June 29, 2017

Pets and Prosthetics: Growing Interest, Advancing Technology

The use of prosthetics in humans dates to ancient times. Significant advancements have been made over the millennia, and pets are now beginning to reap the benefits.

By Don Vaughan
Teddy was just 10 weeks old when he was surrendered to Boston Terrier Rescue of North Carolina, an organization that fosters Boston terriers in need of a forever home. The playful puppy was a unique case because he was missing his front paws and back toes, which made mobility difficult, says foster caretaker Barbara Bradley of Wake Forest, who adopted Teddy to ensure he received the special care he needed.
 
After consulting with her veterinarian about having Teddy fitted for prosthetics on his front limbs, Bradley was referred to the North Carolina State University College of Veterinary Medicine in Raleigh, where doctors and rehabilitation specialists have been advancing the field of prosthetics for years. Teddy was a good candidate, she was told, but he would have to reach maturity before the work could be done.
 
“It was always my intention to get Teddy prosthetics,” Bradley says. “He was basically walking around on his wrists and I knew that wasn’t comfortable for him. I wanted him to have the best quality of life he could have.”
 
When Teddy reached his first birthday, he was fitted with silicone sleeves that attach to lightweight carbon-laminated “feet.” “The first time we put them on, he acted really funny, like, what’s on my feet?” Bradley recalls. “But very quickly he got the hang of them.”
 
Teddy is one of a growing number of pets to receive prosthetics to correct a disability, most commonly the partial loss of a limb. “I would definitely say there is an upswing in both interest as well as providing that clinical service,” observes Jamie Peyton, DVM, DACVECC, CCRT, CVA, CVC, chief of the Small Animal Integrative Medicine Service at the University of California, Davis Veterinary Medical Teaching Hospital. “Owners want their pets to have a good quality of life, and mobility is certainly an important part of that for animals.”

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Yesterday and Tomorrow
The use of prosthetics to correct disabilities in humans dates back to antiquity, reports the nonprofit Amputee Coalition. In 1858, an artificial limb dating to about 300 BC was found in Capua, Italy. Made of bronze and iron with a wooden core, the prosthesis apparently was made for a below-the-knee amputation. The Roman historian Pliny the Elder wrote about a Roman general in the Second Punic War who had an iron fist made after he lost his right arm so he could hold his shield and return to battle.
 
The evolution of human prosthetics has seen steady technological innovation in both the materials from which prosthetics are made and their design, resulting in greater comfort and functionality. Dramatic refinements occurred following the Civil War, World War I, and World War II, all of which witnessed a dramatic increase in the number of veterans returning home with missing limbs. Today, many prosthetic devices are controlled via advanced microprocessors.
 
As with other aspects of medicine, many advances in human prosthetics have trickled down to the veterinary side. “On the material side and on the design and fabrication side, we often use materials adopted by prosthetists for people,” notes Denis J. Marcellin-Little, DEDV, DACVS, professor of orthopedic surgery at North Carolina State University College of Veterinary Medicine. “We might incorporate a hinge for a pediatric knee into a dog device, or the tamarack hinges used in a human ankle might be incorporated into a dog ankle or elbow.”
 
Transdermal osseointegration is one area in which veterinary medicine has taken the lead, reports Dr. Marcellin-Little, who consults on approximately 200 prosthetic cases around the country each year. The procedure involves implanting a titanium rod directly into the bone at the end of the impacted limb and attaching a prosthetic foot to the protruding post. Only a handful of animals have undergone the procedure to date, but it shows great promise, he says.
 
Another area for growth is the use of 3D scanning, which can create a more detailed image of the residual leg, making for a better prosthetic fit. “In addition, the use of 3D printers will allow us to make a more precise model of what we’re trying to create,” Dr. Peyton notes. “It may also make prosthetics less expensive in the future.”
 
Why Prosthetics?
Animals require prosthetics for a variety of reasons, one of the most common being neonatal injuries resulting in amputation. “It’s sometimes unclear why very young puppies lose portions of their limbs,” Dr. Marcellin-Little says. “It could be an overactive mother who cleans the umbilical cord and mistakenly chews the end of a newborn’s foot.”
 
Trauma is another common reason for amputation, as are tumors of the extremities, especially the toes. “Tumors of the nail bed must be excised, along with a portion of the foot,” Dr. Marcellin-Little explains. “Roughly an inch of tissue must be removed around the edge of the tumor to prevent regrowth.”
 
