It's not a magical, mechanized process, according to Beck. The surgeon must still input data correctly. And it is the surgeon who must pin the little cutting jigs or guides on the bone in the right place. The system helps ensure that. Also, with standard knee surgery, "if you make an incorrect measurement on the first cut, it's a mess the whole way." Navigation is more likely to prevent mistakes and, if one is made, correct for it, he says.

It adds about 15 minutes to knee-replacement surgery and there's a learning curve. Just entering data takes Beck about five minutes, now that he's done a number of them. More than a dozen patients have had the surgery at Jordan Valley since the hospital installed the system.

The concept's not new. Similar systems, many of them by Stryker, have been used for other parts of the body.

Most patients are in the hospital two or three days and older ones often spend a week or two in a rehab hospital after knee replacement. But within a month, most patients are back at work, unless their job involves manual labor. Therapy typically takes a couple of months and knee function is likely to improve gradually for a whole year. Still, within three or four months, most patients can walk and golf and do normal activities.

Elaine Schwanebeck, 52, had her knee replaced using the system in December. She'd lost all the cartilage in the knee and was miserable.

She works as an academic program coordinator for the University of Utah Moran Eye Center ophthalmology department. She was walking within two hours after surgery with a walker. She was diligent in working on rehab, using the continuous positive motion machine for eight hours a day. After several more weeks of outpatient therapy, she does the exercise at home and now has 120-degree range of motion. And she was back at work not long after surgery.

If she could do her other osteoarthritis-stricken leg tomorrow, she would, she says. "I was willing to try anything. This has been great."

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E-mail: lois@desnews.com