Are gender-specific knee implants necessary?

If you're a woman and among the half a million people going in for knee replacement surgery every year, you've probably heard about the implant designed with the female anatomy in mind.

"I can tell you that inter-operatively, there are cases where the shape of the femur, particularly the distal femur, can be different, or can be a size that doesn't seem to fit with the standard implants we have," says Craig DellaValle, M.D., associate professor of orthopedic surgery at Rush University.

The Gender Solution Knee by Zimmer addresses that concern. It's been on the market for about a year. An animation provided by the company shows its implant is narrower and thinner than the traditional ones.

But is this design change necessary?

"Our research shows that men and women are getting equal and comparable results from the unisex knee replacements," says Dr. Timothy Brox.

Brox is a Kaiser orthopedic surgeon who analyzed results of nearly 20,000 patients compiled in the Kaiser Permanente National Joint Registry. Two years after surgery, he found women had equivalent or better pain relief than men, and about the same amount of complications.

"We found that the men and women were equally satisfied with their surgery and that their range of motion was also very similar," says Dr. Brox.

Almost all the patients in the Kaiser study had standard knee replacements. What remains unanswered is whether results for female patients could be even better using gender-specific implants.

"It gives you as a surgeon lots of different choices. The questions in my mind are, 'will those translate into better clinical results.' And I think the answer is right now, we don't know the answer to that," says Dr. DellaValle.

Orthopedic surgeon Dr. Chris DellaValle uses the gender-specific implants selectively because they are more expensive and not proven yet to offer better results.

"Sometimes I'll look at the x-rays and I'll pick up on something and I'll say, 'I bet this patient has a more gender-shaped morphology,' and inter-operatively we have trial components and we can see how they fit, and how the knee feels, but again, we're making subjective decisions," says Dr. DellaValle.

Dr. Brox says many women come to him who have read about the gender implants online.

"What I tell them is I too have done my homework and I feel confident that it's not necessary," says Dr. Brox.

To learn what the American Academy of Orthopedic Surgeons think about this topic, click here.

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