Jack is a Labrador mix who spent the first three years of his life trying to balance on his front legs and drag his hindquarters around behind him.
That's because he lost his back paws as a puppy. He was a rescue so no one is quite sure what happened to him, but his whole life changed last spring.
Jack's family heard of a program at North Carolina State University that fits animals with 3D printed prosthetic limbs. They flew him out from Tucson to Raleigh and tried the experimental procedure.
After six hours of surgery, Veterinarian Orthopedic Surgeon Dr. Denis Marcellin-Little had attached two titanium feet to the bone on Jack's hind legs.
Today Jack is a happy dog who walks and runs, just like any other pooch.
"His personality has changed, which was a bit unexpected," Marcellin-Little said. "He is much more relaxed and friendly now. He used to be much more subdued and nervous. This has really changed the way he perceives himself and the world."
By using a 3D printer, NCSU Assoc. Prof. Dr. Ola Harrysson was able to attach tiny beads to the metal that helped Jack's bone attach itself to the prosthetic. It's something he doesn't think he would be able to do without a 3D printer.
Marcellin-Little also noted that using a 3D printer allowed him to perfectly match the contours of Jack's bone to the socket of the prosthetics.
It's an experimental procedure that, by Marcellin-Little's own account, "isn't quite ready for primetime yet."
The doctors at NCSU have performed the surgery on 10 animals since 2005 with varying degrees of success, but they are getting closer to perfecting it.
"Some people think it's silly what we're doing, but our goal is to do this with people someday," Harrysson said. "You have a lot of guys coming back from the war needing prosthetics, and we can help them."
The new type of prosthetic, with a metal end attached to the bone, allows amputees to easily snap attachments on and off. That same process can take as much as a half hour with a conventional prosthetic, which makes it a very cumbersome task for someone who might need to do it just to go to the bathroom, Harrysson said.
Harrysson figures his team is still a few years away from trying this procedure on a person, though doctors have already tried a simpler form of the procedure in Sweden.
"(Recipients) are rock climbing and parachuting, in other words, leading normal lives," Harrysson said.
Jack might not be parachuting anytime soon, but there just may be a squirrel or two who are in for the chase of their lives in his future.