Glad to the Bone

March 31, 2011

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Zeus, a five-year-old Siberian husky, is self-conscious about his left foreleg.

“Whenever he meets another dog, he tucks it in and hides it,” says Sandy Vandall, his owner. “It’s like he doesn’t want the other dogs to see that he doesn’t have a foot.”

Zeus lost his foot as a puppy, when another dog attacked him and bit it off. The injury limits him to the use of three legs, severely curtailing the active dog’s mobility.

“He wants to run and play, but he tires out after about five minutes,” Vandall says. “It really affects his quality of life.”

Fortunately, Zeus will have a special surgery to replace his missing foot. Dr. Denis Marcellin-Little, professor of orthopedic surgery, and a team of NC State engineers and surgeons are providing Zeus with a custom-made, osseointegrated implant that will replace the faulty wrist joint and front paw.

Marcellin-Little and Dr. Ola Harrysson, associate professor of industrial and systems engineering, are pioneers in osseointegration, a process that fuses a prosthetic limb with an animal’s (or human’s) bones. They began their work on osseointegrated pet prosthetics in 2005 with a cat named George Bailey, who was born without the lower half of his hind legs.

Since then, the collaborators have improved and strengthened the design and streamlined the manufacturing process. They are working to improve healing of the skin and tissue around the implant.

Zeus’ limb surgery will be the third performed on a dog at NC State.

Custom-Made Foot

NC State is the only university in the world that can manufacture custom prosthetics for veterinary patients in house, thanks to the close collaboration between veterinarians and engineers.

For Zeus’ implant, the engineers began by creating a 3-D computer model of the limb based on CT scans. The hard part is getting the replacement limb to fit just right.

“We look at it, the surgeons look at it, and everyone decides on the best design,” Harrysson says. “We fabricate that design, then we do rehearsals to perfect it. It can take three or four tries before we’re happy.” Fabricating the implant takes five to eight hours.

Although the implant is strong enough that Zeus could be up and running as soon as a week after surgery, but Marcellin-Little says that’s probably not a good idea. “That bone hasn’t ever borne weight, so we have to give him weeks to walk before he can run. We will be monitoring what his bone is doing, how the skin is healing, and we will make those decisions about how active he can be further down the road.”

Sandy Vandall is prepared for the long recovery ahead. And Zeus? “Oh, he’s ready,” she says. “You can tell he just wants to have a full and active life.”