Hip laxity solid predictor of animal arthritis

Philadelphia-University of Pennsylvania (UP) veterinarians saythey have a solid predictor, in any species, of future arthritis.

Lead reasearcher Dr. Gail K. Smith, professor of orthopedic surgery andchair of the Philidelphia Departent of Clinical Studies at UP's veterinaryschool, says the conclusion was taken from an international database of16,000 dogs. The scientists say that laxity in the hip joint-several millimeters'worth of excessive play between the ball of the femur and the hip's socket-correlatesstrongly with the advent of hip arthritis later in a dog's life.

"The relationship between hip laxity and arthritis in dogs is akinto the relationship between high cholesterol and heart disease in humans,"Smith explains. "Hip laxity is no guarantee of arthritis later in life,but it is a very solid risk factor."

It is hoped this finding could lead to new ways of averting or minimizingthe occurrence of canine arthritis, which afflicts an estimated 70 to 80percent of dogs in certain breeds. Since a canine generation is just 30-36months, Smith says selective breeding to avoid high-laxity individual animalscould slash the incidence of canine arthritis within 10 years.

The research was published by the Journal of the American VeterinaryMedical Association (Dec. 15).

Smith began collecting data on arthritis in dogs in 1983. "Degenerativejoint disease is phenomenally prevalent in dogs. This work will allow breedersand pet owners to make informed decisions to help control and possibly eradicatethe disease," Smith adds.

This study grew out of Smith's development of a licensed system calledthe PennHip Improvement Program. The system is used to measure hip laxityamong dogs. About 1,400 veterinarians, trained in this system, providedthe source of the data used for the study.

PennHip positions dogs differently than traditional radiography of thehip, which images dogs with rear legs extended. With this system, the veterinariantakes one image of a sedated dog's hip in the conventional position. Then,with the hips in a more neutral position, this image is supplemented withtwo others: one with the femoral head pushed in toward the hip socket andone with it pulled away from the socket. Comparing the latter images letsclinicians determine how many millimeters of play exist between femur andsocket, the university explains.

The university remains the central repository for images collected usingPennHip, allowing for population studies of this size. The number of dogsprofiled in the database is growing by 3,000 a year.