Brookfield Zoo tiger, slowed by arthritis, gets ‘bionic hip’ replacement in a North American first
The scene at Brookfield Zoo was a tribute to medical science, to cooperation on behalf of endangered animals and, especially, to anesthesiology.
The patient laid out on an operating table amid a roomful of humans was Malena, an Amur tiger, 230 pounds of pure carnivore. Still and silent as her leg was lifted to have her left hip shaved in preparation for the surgeon’s incision, she did indeed look like a big cat.
But still there was, you know, a tiger in the room.
After laughing politely at a joke about being sure to tip the doctor who put the big cat under for the mutli-hour procedure Wednesday, the surgeon, Dr. James Cook from the University of Missouri School of Medicine, said the whole experience was “humbling.”
“You just appreciate how amazing they are and how they are so endangered and why in the world would anyone want to hurt something that beautiful, that majestic,” he said. “And then you just feel privileged, honestly. And not only for that animal. You are helping the species.”
Cook’s task was to install what he called “a bionic hip,” a sort of ball and socket custom made out of carbon and titanium by a Florida medical device firm and designed to boost the quality of life for the very arthritic 10-1/4 u00bd-year-old animal.
“The left hip is — whoo! — bad,” he said. “It’s going to be awesome to restore that.”
The procedure, believed to be the first of its kind at least in North America, was “totally custom,” Cook said. “It involves all the buzzwords today: Some 3D printing. Some virtual modeling. We even did practice virtual surgery from Columbia, Missouri, to Naples, Florida, with images from Chicago, Illinois.”
When Malena arrived at Brookfield last June, transferred from a zoo in Sioux Falls at the behest of North American zoos’ Species Survival Plan for tigers, Brookfield officials knew she had a bad left hip.
The extent of the joint’s arthritic deterioration only became clear, however, when the zoo was able to put her under its CT scanner.
“We were really just surprised at how bad the arthritis in that hip had become,” said Dr. Mike Adkesson, the zoo’s vice president of clinical medicine.
Like all wild animals for whom weakness is an invitation to attack, Malena did a fairly good job hiding her injury, he said. A steady supply of painkillers helped, too.
“We don’t see a whole lot of obvious lameness,” Adkesson said, but instead “stiffness in that back leg … similar to someone in their 60s or 70s who has some hip pain.”
Instead of keeping the Amur tiger — formerly known as the Siberian tiger, and down to about 500 animals in the wild — doped up and simply managing her further decline, “we knew we could make a long-term solution by going down this pathway with the total hip replacement,” the zoo veterinary chief said. “She’s kind of middle-aged, is how I would describe her. She could go on for another six years or so.”
Into the picture came Dr. Cook, Mizzou’s Allen Distinguished Chair for Orthopedic Surgery, who had performed a two-knee cartilage transplant on a Brookfield snow leopard two years ago. In, too, came Arthrex, the Naples company that bills itself as “a global leader in orthopedic surgical device design.”
Arthrex had also worked on the leopard knee surgery and again agreed to donate its services for Malena, Cook said. “They’ll get some good PR, but honestly they’re not going to make money on this,” said the surgeon.
Cook and his team came up to Brookfield in November to perform shoulder arthroscopy on one of the offspring of the snow leopard he had previously worked on and that same day, in a swamp monkey with arthritis from knee and hip trauma, he “cleaned up both those joints.”
The original plan, Brookfield’s Adkesson said, was for Cook to also perform the tiger surgery on the November date, but COVID-19 protocols meant the zoo wanted to limit people’s time in the operating room.
So the doctor, who started as a vet but now works primarily on people, came back on Wednesday, driving up with three members of his surgical team, including his wife, Cristi Cook, a veterinary radiologist.
“It’s an opportunity to basically take a leg and put it back to 100-percent normal,” said Adkesson, “what this cat would have had when she was a year old.”
Fabricating the custom-fit hip replacement parts, centered on the roughly golf-ball sized ball joint, was a challenge.
Essentially scaling up to tiger size the pieces used in dog hip replacements, and then customizing them based on CT scans of Malena’s specific anatomy, the Arthrex design, the company explains, incorporates cutting-edge technology used in human patients, including “a three-dimensional open-celled titanium scaffold designed to assist bone and tissue regrowth following surgery.”
The procedure itself, though, using only a six- to seven-inch incision, was expected to be fairly standard.
“That’s a beautiful thing, to be honest with you,” Cook said. “I’ve done total hips on cheetahs and snow leopards before. The parts all the same so it’s good. Other than the size and her pathology, it’s really pretty consistent across species.”
Still, though, it ended up taking about twice as long as originally expected, six hours rather than three, Adkesson reported.
“It was a little bit of challenge getting it into place, but Dr. Cook was able to work through that and get it in there.,” he said, noting an initial issue with “getting that implant to slip down under the musculature the way we wanted ... It took a little more finagling in terms of getting things to line up appropriately.”
Said Cook, “She had a real lot of scar tissue around the joint and then a lot of remodeling of the bone. It really made it difficult to get access to get the implants in. It was a lot of thinking on the fly and making sure we were doing the right thing, maintaining stability while getting just enough access to get the implants in there.”
The good news, Adkesson said by phone as the incision was being closed back up, is “we’re really happy with the way it looks right now. The joint’s moving real smoothly. It has excellent ranger of motion. Looks nice and secure. All the things we’re looking for.”
And now comes the really challenging part: Limiting the mobility of a supremely agile animal whose left rear leg suddenly feels better than it has in years.
“We can’t say, ‘Bed rest for six weeks,’” Cook explained. “We can’t say, ‘Use your walker for the first two weeks.’”
“The things we’re most concerned about,” Adkesson added, “are the jumping.”
Tigers can jump six to eight feet high and 10 to twelve feet in distance, he said, and “it’s that propulsive force we want to avoid before the muscles have rebuilt and tightened up around that joint.”
Limiting the animal’s motion will be done partly with an anti-anxiety medication, sort of like a Valium type of drug. “We’re just looking to keep her nice and calm and nice and mellow and in a small area so she’s not able to engage in high activity behavior,” he said.
But a lot of the recovery will also be up to the zoo’s animal keepers.
“To me,” Cook said, “you kind of think of the keeper as the athletic trainer for a pro athlete. I have to be perfect for 2-1/4 u00bd hours (in surgery — or for six), but then, really, the real work begins. If this works, full marks to them.”
If all goes well, expect to see Malena up and about — possibly even jumping and on a reduced or even eliminated dose of pain killers — in about six weeks. That is roughly when, coincidentally, the zoo is scheduled to reopen after an extraordinary two-month winter closure prompted by the pandemic.
“We’re always happy when we can make an animal more comfortable (and) we can provide a good quality of life for her for many years ahead,” said Adkesson. “It’s always exciting for us when we’re able to do something that’s innovative and able to push the boundaries for what’s been done before for different animals in a zoo setting.”
Twitter @StevenKJohnson
