Creating One Language
Dr. Dottie Brown, director of Penn Vet’s Veterinary Clinical Investigations Center (VCIC), and Dr. Gail Smith, inventor/director of PennHIP, have a shared goal: to develop and implement validated outcome tools to be adopted across the field of veterinary medicine in order to serve orthopedic patients more effectively.
“Most orthopedic surgeons would agree that our ultimate goal is to restore quality of life for our patients and clients,” said Dr. Brown. “To accomplish this goal, surgeons must make decisions regarding application of diagnostic and therapeutic modalities. An outcomes-based medicine approach to decision making gives surgeons confidence that they are helping owners make the best decisions for their pets.”
Dr. Smith agrees. “We have to use the most validated tests – it impacts animal welfare,” he said. “As veterinarians, we are responsible to advance animal welfare issues and comfort. And to do that successfully, you need to validate the tests you depend on to make treatment decisions.”
Both Dr. Brown and Dr. Smith are working to create evaluation methods that can be adopted by all practicing vets in order to further the mission of the profession and provide a common language when evaluating orthopedic patients.
Arthritis Assessment at the VCIC
In 2006, a group of Diplomates from the American College of Veterinary Surgeons, which included Dr. Brown, initiated the Canine Orthopedic Outcomes Measures Program (OPM) with the aim to develop and validate standardized tools to determine and compare outcomes of various interventions in clinical cases, studies and research work. These tools will allow the veterinary community to better understand, provide and communicate to others the true outcomes of the surgeries, medications and physical modalities used.
Dr. Brown, whose previous questionnaire, the Canine Brief Pain Inventory (CBPI; www.canineBPI.com), which allows owners to assess the severity of chronic pain in their dog and how that pain interferes with the animal’s normal functioning and is now recommended by the FDA, became the scientific lead on developing a new assessment that could be globally adopted to include an owner assessment and gauge success of clinical trial treatments in arthritic dogs.
“The most common orthopedic disease we see in patients is arthritis,” said Dr. Brown. “That’s why we chose to develop questionnaires measuring pain and function in dogs with the disease. We wanted to ask owners, ‘How do you know your dog is being affected by its arthritis and how do you know when it is feeling better?’”
Dr. Brown’s first step, in conjunction with her colleagues, was to develop an owner assessment first with the goal to develop a veterinary assessment tool next.
To create the owner assessment, focus groups were held, during which owners of arthritic dogs were asked a series of questions about their dogs’ behavior and evidence that their dogs were in pain.
Next, Dr. Brown and her team studied the transcripts from the focus groups.
“We looked for key words,” said Dr. Brown. “Were there common behaviors owners were noticing? Are there common themes through the conversations? We included owners of dogs that had surgery, as well as some that had not; we wanted a broad range to ensure the forms we develop are valid in a broad range of patients.”
After summarizing observations, general questions were drafted and vetted among a different cohort of owners whose dogs had arthritis.
“We wanted to look at how people answered the questions and look at which answers are most reliable,” said Dr. Brown. “It was an iterative process until we finally said, ‘I think this is it.’”
The current form of the assessment is being tested through the VCIC’s Arthritis Assessment Study, which is underway.
For veterinary orthopedists, standardized client questionnaires and clinical assessment forms for function and quality of life that are validated are a logical approach for addressing the current shortcomings in study design and implementation.
In many cases, outcome assessments used in veterinary medicine have not been adequately evaluated for reliability and validity as opposed to assessments used in human orthopedics, in which the development and validation of outcomes instruments is well documented.
“This is an ethical undertaking as well as a scientific one,” said Dr. Brown. “And it is more and more important that veterinary orthopedists speak the same language and agree on the same methods for evaluating our techniques as the profession grows more quickly and aggressively. We owe it to our clients and to our patients to be able to validate our methods, procedures and recommendations for care and pain management.”
Promoting the PennHIP Method
“The integrity of screening tests is paramount to the success of selective breeding to lower the incidence of hip dysplasia in dogs,” said Dr. Smith whose PennHIP method aims to accurately diagnose susceptibility in puppies so that breeders know which dogs should and should not be bred.
Canine hip dysplasia, or CHD, is defined by the radiographic presence of hip joint laxity or osteoarthritis with hip subluxation (laxity) early in life. A developmental disease of complex inheritance it is the most common orthopedic disease in large- and giant-breed dogs and causes pain and loss of mobility.
Currently, there are two screening methods used by breeders in the US: the Orthopedic Foundation of Animals (OFA) method, which relies on hip-extended radiographs, and the PennHIP method.
