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Are all knee implants the same?

Email|Print|Single Page| Text size + By Judy Foreman
July 14, 2008

Not any longer.

Until recently, the implants that orthopedic surgeons put in aching knees have come in a limited number of shapes and sizes, regardless of the gender or knee architecture of the individual patient.

But in the last year and a half or so, two companies - Zimmer and ConforMIS - have been marketing tailored implants designed to fit patients much better than old ones did. These implants are so new that there's little long-term data on them, though four doctors contacted by the Globe - three of whom have close ties to ConforMIS - believe patients recover faster and with less pain with the new system.

To better fit women's knees, Zimmer now sells the "gender solutions" knee that is not just smaller than implants used for men but shaped to fit the contours of women's knees more exactly.

Even more sophisticated is ConforMIS's new individualized implants. It uses an MRI or CT scan to image the patient's knee, then uses a software system to create an exact replica of that patient's knee, said Dr. Philipp Lang, chief executive of ConforMIS and director of Musculoskeletal Radiology at Brigham and Women's Hospital.

The personalized implant "literally pops into place," said Dr. Bruce Bollinger, medical director of the Baylor Surgical Hospital in Fort Worth.

With traditional surgery, said Bollinger, who consults for ConforMIS, doctors have to "irreversibly remove cartilage and bone" to make the patient's anatomy fit the implant. But not with the new system, said Bollinger, who has used the implant in 50 patients so far. "It's not a panacea," he said, but it "has a good chance of getting rid of 80 percent" of a patient's pain.

Dr. Nata Parnes, an orthopedic surgery fellow at Massachusetts General Hospital who has no financial ties to the companies, said the new implants "look very promising, but we need at least five to 10 years of follow up to sure."
JUDY FOREMAN

E-mail health questions to foreman@globe.com.

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