When Whiskey, a small Munsterlander dog, showed up at the vet's office in November 2011, he was unable to chew. A cancerous growth known as squamous cell carcinoma had grown onto his jawbone, keeping the 9-year-old pooch from enjoying his favorite chew sticks.
Jump ahead to 2013. Whiskey just celebrated his 11th birthday in January and by all accounts is back to his old self, thanks to the success of an experimental procedure performed at the University of California-Davis' Veterinary Medical Teaching Hospital. The creators of this procedure hope that what they've learned could hold lessons for regrowing bones in humans.
"He is really doing so well," said Tom Swierk of San Francisco. He and partner Robin Addams are co-owners of the happy dog. "He plays with the same balls, he chews the same hard chew sticks. There's nothing different in what he does."
Whiskey was the fifth of twelve dogs to undergo the reconstructive procedure, which removes the affected part of the jawbone and replaces it with a sponge-like scaffolding material that eventually grows into the original bone.
Jawbone loss can occur as a result of bone fractures, tumors, severe periodontal disease and infection.
"There weren't great options before this. ... Our main goal was to get the dogs back to their normal state again," said Dan Huey, a biomedical engineer.
Before the development of the procedure, dogs could face removal of the tooth crown, extractions of lower canine teeth, or orthodontic devices that can cause pain and ulcerations in the mouth, Huey said.
Swierk and Addams were devastated upon hearing of their dog's condition from their veterinarian.
"We told our doctor, 'We want the best. Whereverit is,'" Swierk said.
Their veterinarian told them about the experimental procedure.
"We felt that that the ability of going forward with that surgery was absolutely in the best interest for Whiskey. ... We had no reservations," Swierk said.
Huey and veterinary surgeon Boaz Arzi developed the procedure as they looked for possible solutions for bone replacement. They collaborated with Frank Verstraete, professor of veterinary dentistry and oral surgery.
They performed the procedure after an initial evaluation to ensure the feasibility of the operation on the particular dog. Whiskey's was the largest bone removal they performed, with an affected area of almost 2.5 inches.
First, a titanium plate is screwed into place to capture the natural contour of the jaw. Next, the plate is unscrewed and the affected portion of the bone is surgically removed. Finally, the plate is screwed back onto the remaining bone before the scaffolding material is inserted into the gap where the native bone was removed. After two weeks, solid tissue begins to form. Over a period of time, the scaffolding material, which contains a bone growth protein, grows bone cells and replicates the natural bone.
Twenty-four hours after the surgery, Whiskey was able to eat soft canned dog food. Three months later, the bone had completely formed. Three months beyond that, the bone was symmetrical and had achieved its original density.
"The quality of his life, within one month, was exactly the way it had been before," Swierk said. "He was our dog again. He was totally himself."
"It's an amazingly powerful system and is working out really well," Huey said.
Arzi said that of the 12 dogs treated with the procedure at UC-Davis to date, five had conditions that required removing part of the jaw; seven had fractures that never healed or bone sections that were missing.
"It's a journey," Arzi said. "We tell them it's major surgery, but the dogs usually go back to normal function the day after."
With future surgeries lined up, UC-Davis hopes to make this procedure an integral part of its offerings, and researchers hope the procedure could be used in human bone regeneration, though no human trials are underway.
"I imagine that it has a great potential in humans, and I think we will see it in the future," Arzi said. "Think about all the car trauma, gunshot wounds and war injuries in which a big chunk of bone is missing. This basically eliminates the need to take bone from other parts of the body and implant it."
"It's probably going to be in textbooks for years to come as to how this surgery will help humans someday with cancers of the bone or an abnormality of the bone," Swierk said.
Anthony Atala, director of the Wake Forest Institute for Regenerative Medicine, says the procedure may be meaningful to the study of bone regeneration. "It's a great application. It is actually advancing what the growth factor can do in two ways. First you're helping to mold where the bone gets regenerated, and also you're doing it upon larger areas," Atala said.