RALEIGH, N.C. – Because Cyrano weighs more than 20 pounds, amputating his cancer-weakened leg was out of the question. So the tubby tabby’s owners turned to doctors and engineers at North Carolina State University to get him back into mice-catching trim.

Last week, the 10-year-old cat from Upperville, Va., received what doctors believe is the first feline total knee replacement in the U.S.

“This is the most complex implant that NC State has made and really, in all honesty, that anyone has built for any situation that I know of,” said surgeon Denis Marcellin-Little, a French-born veterinarian.

Cyrano – his full name is Mr. Cyrano L. Catte II – underwent treatment last year at Colorado State University for cancer in his left hind leg. The disease is in remission, but the treatment left the leg nearly useless and extremely painful.

Marcellin-Little and NC-State engineer Ola Harrysson are pioneers in osseointegration, a process that fuses a prosthetic limb with living bone. In 2005, Marcellin-Little performed the world’s first surgery to fuse leg implants with a cat’s bone tissue, so Cyrano’s owners turned to him for help.

Britain’s Dr. Noel Fitzpatrick was credited with the world’s first total knee replacement in 2009 on a cat named Missy, whose leg was crushed by a car. But Marcellin-Little said Cyrano’s plastic and cobalt chromium alloy implant is more like those used in humans.

“It has a form of articulation that is unique – that allows the implant to bend and rotate,” he said, demonstrating with a model during a news conference the day before the surgery. “The devil is in the details.”

Such implants have become commonplace in dogs. But a cat’s smaller anatomy has proved more difficult to work with, and Cyrano’s damaged bones posed an additional challenge, Marcellin-Little said.

Unlike other joints, which are machined, Cyrano’s knee – in cats, it’s actually called a “stifle” – was fabricated using a laser process that hardens metal powder to exactly replicate his bones. More than a dozen people worked on developing and testing the implant, each half of which is about 2 inches long.

Marcellin-Little practiced the procedure four times on plastic models before Thursday’s surgery.

The operation began around 10:30 a.m. Attendants did not wheel Cyrano to the intensive care unit until almost 5 p.m.

Marcellin-Little said the tabby’s girth and big bones were a plus. He said Cyrano should be up and around in about a week.

“We would like him to take it easy for about three months after surgery,” the doctor said. “And then we will let him be himself.”

Because so much of the time and material were donated, university representatives could not give a total cost estimate.

“Part of this is a pure research project, in a way,” said Harrysson, an NCSU professor of industrial and systems engineering.

The bill to owners Sandra Lerner and Len Bosack will be around $20,000.

“He’s my child. And if it were your child, would you begrudge the money?” Sandra Lerner said.