Trends in hip dysplasia control: analysis of radiographs submitted to the Orthopedic Foundation for Animals, 1974 to 1984

From 1974 through 1984, the Orthopedic Foundation for Animals evaluated 143,218 radiographic submissions representing 151 breeds of dogs. All breeds from which there were 35 or more evaluations had some frequency of dysplasia. Seventy breeds, each with over 100 submissions, were tabulated and ranked according to frequency of hip dysplasia. Frequency of dysplasia varied from 0.6% in the Borzoi to 46.9% in the Saint Bernard. These data were compared with data obtained earlier (1966 to 1973) on evaluations in 38 breeds for changes in frequency. There was significant (P less than 0.05) reduction in frequency of dysplasia in 27 breeds, a significant (P less than 0.05) increase in frequency in only 1 breed (German Shorthaired Pointer), and no significant change in frequency in 10 breeds. The median significant decrease was 22.4%, and the range was from 3.1% in the Chesapeake Bay Retriever to 48.7% in the Keeshond. The reduction in frequency of hip dysplasia demonstrated the value of a control program. There were 5 breeds with a significant (P less than 0.05) decrease in frequency of dysplasia that had over 5,000 evaluations from 1974 to 1984. The decreases in frequency were independent of changes in American Kennel Club registrations for these breeds (a dramatic decline in registrations for the German Shepherd Dog and Old English Sheepdog, and a dramatic increase for the Rottweiler, Golden Retriever, and Labrador Retriever). Frequency regressed linearly in the German Shepherd Dog and Old English Sheepdog, but regressed nonlinearly in the other 3 breeds. The percentage reduction in frequency from the base frequency (1966 to 1973) for these breeds was 17.5% for the German Shepherd Dog, 23.1% for the Old English Sheepdog, 9.1% for the Rottweiler, 10.1% for the Golden Retriever, and 6.8% for the Labrador Retriever.