UF Veterinary Team Implants Artificial Knee In First-Ever Procedure

November 19, 1996

GAINESVILLE—An aging Western cougar with a bad knee now has a new one after University of Florida veterinarians surgically implanted a prosthetic device for the first time in an exotic cat.

“This type of procedure is common in humans but not in animals, and to our knowledge has never before been done on a nondomestic cat,” said Dr. Avery Bennett, assistant professor of wildlife and zoological medicine at UF and a veterinary surgeon.

The cougar, a 17-year-old female named Tabatha, had chronic arthritis — technically known as degenerative joint disease — in her right rear knee. The operation took more than four hours and was performed in collaboration with Dr. Steven Gilson, a veterinary surgeon from Phoenix. The cougar, also known as a mountain lion or puma and related to the Florida panther, is recuperating well.

“This was definitely a team effort, ” Bennett said. “If we’re successful, we may break new ground to help endangered animals in the future, as well as enhance this cougar’s quality of life.”

Big cats generally live longer in captivity due to regular veterinary care and better nutrition, and therefore are prone to developing age-related joint disease. Up to now, exotic cats with these conditions at best faced amputation of the affected leg. Far more often, they were euthanized.

UF veterinarians and representatives from the Central Florida Zoological Park in Seminole County, Tabatha’s home, hope the procedure will provide a new tool for keeping endangered cats alive longer for breeding purposes.

“Anything that would allow rare or endangered animals to function reproductively for a longer period of time could be beneficial in terms of protecting the species from extinction,” said the zoo’s general curator Fred Antonio.

Gilson, who has successfully performed total knee replacement surgery in dogs, flew to Gainesville at Bennett’s request when the cat’s owners gave the thumbs-up to proceed.

During the procedure, surgeons removed the ends of the two bones — the tibia and the femur — that make up the knee joint and installed temporary implants to ensure a proper fit. Next, they removed the trial implants and put in permanent ones, secured using bone cement.

The device, made of a substance known as ultrahigh molecular weight plastic, resembles an elongated “D” and is used to provide an artificial surface between the tibia and the femur, said Bert Savell, a representative with the Zimmer Wright Co., which manufactures the implant and donated it for Tabatha’s surgery.

“Basically, we replace both bone surfaces with an artificial surface so that bone will no longer rub against bone, alleviating arthritic pain for the cat,” Gilson said.

Antonio said the zoo, which contracts with UF for veterinary services, had been monitoring Tabatha’s condition for several years.

“Unfortunately, the problem joint had been actively deteriorating,” Antonio said. “In September of last year, X-ray films taken at UF helped us to determine that Tabatha not only had fluid in her knee, but also additional bone growth.”

An annual physical examination performed earlier this year confirmed that the cougar’s condition was worsening. Tabatha could walk but was obviously in pain and putting very little pressure on her right rear leg, Antonio said, adding that the situation became a quality-of-life issue.

“I truly feel we were able to make this cat more comfortable,” Gilson said. “We did not have a lot of other options.”