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Today in Your Health, baby boomers are getting more knees replaced. This year about 300,000 women will undergo the surgery. Subtle differences in female anatomy have led to the development of gender-specific implants.
NPR's Allison Aubrey reports.
ALLISON AUBREY: Kathleen Sheekey is 64 years old and has always been active. She plays tennis, loves to travel. But last year during a trip to New York she realized her knee pain was really slowing her down.
Ms. KATHLEEN SHEEKEY: I would be walking through the Metropolitan Museum of Art and calculating how far along in this exhibit can I make it before I have to find a bench. And that's not me, and I didn't like that.
AUBREY: Sheekey says increasingly she found herself hailing cabs instead of walking. And as the pain got worse, she relied on ibuprofen, glucosamine supplements, and a knee brace for as long as she could.
Ms. SHEEKEY: I think I knew I was at the end of the line, and I think it was, you know, three decades of playing tennis mostly on hard courts had just worn it down.
AUBREY: The first orthopedic surgeon she went to see told her just hang on, wait a few more years before having a knee replacement.
Ms. SHEEKEY: To which I thought, well, why? Why wait? It's not going to get better and I'd like to get on with my life and live it as fully as possible.
AUBREY: So last March, Sheekey scheduled a knee replacement operation with surgeon Anthony Unger. He heads the Minimal Invasive Surgery Center at George Washington University. And for the last year he's been using a new kind of gender-specific knee implant in many of his patients.
Dr. ANTHONY UNGER (Minimally Invasive Surgery Center, George Washington University): So I have the implants available in the operating room, and I find out what best fits for that particular patient.
AUBREY: Unger says he explained to Sheekey, as he does all his patients, that the new gender knee hasn't changed the basic way he performs the surgery. What he does is to cap the two bones that meet at the knee - the thigh and the shinbone - with metal and plastic surfaces, or implants. The gender knees are simply a subtle redesign of older implants.
Dr. UNGER: Well, female anatomy is a little different. The end of the bone, called the femur, is a little different contour. The angles that the implant makes with the bone is a little different, and that leads to a little different design.
AUBREY: Unger says he likes the new implants because after doing about 200 surgeries, he finds there are fewer cases of the implant hanging over the bone. It's not exactly a custom fit, but the idea is that it's a little better tailored.
Kathleen Sheekey says she is very satisfied with the results, and five months out she's now back to playing tennis - albeit a little more cautiously.
Ms. SHEEKEY: I do hold back. I don't try to make Hail Mary shots anymore. But you know, when you're in your early 60s, maybe you don't make them anyway. So I'm fine with it. I play it for the joy of it.
AUBREY: More importantly, she is walking around comfortably, pain-free.
Experts say that Kathleen's strong recovery likely has much more to do with the effort she put into physical therapy after the surgery and the fact that she was still fairly strong and fit before the operation than it has do with the specific implant the surgeon used.
Ms. DIANE COVINGTON (Physical Therapist): It's true that people who are in better shape coming in are in better shape going out.
AUBREY: Diane Covington is a physical therapist who now works as a physician's assistant to the knee replacement practice at Duke University. She says lots of patients are now calling in asking for the gender knees, partly because one manufacturer, a company called Zimmer, is heavily marketing the knee implant directly to people via the Internet.
Covington says she takes time to explain to patients that it's just one option. There are more than a dozen manufacturers all making different-sized implants.
Ms. COVINGTON: I tell them that they need to have a knee that fits their knee best based on their anatomy, that the gender knee may not be the best choice for them, and that they need to keep an open mind about that.
AUBREY: Covington says the most important decision a consumer does make is choosing a surgeon.
Ms. COVINGTON: You want to choose a surgeon who is fellowship-trained in total joint replacement surgery.
AUBREY: This means they've completed a post-doctoral fellowship focused exclusively on replacing joints, and they're likely performing at least 150 surgeries per year.
Ms. COVINGTON: And you want to ask them what their track record is and what their complication rate is.
AUBREY: Outcome studies show that about 90 percent of knee-replacement surgeries, regardless of which implant is used, are successful. This means that one year out patients report significantly reduced pain compared to before their surgery and are able to walk up and down stairs with almost the same amount of mobility they had before they hurt their knee.
Among the surgeries that fail, infection is the top culprit, followed by a failure or loosening of the implant. The majority of replacements hold up for 15 years; after that a repeat surgery is likely needed if someone's healthy enough. And it's still unclear how well these second replacements hold up.
For now, Kathleen Sheekey says she's feeling great about her morning strolls.
Ms. SHEEKEY: So far so good. But we're approaching the corner and we're going to turn right and walk up hill.
AUBREY: Whether the gender knees will play any role in improving the outcomes is unclear. Surgeon Anthony Unger says the competing implants will likely never be compared head to head.
Allison Aubrey, NPR News.
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