A recent study to evaluate the likelihood a dog will develop hip dysplasia indicates the standard OFA (Orthopedic Foundation for Animals) scoring method may be missing the mark by a large margin.
The study, conducted by the University of Pennsylvania, involved 439 dogs older than two years, many of which were breeds commonly susceptible to hip dysplasia, including:
- German Shepherds
- Labrador Retrievers
- Golden Retrievers
In a comparison of the traditional OFA and newer PennHIP (Pennsylvania Hip Improvement Program) scoring methods, results showed 80 percent of dogs scored as ‘normal’ by OFA are actually at risk for developing osteoarthritis and hip dysplasia according to their PennHIP ratings.
OFA scores are used to certify dogs for breeding purposes; testing is typically done around the age of two.
The primary differences in the two screening methods involve the positions in which a dog’s hip is x-rayed, and more precise scoring in the case of the PennHIP test. The OFA method uses conventional hip-extended x-rays; the PennHIP method adds a small distraction force, which reveals additional joint laxity of the type that is known to be directly linked to the development of osteoarthritis.
“According to the OFA's Dr. G.G. Keller, director of veterinary services, that assertion misses the mark." (The study) is comparing apples to oranges because the OFA method is not designed to measure joint laxity. They are different methodologies," he says, adding that joint laxity is not the only factor to consider in evaluating susceptibility for developing hip dysplasia.”
The results of the University of Pennsylvania study indicate over half of the dogs’ hips rated ‘excellent,’ 82 percent of those rated ‘good,’ and 94 percent scored ‘fair’ by OFA standards were susceptible to canine hip dysplasia (CHD) according to their PennHIP ratings.
The only area of agreement between the two methods was for dogs with hips OFA scored as ‘dysplastic.’
According to researchers, even if only those dogs with OFA-rated ‘excellent’ hips were bred, from over half to 100 percent of the puppies, depending on breed, would be susceptible to hip dysplasia based on the PennHIP method.
The Penn researchers warn that if breeders continue to breed dogs based on traditional OFA scoring they will continue to mate dogs susceptible to dysplasia, and the hip quality of future generations of dogs will fail to improve.
Dr. Gail Smith, professor of orthopedic surgery and inventor of the PennHIP method, says despite well intentioned hip-screening programs to reduce the frequency of the disease, little progress has been made because CHD is erroneously considered an ‘all or nothing’ disease—the pet either has it or it doesn't.
According to Dr. Smith, the advantage of the PennHIP radiographic method is its ability to determine not only which dogs are immediately susceptible, but which are at risk to develop a problem later in life. "We have to put aside the 'all or nothing' notion. There is a variable degree of susceptibility for the disease," he explains.