Consider the three-legged dog. Maybe you have one, or you saw them in the park or in one of the billions of Dodo videos about them. Skewed but resilient, they evoke in us humans a kind of fawning sympathy unmatched by the typical four-legged friend.
“People are attracted to pets with disabilities,” said Rene Agredano, a co-founder of the pet amputation support website Tripawds. “I think it is attractive that we just want to help them. We just want to make sure they have an equal chance of a happy life. “
That desire to help is increasingly manifesting itself as prosthetics, especially in cases where the animal has lost more than one limb. Pets with artificial limbs have become a genre of feel-good videos all their own. A cat with bionic hind legs. A turtle with wheels. The clips make the rounds on Facebook, where they add a touch of feel-good optimism to the otherwise heavy deluge that is your news feed. 3D printing has propelled the industry forward. Printed prosthetics can be lightweight, affordable and infinitely customizable. Doctors make beaks for birds. High school students build artificial dog paws in their spare time.
But not all pet prostheses are created equal. And some vets and people in the tripod community are concerned that the proliferation of easy-to-work attachments could lead to unintended consequences for the critters they carry.
Walking distance
Dogs can lose a limb for a variety of reasons. Maybe they were born with an abnormal limb, or they were hit by a car, or they developed a cancerous growth that required an amputation. A common quip among tripod enthusiasts is that “dogs have three legs and a spare.” It is true, to an extent. Dogs adapt remarkably well to losing a limb, says Theresa Wendland, who specializes in animal sports medicine and rehabilitation at the Colorado Veterinary Specialist Group. But complications can arise if the animal makes up for what is missing. In older dogs and dogs with arthritis or other mobility problems, extra weight on the remaining limbs can be a major problem.
“It really affects the mobility of their spine,” says Wendland. “They need to change the range of motion in their other limbs. They have to pull themselves forward in a way that is very unnatural. “
Dentures, if made properly, can restore that range of motion. But no matter how the heart melts to see a three-legged dog running on four legs again, building a good paw for a puppy isn’t easy. Wendland, who works with the orthopedic and prosthetic company OrthoPets to help dogs adjust to their new limbs, says it’s a complicated process that takes time and technical know-how.
As with human prostheses, an animal prosthesis must be individually adapted to the build of the wearer. This means that we have to take into account the size, weight, height, posture and gait of the animal. (A doberman kit does not fit a Dachshund.) To do that, orthopedists must study the animal’s movements and try to form a limb that is in sync with the others. While techniques vary, the standard process is to make a cast, design the prosthesis from photos and video, and then build it out with durable thermoplastics and metal. From there, they adjust the finer details by hand until it works with the animal. The process can take weeks.
There is also an issue of the amount of limb to replace. The ideal place to place a prosthesis, says Wendland, is as low on the limb as possible. But when the whole limb is gone and there is no clear point to attach a prosthesis, it becomes much more difficult.
One leg up
3D printing has long been hailed as a manufacturing revolution in many industries, including prosthetics. And now a New Jersey-based design firm called Dive Design thinks this is the solution for full limb replacement. It has partnered with a company called Bionic Pets that is building exactly what the name implies: accessibility technology for pets. Derrick Campana, who runs Bionic Pets, has long been hand building prosthetics for pets. (He even called a show about it The Wizard of Paws, which airs on the Brigham Young University television channel.) About a year ago, he invited Alex Tholl and Adam Hecht, heads of Dive Design, to his Virginia lab to see how he could improve the process.
“One thing that kept coming up was the need to develop a full limb prosthesis,” says Tholl. The limbs Campana built used too many resources and required too much labor to be manageable. Plus, Tholl says, “With the waste that went with it, it just didn’t make sense financially. For us the wheels started to turn. “