Traditional methods of evaluating dogs for hip dysplasia risk may miss 80 percent of cases, according to a new study.
Hip dysplasia is a painful joint disease that can cause limping and soreness. As the disease develops, the dog may be unable to walk on its own. Large breeds are at higher risk for hip dysplasia, perhaps because their joints bear more weight.
Because hip dysplasia is inherited, purebreds, with their limited gene pool, are also at higher risk for the disease than mutts. Reputable breeders get their dogs checked for hip dysplasia risk before mating them, but the new study casts doubt on the current methods for evaluating that risk.
"We believe many veterinarians are not using the best test to control a disease," University of Pennsylvania veterinary surgeon Gail Smith, who led the study, said in a statement. "In many ways, this is an animal-welfare issue."
Evaluating hips
The study pitted the traditional method of evaluating a potential breeding dog with a method patented by the University of Pennsylvania called PennHIP. In both methods, X-rays of the dogs' hips are analyzed for arthritis and laxity, or looseness, of the joints. The looser the joints, the higher the risk of later dysplasia.
PennHIP uses different X-ray viewpoints than the traditional method, allowing veterinarians to predict later arthritis and hip dysplasia in puppies as young as 16 weeks. Previous studies have shown the PennHIP to be very reliable, the researchers said.
The current study examined 439 dogs, many of which were dysplasia-prone breeds like German shepherds, Labrador retrievers, golden retrievers and Rottweilers. All of the dogs that scored as having dysplasia by traditional metrics were also found to have dysplasia according to PennHIP.
But 52 percent of dogs whose hips would score an "excellent" rating using traditional methods were in the at-risk category according to PennHIP. Similarly, 82 percent of "good" hips and 94 percent of "fair" hips were judged at-risk using the new method.
Fighting hip dysplasia
Accurately pinpointing hip dysplasia risk is important, because symptoms usually develop later in life, after dogs have had puppies. If veterinarians continue to miss at-risk dogs, breeders will continue to match dogs with dysplasia, and their puppies will suffer, according to the researchers. Despite current hip-screening programs, studies have not found a significant decrease in canine hip dysplasia worldwide.
The PennHIP method, which Smith invented, has already been adopted by many guide-dog schools, as well as the U.S. Air Force and the U.S. Army.
Eventually, the researchers said, PennHIP could be applied to humans. Hip arthritis is similar in both dogs and people, and preventative methods like weight loss can ease the pain in both species. If researchers can accurately predict later arthritis in puppies, they may be able to do the same in children.
"In humans, with appropriate studies of course, it is conceivable that mothers of susceptible children — and there are many — may adjust a child's lifestyle, including diet, to delay the onset or lessen the severity of this genetic condition," Smith said.
The research is detailed in the Sept. 1 issue of the Journal of the American Veterinary Medical Association.
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