Hip dysplasia is one of the most common skeletal diseases seen in dog (1 out of 3 large breed dogs may have the disease) causing pain, stiffness and affecting overall quality of life. During hip dysplasia, the joints that formed the hip are not tight together creating an area of continuous wear and friction. This leads to arthritis and chronic joint disease.
Although there is not complete cure for some dogs, there are many options to alleviate the clinical signs and the progression of the disease. The aim of treatment is to enhance quality of life. But early diagnosis is fundamental. PennHip evaluation was developed for this purpose.
In the 1980’s, researchers at the University of Pennsylvania’s School of Veterinary Medicine pioneered a way to assess hip laxity. The hip joint is a ball-and-socket joint, with the ball of the femur (femoral head) fitting into the hip socket (acetabulum). Hip laxity refers to the degree of “looseness” of the hip joint made by the femur and the hip socket. Studies have shown that dogs with looser hips (excessive hip laxity) are at higher risk to develop hip dysplasia than dogs with tighter hips (minimal hip laxity).
PennHipp can identify, as early as 16 weeks of age, dogs that are susceptible to developing hip dysplasia. This offers breeders the opportunity to make early decisions on breeding stock, and allows veterinarians to advise pet owners on lifestyle adjustments and preventive strategies to minimize the pain and progression of the disease.
The dog is positioned on the X-ray table with hips in a neutral orientation and a custom distraction device is used to reveal the maximum amount of hip laxity. To achieve this, the dog's muscles are completely relaxed by the used of a sedative or general anesthesia. Three X-rays are then performed and submitted for evaluation and distraction index.
Distraction Index (DI)
The DI is an indication of the percent out of joint of the hip joint and therefore, it measures hip laxity—the inherent distance the ball can be displaced (distracted) from the hip socket. This is expressed as a number between zero and one. A DI near zero indicates little joint laxity (very tight hips). A DI closer to 1.0 indicates a high degree of laxity (very loose hips). Dogs with tighter hips are less likely to develop hip dysplasia than dogs with looser hips. So a DI of 0.15 means the femoral head is 15 percent out of joint (a tight hip), and a DI of 0.77 means the head is 77 percent out of joint (a pretty loose hip). A threshold level of 0.30 has been identified, below which hip dysplasia is very unlikely to occur.
For pet owners
If your dog is identified to be at risk for hip dysplasia at an early age, appropriate strategies (diet, medication, and/or activities) to delay or diminish the ultimate course of the disease or surgery can be made.
Breeders can reduce the incidence and severity of Canine Hip Dysplasia (CHD) in future generations of dogs by applying selection pressure towards tighter hips. Among current hip screening methods, PennHIP has the highest heritability value to bring about these genetic changes.
For service and working dogs
Service and working dog organizations were the first to adopt PennHIP as the principal method for hip screening. The investment in training service/working dogs is enormous. The ability to prescreen the dog’s genetic predisposition to CHD is an invaluable tool when evaluating a future service/working dog’s hip integrity.
For more information, please check University of Pennsylvania Hip Improvement Program, www.pennhip.org