THE PATHOGENESIS AND DIAGNOSIS OF CANINE HIP-DYSPLASIA - A REVIEW

Hip dysplasia is a common developmental problem affecting the canine p opulation. Despite extensive research into the condition, many questio ns remain unanswered and numerous misconceptions are present among the general public. The purpose of this paper is to review the current kn owledge on the development of hip dysplasia, factors modifying its dev elopment, and current diagnostic techniques. A computerized literature search was conducted for the period of January 1983 to April 1985 usi ng the MEDLINE and CAB databases, and the keywords hip dysplasia, hip, dog, and canine. Other articles, wherever possible original research articles, published before 1983 were also reviewed. Animals affected b y hip dysplasia are born with normal hips, but quickly develop subluxa tion of the femoral head. Degenerative joint disease follows. Hip dysp lasia is a complex, inherited, polygenic trait. Selective breeding of only normal dogs with normal littermates, parents, and grandparents is the recommended method of reducing the incidence in the general popul ation. Gene expression in affected individuals may be modified by a nu mber of environmental factors. These factors do not cause hip dysplasi a, but they alter manifestations of the trait and its severity. Nutrit ion is a major environmental factor. Excess energy consumption increas es the frequency and severity of hip dysplasia in genetically predispo sed dogs. Food intake should be regulated to maintain a slender figure with the ribs and dorsal vertebral spines easily palpable, but not vi sible. Excess dietary calcium and vitamin D contribute to hip dysplasi a In genetically predisposed individuals and should be avoided. High d ose vitamin C supplementation in growing puppies does not prevent hip dysplasia, and this practice should be discontinued. Animals must be 2 years old before they can be certified as normal, but the disease may be diagnosed earlier. Earlier diagnosis of the condition would be ver y useful for the selection of breeding stock, but palpation techniques and the standard extended view radiographs have unacceptably high rat es of error in young puppies. Stress radiography techniques may improv e the accuracy of early diagnosis in the future.