The traditional OFA screening method relies on conventional hip-extended (HE) radiographs, which Dr. Smith argues do not provide critical information needed to accurately assess passive hip joint laxity and therefore osteoarthritis susceptibility.
“We believe the insensitivity of the OFA method for detecting hip joint laxity is not the fault of the expert radiologist interpreting the HE radiograph, but rather an inherent deficiency of the HE radiographic view,” said Dr. Smith.
In order to achieve genetic control of CHD and create a system that would have more accurate diagnostic outcomes, Dr. Smith developed the PennHIP method as a more effective way to evaluate whether a dog will develop canine hip dysplasia (CHD) in its lifetime. His method has gone head-to-head with the traditional OFA hip-screening method, which was developed in the early 1960s.
Most recently, Dr. Smith offered a comparison of the PennHIP method against the OFA method in the September 2010 issue of JAVMA, where he illustrated that the PennHIP method called for more stringent breeding practices in order to lessen the prevalence of CHD.
PennHIP vs. OFA
The PennHIP method quantifies hip laxity using the distraction index, or DI, metric, which ranges from a low of 0.08 to greater than 1.5.
Smaller numbers mean healthier hips.
The PennHIP DI has been shown in several studies at multiple institutions to be closely associated with the risk of osteoarthritis and canine hip dysplasia. It can be measured as early as 16 weeks of age without harm to the puppy.
The OFA grades hip joints in dogs in seven categories: excellent, good, fair, borderline, mild, moderate and severe hip dysplasia. The scoring system is a pass/fail one.
The PennHIP method is not pass/fail, but rather it quantifies on a continuous scale the “risk” of a dog acquiring OA. It considers a DI of less than 0.3 to be the threshold below which there is a near-zero risk to develop hip osteoarthritis later in life. In contrast, dogs having hip laxity with DI higher than 0.3 show increasing risk of developing hip osteoarthritis earlier and more severely, as the DI increases.
Comparing the overall results of the study, 52 percent of dogs OFA-rated “excellent,” 82 percent of dogs OFA-rated “good” and 94 percent of dogs OFA-rated “fair” fell above the PennHIP threshold of 0.3, making them all susceptible to the osteoarthritis of CHD though scored as “normal” by the OFA. Of the dogs the OFA scored as “dysplastic” all had hip laxity above the PennHIP threshold of 0.3, meaning there was agreement between the two methods on dogs showing CHD or the susceptibility to CHD.
The key feature of the PennHIP radiographic method is its ability to determine which dogs may be susceptible to osteoarthritis later in life. Because dogs are recognized as excellent models for hip osteoarthritis in humans, Dr. Smith’s PennHIP technology may be a viable option for human medicine.
“In humans, with appropriate studies of course, it is conceivable that mothers of susceptible children may adjust a child’s lifestyle, including diet, exercise and physical therapy to delay the onset or lessen the severity of this genetic condition,” Dr. Smith said.
Outcomes and Next Steps
In the meantime, Dr. Smith’s findings point to a weakness in current dog-breeding practices. If breeders continue to select breeding candidates based upon traditional scores provided by the OFA, then according to Dr. Smith, susceptible dogs will continue to be paired and hip quality in future generations will not improve.
Despite well-intentioned hip-screening programs to reduce the frequency of the disease, canine hip dysplasia continues to have a high prevalence worldwide with no studies showing a clinically meaningful reduction in disease frequency using mass selection.
“We’re sending mixed messages,” said Dr. Smith. “If we care about dogs then this is something that shouldn’t be ignored.”
Knowing a dog’s risk for osteoarthritis early allows veterinarians to prescribe proven preventive strategies like weight loss to lower the risk of the genetic disorder. Also, dog breeders now have a better way to determine breeding quality to lower the risk of hip osteoarthritis in the future generations of dogs.
Dr. Smith urges veterinarians to take a proactive role in educating clients about this new school of thought in preventive medicine.
“Have a conversation about a pet with its owner when the pet is a puppy,” said Dr. Smith. “Educate the owner that the PennHIP procedure, performed, say, at the time of spay or castration, will permit assessing the probability of the dog’s developing the OA of hip dysplasia at some point in life. Then follow up by recommending know preventive measures, such as calorie restriction, to help the dog live a long, healthy, pain-free life.”
This new approach is known as “predictive medicine.”
PennHIP is currently in common use by service-dog organizations such as the US Air Force, the US Army and numerous dog-guide schools. There are approximately 2,000 trained and certified members currently performing PennHIP procedure worldwide. For more information on becoming PennHIP-certified, visit www.pennhip.org.