Knee replacements just for women

// 12 July 2007

Firms in the US are marketing knee implants specifically designed for women, reports Orthopedic Technology Review.

Currently, women are fitted with implants designed for men – but this causes some pain and discomfort:

Hitt explains his involvement with Stryker. “In 2001, a couple of other surgeons and I had some interest in creating a knee implant designed for women patients. The products on the market were all too wide for women, resulting in a lot of overhang. Experienced surgeons could compensate by making adjustments, but why should they have to?”

So, it’s great that an implant is being designed for women, right? Well, according to this article, women make up 60% of all cases of knee-replacement surgery. You’d think they’d have actually come up with an implant that fits before this, rather than shoving in ones designed to fit the minority of patients.

Here is Robert Booth, MD, chief of Orthopaedic Surgery, Pennsylvania Hospital in Philadelphia’s perspective on why more women than men need implants, and why they need them specifically designed for them:

“Because women’s hips are wider, the angle of the femur is greater than that of a man. We call it the Q-angle,” he says. “So if you make a part that accommodates that angle, then the knee cap will track more naturally on the front of the femur. Women’s knees have three differences: They are taller and not as wide; they’re more delicate—not as thick in the front; and the angle at which the knee works—the Q-angle—is greater in women.”

But Kirby Hitt, MD, assistant professor at Texas A & M University Health Sciences Center College of Medicine, has another theory – the patriarchy is taking our knees:

The average age of his female patients is 64, and he has his own theories as to why women are more in need of knee implants than men, beyond the longevity issue. “I think child-bearing may be a contributing factor, creating more stress on the knees than we caregivers realize. I also think women, as the primary caregivers in their families, don’t have a lot of time in their schedule, so they put off a problem that might be solved or delayed by conditioning and exercise until it’s too late, and surgery is then needed,” he says.

But is it really “women’s” implants that were needed, or just smaller ones? This doctor uses them on both female and male patients:

Adolph Yates, MD, assistant professor of orthopedic surgery at the University of Pittsburgh, takes a more measured view of the new female knee implants. Not on the payroll of Stryker, Zimmer, or any of the other orthopedic companies, Yates thinks the new products should be viewed as “gender-friendly” rather than gender-specific, per se. On average, he performs about 100 knee implant surgeries a year, the majority for women, and he does like the Stryker Triathlon’s “wide range of sizes, which, as the company claims, do tend to fit women better.”

On the other hand, Yates says, “I’m equally happy with the results of men whom I’ve used the product for.” And for both genders, he particularly likes the product’s ergonomically favorable design that increases flexion (bending of a joint) and the attention given to the relative constant center of rotation.

(Thanks to Emma for the link)

Photo by Chevysmom, shared under a Creative Commons license

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