Knee implant designed for a woman's body

Surgeons at LDS Hospital Tuesday night became the second group in the world to implant a "gender-specific" artificial knee.

The new knee implant is specifically designed for female patients. The surgery was performed on Rosemarie Brinkerhoff, 78, of Lovell, Wyo.

LDS Hospital orthopedic surgeon Kim Bertin, who performed the surgery, said the anatomy of a woman's knee is very different from that of a man. The female knee tends to be longer from top to bottom and narrower from side to side, while the male knee tends to be shorter and wider. Before the new Gender Solutions' knee was developed, one type of knee implant, geared more towards the male knee, was widely used, and that made implant surgeries more complicated and less successful for women.

"It turns out we we're putting men's shoes on women's feet (by putting) men's knees in women's knees," said Aaron Hofmann, a professor of orthopedic surgery at the University of Utah, who worked with Bertin on the surgery.

Another major difference the implant will account for is the angle that a woman's knee moves. The new implant will be at an angle that is more natural to a woman's body so it will move more easily with the patient.

Bertin said that because older types of knee implants were geared towards the shape of men's knees they often were too wide for women's knees and overhung the bone, causing pain, limited motion and even instability in some patients.

Hofmann said problems with the old implants often had to be fixed in surgery. Now, he said, the new implant will make the surgery process much easier.

"We were chasing our tail in surgery trying to address these problems (created by the old implants)," he said.

While Hofmann said the old implant was adequate for most patients, he and other surgeons wanted the implant to be as close as possible to a real knee.

"Patients were happy with the old implant but we wanted more — we wanted a normal knee," he said. "We're searching for the maximum motion. The new implant probably added five to 10 degrees more motion in patients."

The majority of knee replacement patients, about 60 percent, are female, Bertin said, so it's important that implants be tailored to their knees. But while the "gender-specific" knee is mainly tailored to females Bertin said it's important to keep in mind that knee sizes vary. In addition to the new "gender specific" implant, Zimmer Inc., the manufacturer of the implant, is now making more implant sizes to match individual knee sizes.

"Some men's (knees) are more like women's and some women's (knees) are more like men's," Bertin said.

Brinkerhoff said she is grateful for people like Bertin and the innovations they have made to help improve her life. She said life was difficult after her knee condition worsened.

"I had to use a crutch to get up and down stairs," she said. "My knee was swollen and enormous."

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E-mail: dgardiner@desnews.com