PennHIP at the University of Melbourne Veterinary Hospital
Marjorie Milne, Registrar in Diagnostic Imaging, has achieved certification as a PennHIP Member allowing the UMVCH to offer the PennHIP method for evaluation of dogs for Canine Hip Dysplasia (CHD).
CHD is a commonly inherited problem in many breeds of dogs, particularly large and giant breeds. It arises from loose fitting hip joints and can result in pain, difficulty moving, reluctance to play and jump, and severe osteoarthritis. In an attempt to reduce the incidence of this crippling condition, many dog breeders use hip x-rays to screen their breeding dogs for evidence of hip dysplasia, preferring to breed from dogs with ‘low scoring’ or ‘tight’ hips.
There are two methods for assessing dogs for CHD in Australia. The long established “hip extended” method has been administered by the Australian Veterinary Association (AVA) and the Australian National Kennel Council (ANKC). The AVA/ANKC scheme requires accurately positioned hip x-rays that can be taken by any veterinarian. Dogs assessed by this method must be 12 months of age or over, and require a general anaesthetic for accurate positioning. The x-rays are submitted for evaluation and scoring by a trained Veterinary Radiologist. The hips are assessed for several characteristics, including the closeness of fit of the joint, the presence of arthritis, and the ‘Norberg Angle’ to objectively measure the fit of the hip joints. A hip score is provided and this can be compared to the breed average. Breeders are encouraged to breed with dogs that have a hip score better than the breed average.
The PennHIP method was developed by the University of Pennsylvania Hip Improvement Program. The main difference from the AVA/ANKC method is that instead of relying on the appearance of the hips in the extended view, the hip joints are actively distracted using a special positioning device to reveal the maximum hip laxity. Dogs must be under sedation or general anaesthesia to allow accurate positioning, and special training and certification is required to ensure the best quality, consistent x-rays are obtained. PennHIP members must attend an information seminar and undergo rigorous training before achieving certification. The hip x-rays are sent to Pennsylvania for evaluation. A Distraction Index (DI) is objectively measured and compared to the breed average to assist breeders in choosing dogs for breeding. The DI provides an indication of the likelihood of developing hip arthritis later in the dog’s life, with a DI of < 0.3 ("tight" hips) associated with a low risk of developing arthritis. The PennHIP method has been shown to reveal ‘loose’ fitting hips in some dogs that may appear to have ‘good’ hips with the hip-extended method. Additionally, dogs may receive a preliminary PennHIP evaluation as young as 16 weeks of age, with follow-up evaluation at 6 months to one year of age. This ability to evaluate dogs at a younger age can assist breeders in making management decisions for their breeding stock, and enable pet owners to assess their pet’s risk of developing hip arthritis.
Currently both AVA/ANKC and PennHIP methods are recognised by the AVA. Each method has its advantages and disadvantages, and it is up to the breeder or pet owner to choose which scheme they would like to participate in. The important thing to remember is to take the results of the scoring system into account when making breeding decisions, with an aim to always breed with animals with scores better than the breed average. Once this is done, improvements in the overall breed average can be achieved, with a reduction in the incidence of the crippling arthritis that can occur with Canine Hip Dysplasia.
For more information on either the PennHIP method or on the AVA/ANKC methods of evaluating dogs for Canine Hip Dysplasia, or to make a booking, please contact the Diagnostic Imaging Section on (03) 9731 2326, or email vet-radiology@unimelb.edu.au
Diagram: Ventrodorsal view of the pelvis with the hips extended.
Diagram: Ventrodorsal view of the pelvis with the distraction or PennHIP method. Note the increased joint space width revealed with the distraction method.
