One knee doesn't fit all

Some companies offer replacement options specifically for women

Some companies offer replacement options specifically for women

April 30, 2007|by TIFFANY ARNOLD

Soreness still crept in during physical therapy - her second session since the knee surgery - but Rita Shindledecker was convinced her new knee was special.

Shindledecker, 69, of Waynesboro, Pa., replaced her right knee two weeks ago. She replaced her left knee 11 years ago.

This time, Shindledecker received a knee implant specifically designed for women's bodies - not an option when she got her first knee.

Medical experts say just-for-her knee implants offer the promise of better mobility for women who need a new knee.

Since last year, at least two companies - Zimmer Inc. and Stryker Corporation - have been marketing knees for women, whom they say would have otherwise received implants better suited for men.

"It seems to me like I can tell the difference," said Shindledecker, gripping her healing knee between exercises at physical therapy. "It's healing differently than the other one did. It doesn't take so long for the pain to go away."


Until recently, women and men received the same knees, even though women's knees have a different shape than men's.

Universal knees could accommodate size differences but often did not account for the differing shapes of men's and women's knees, a cause of discomfort for some women, said Dr. Tom Amalfitano, an orthopedic surgeon in Hagerstown who performs 50 to 60 knee procedures a year.

About 9,584 women nationwide have received Zimmer's knee between Jan. 1 and March 31 this year, said Chris Smith, an orthopedic consultant for Zimmer.

Shindledecker is among the nine women in the Tri-State region to get the Zimmer knee, Smith said.

Women comprise more than half of all the total knee replacement surgeries in the U.S. annually, according to National Center for Health Statistics data. In 2004, the most recent year for which figures are available from NCHS, women accounted for 311,000 of the 478,000 total knee replacement surgeries.

Demand for new knees is projected to grow even more - to 3.5 million replacements by the year 2030, according to a recent study by Exponent Inc., a scientific and engineering consultant firm.

Amalfitano said total knee replacement surgery is required when the cartilage at the ends of the thigh and lower-leg bones wears away, causing pain and other damage. Surgeons resurface the damaged area with metal and plastic. But it can take months before the implant recipient can see the difference - less pain and better mobility.

"The implants are never intended to replace God's parts," Amalfitano said.

There also is some concern that there isn't enough scientific research to back up the claim that gender-specific knees provide better outcomes for women.

"I would encourage more research to go forward," said Dr. Jeffrey Katz, a rheumatologist and spokesman for the National Institute of Arthritis and Musculoskeletal and Skin Disease (NIAMS).

Spokespeople for NIAMS and the American Academy of Orthopaedic Surgeons said they could not point to a study that supported the claim that female knee implants worked better.

"It's a compelling idea that a better-shaped prosthetic can create better outcomes, but it's not something we'll know overnight," Katz said. "You'd need an entire generation in order to find an answer."

Katz is an associate professor of medicine and orthopedic surgery at Harvard and at Brigham and Women's Hospital in Boston.

The knee made by Zimmer did undergo mechanical testing, according to documents submitted by Zimmer to the Food and Drug Administration.

Shindledecker said she didn't have any problems with the universal knee implant she received 11 years ago. But she hopes to have even better mobility after the new, gender-specific implant on her other leg heals.

Before she got the surgery earlier this month, Shindledecker said the simple act of picking up her great-grandchildren was a struggle.

"Sometimes (my right knee) would hurt so bad that I was afraid if I picked him up it would lock up on me and I would fall," Shindledecker said. "Then it got to the point where it hurt to walk."

At physical therapy on Thursday morning, Shindledecker was able to bend her knee 108 degrees, something unthinkable a month ago today.

"It's amazing what (doctors) can do for you now," Shindledecker said.

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