AAOS fellows treat 600-lb polar bear for femur fracture

It’s not often that orthopaedic surgeons make house calls to set femur fractures. But when the patient would cause a panic if she appeared in a clinic or emergency department setting, surgeons from the Campbell Clinic in Memphis, Tenn., were willing to make an exception.

The patient, a five-year-old female polar bear at the Memphis Zoo named Cranbeary, broke the femur in her left hind leg on Feb. 7, 2007. No zoo staff members witnessed Cranbeary’s accident, but an onlooker reported that a three-year-old male named Payton scuffled with Cranbeary on a cliff overlooking a dry moat in their outdoor exhibit, causing her to fall 14 feet and break her leg.

Cranbeary was in heat when the accident occurred. Although male polar bears often behave aggressively when females are in heat, this was unusal behavior for Payton.

Orthopaedic advice needed

Terry Dew, DVM, who was part of the bear’s surgical team, contacted AAOS fellow Edward Perez, MD, for advice on setting the bone. Because plates and screws for repairing femurs are designed for humans rather than bears, Dr. Dew consulted with Dr. Perez about using these devices to repair the large animal’s femur, which was broken in two places. Dr. Perez then volunteered to assist and brought along two colleagues—Paul A. Whatley, MD, and Mark A. Pierce, MD—who also assisted with the procedure. Zoo veterinarians Mike Douglass, DVM, and Dawn Zimmerman, DVM, rounded out the surgical team.

There were no complications during the three-hour surgery, which was performed on Saturday, Feb. 10. The surgical team used two stainless steel plates and 26 screws donated by Smith & Nephew, Inc. to align and immobilize the femur. The medical device maker also provided about 200 tools and a surgical support team.

Obesity, noncompliance issues

Although Cranbeary is the right size for a polar bear, her girth made it difficult to take detailed X-rays before the surgery, and fluoroscopy was impossible on the large animal. The bear’s anatomy, however, was much like a human’s, according to Dr. Whatley.

“The preoperative X-rays that we had were fairly limited, so we weren’t 100 percent sure what we were going to find. Other than that, it was surprisingly similar to operating on a person,” said Dr. Whatley. “The femur that we could see could have very easily been mistaken for a human femur. The musculature was a little bit larger, but it was all in the same places as a human’s, and the approach that we used was the same.”

Cranbeary’s recovery will be more challenging than it would be for the average human not only because of the amount of weight the plates must support but also because polar bears, unlike people, don’t use crutches after leg surgery. That’s why the surgeons implanted two plates instead of just one, which would be adequate for a human.

“We added a second plate because you can’t tell a polar bear not to put weight on its leg,” said Dr. Whatley. “After you perform this kind of surgery on a human, you can require the patient to be non-weightbearing for some time. The polar bear stood up right after she woke up from anesthesia and started to put some weight on it. We hoped that by using two plates, the implant would be strong enough and hold up long enough for the broken bone to heal.”

A successful outcome

“It was the best surgery that we could possibly have hoped for,” said Memphis Zoo President and CEO Chuck Brady in a press release issued after the surgery. “The bone in her leg is healing, and she is resting well.”

According to Emily Schultz, team lead keeper at the Memphis Zoo, Cranbeary’s attitude and appetite have been good. The bear is now standing up and walking around more frequently, but spends most of her time on her bed of straw. Cranbeary will recover in the zoo’s onsite hospital until she is ready to go back to her exhibit sometime in April.

“The staff is very pleased with her progress and we hope to keep seeing improvements every day,” said Schultz recently in the “Cranbeary Keeper’s Log” on www.memphiszoo.org

The zoo is considering modifying the moat in the polar bear exhibit and is seeking advice from other zoos with similar exhibits. It may also implement a stricter policy about keeping male polar bears separate from females when males show signs of aggression.