But just because an animal might benefit from a prosthetic device doesn’t always mean it will receive one. A tremendous number of factors come into play in determining whether an animal is a good candidate, including the age and size of the animal (very small and very large dogs pose greater challenges), the amount and health of the residual limb, soft tissue coverage, and skin mobility relative to underlying tissue. Other issues include possible orthopedic problems in the limb, how the limb is innervated, whether the partial limb is affecting the range of motion in adjacent joints, and gait issues.
 
A Tough but Successful Case
Teddy is a good example of a challenging case because he’s small, his limbs are bony, his skin is fragile, and he likes to chew on things. “I decided the best approach would be to apply a suspension concept used in human prosthetics, but we wondered if we could achieve this on such a small scale,” says Heather M. Davidson, CO, BSc, O&P, a pediatric orthotist with Bio-Tech Prosthetics and Orthotics, the Durham, North Carolina– based company that manufactured Teddy’s devices.
 
Custom silicone liners were made to protect Teddy’s residual limbs, and tiny components were incorporated into the distal ends for suspension, Davidson explains. Dacron and Velcro straps attach to the ends of the silicone liners and pass through slots in the sockets, which provide stability for Teddy at his wrists and cover the liners so he can’t chew on them. In addition, soling material was added to the sockets to provide traction and shock absorption and to stop Teddy from wearing out the laminated sockets.
 
“Teddy’s mom approached the finicky challenge of donning and doffing very optimistically and Teddy took to his new feet like a champ,” Davidson says.
 
The patient’s personality also plays a role. Is the pet friendly and easy to work with? How has it adapted to the loss of a limb? How active is the pet? “The patient profile will influence whether a device would be effective,” notes Dr. Marcellin-Little. Even the client affects the decision. Does the client own other animals? Does the owner have the time and is he or she committed to helping the pet learn how to use the prosthetic device? Most importantly, does the client have the patience to follow through, because optimizing fit and retraining can be very time-consuming.


 
The Challenges of Rehab
Indeed, it can be a challenge getting a patient used to moving about on its new mechanical limb(s). “The initial training is getting the patient comfortable wearing it and putting weight on it, then helping build muscle strength to be able to use it properly,” Dr. Peyton says. “People always assume that once you put a device on an animal, it will automatically start running. But if you compare it with a person who receives a prosthetic leg, you know the pet will have to go through rehabilitation as well. It’s a requirement at our facility that a prosthetic patient be in therapy for at least 10 weeks.”
 
According to Barbara Bradley, Teddy is still learning how to get around on his artificial feet. “He tires out when using them. It’s a bit of exertion as he gets used to them,” she says. “He gets halfway around the
pond we walk around and, when he tires, I put him in my dog stroller for the rest of our walk. I’m letting him set the schedule. When we get back from our walks, I’ll leave the prostheses on him for a little while; he’ll go to bed and take a nap with them on. He just treats them like they are normal feet.”
 
The Power of Collaboration
Veterinary prosthetics is, by necessity, a collaborative endeavor. “I think it’s important to work as a team because as veterinarians we don’t always have specialized training in prosthetics, so we must collaborate with human prosthetists,” Dr. Peyton explains. “Veterinarians understand the biomechanics
of animals better, as well as how we want something to work for them. But human prosthetists bring all their knowledge. They go to school to learn how to build devices and make them fit well.” Other members of the team may include orthopedic surgeons, oncologists, rehabilitation specialists, and the family veterinarian, who will observe and care for the patient for the rest of its life.
 
Once a patient receives a prosthetic device, the results can be life-changing. In addition to enabling improved, more comfortable mobility, prosthetics can help prevent a variety of health problems later on. Dr. Peyton believes the value of prosthetics is 2-fold. “One, it helps prevent more chronic changes
that could cause pain for the patient long term as it compensates for the missing limb, such as the development of arthritis and spinal issues. And two, it allows the animal to be more functional. Dogs and other animals want to have independent movement. Providing that support allows them to resume activities they may not have been able to do as much, such as running and playing.”

Looking to The Future
As the science of prosthetics continues to advance, its future looks bright. “Our first goal should be greater knowledge and education about veterinary prosthetics,” states Dr. Peyton. “My hope is that this becomes a standard option for owners, meaning [that] if their pet has to have an amputation that all veterinarians will know the value of prosthetics and give them that choice. The next step would be further development of the devices, whether it be continual advancement of the socket to make them fit better or the potential of osseointegration. I think that will be another big advancement as well.”
 
 
​Don Vaughan is a freelance writer based in Raleigh, North Carolina. His work has appeared in Military Officer, Boys’ Life, Writer’s Digest, MAD, and other publications.

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