dogs could get together and send their films (with forms supplied by their own veterinarians) in a group to take advantage of the reduced fees. In that way, the economic impact of submitting all films, not just the best ones, would be minimized, and the Borzoi fancy as a whole would benefit from the resulting increase in the accuracy of the information.

The OFA will accept obviously dysplastic radiographs without a fee, for inclusion in their database.

About the data

Prior to 1974 an OFA number could be assigned to dogs assessed at twelve months or older. Studies found the accuracy of the readings was improved to above 95% on a more mature skeleton, so since 1974, 24 months has been the minimum age for issuance of a permanent rating. The record of Borzoi OFA numbers starts with number 118. The previous numbers were assigned before OFA started using a computer in 1974 and OFA does not have those old records in its database.

From 1974 until 1987 the only notation about hips that met OFA's criteria was "normal". Beginning in 1987 normal hips were further designated "fair", "good", and "excellent".

The OFA number is made up of several parts. The first letters, "BZ" indicates the breed, followed by the sequential number of certification within that breed. The next letter, E, G or F, is quality rating for normal hip conformation: excellent, good or fair, followed by the age in months at which the dog was evaluated. M or F stands for male or female, and if followed by a T, indicates that the dog was tattooed.

For the last few years, AKC has included OFA numbers of individual dogs and their parents on registration forms and in certified pedigrees if the dog has been rated at the time of registration. As of July 1, 1996, AKC only accepts OFA evaluation results for dogs that are positively and permanently identified at the time of testing, usually by tattoo or microchip so the dogs reported in the Gazette each quarter may not reflect all that have been cleared.

 * OFA fee structure for this article was updated November 2003

* In the last 10 years, submissions of Borzoi have averaged 24 per year. At least two affected (dysplastic) radiographs have been submitted.