New hope for old hips
Osteoarthritis is a common, often-debilitating disease of both animals and humans. It may involve any joint, but the joints most clinically affected are the hip, elbow, shoulder, knee, and spine. It is estimated that one in five dogs will show obvious signs of pain from osteoarthritis; in many more dogs, however, the signs will be subtle or subclinical. In dogs, the most common form of osteoarthritis is canine hip dysplasia. The radiographic prevalence of canine hip dysplasia is as high as 75% in some breeds and the disease can cause pain and dysfunction in affected animals. Most types of osteoarthritis, including canine hip dysplasia, are thought to be developmental diseases having complex inheritance, so-called polygenic diseases. It is understood that the incidence and severity of such genetic diseases can be influenced considerably by environmental factors,1-4 meaning any nongenetic factor, such as diet, lifestyle, housing, or trauma. In the past 15 years, landmark collaborative investigations have been conducted at the Nestlé Purina laboratories in St. Louis, Missouri, demonstrating the power and utility of environmental manipulation to offset or prevent a genetic predisposition to disease. These studies evaluated the effect of food restriction on development of hip joint laxity during growth and subsequent occurrence of osteoarthritis in joints during adulthood. Although not all results have yet been published, this lifelong investigation in a cohort of 48 Labrador retrievers is unique and represents our best understanding of the natural course of joint osteoarthritis, and especially canine hip dysplasia.5-7 The most recent unpublished study is presented below in abstract form.
ABSTRACT (UNPUBLISHED DATA):
Influence of Restricted Feeding and Age on Hip Osteoarthritis and Hip Score: A Life-long Study in Labrador RetrieversSmith GK, 1 Power MY,1 Biery DN,1 Evans RH,2 McKelvie P, 1 Shofer FS,1 Gregor TP,1 Ballam JM,3 Mantz SL,3 Lust G,4 Houlton JEF,5 Lawler DF,3 Kealy RD3
1Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania; 2Veterinary Pathology Services, Aliso Viejo, California; 3Nestlé Purina Research, St. Louis, Missouri; 4James A. Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, New York; 5Davies White Veterinary Specialists, Higham Gobion, Herts, England
There has been slow progress in reducing the incidence of canine hip dysplasia by selective breeding of normal dogs.8 The conventional diagnosis of canine hip dysplasia has been based on subjective radiographic findings of subluxation of the coxofemoral joint, or secondary osteoarthritis as seen on evaluation of the hip-extended, ventrodorsal radiographic view of the pelvis. In the United States this analysis is performed by the Orthopedic Foundation for Animals (OFA) scoring system after dogs are 2 years of age. In much of Europe a similar analysis is made after 1 year of age. Excessive hip laxity (Norberg angle measured from the hip-extended radiograph) can be marginally reduced by limiting caloric intake and this tightening of the joint prevents or delays the expression of osteoarthritis in some dogs predisposed to the condition.5-7 It has been generally assumed that the subjective scoring of hip phenotype at 1 or 2 years of age accurately reflects the true hip phenotype of the dog. No lifelong studies have been conducted to document the accuracy of the one- or two-year evaluation to predict the end-of-life hip phenotype. The purpose of the present investigation was to test the influence of food restriction on hip phenotype and to compare early hip screening (OFA and PennHIP scores at 2 years of age, and the British Veterinary Association/Kennel Club [BVA/KC] scores at 1 year of age) with end-of-life hip phenotype (radiographic osteoarthritis, OFA score, and histopathologic osteoarthritis).