OK, there are probably more than 100 different surgical procedures. But two in particular are specialties of the da Vinci surgical robot: prostatectomies and hysterectomies.

And women seem to love Intuitive Surgical's (Nasdaq: ISRG) surgical systems more than men. Or rather, their doctors do. Hysterectomies passed prostatectomies as the No. 1 procedure performed on a da Vinci system last quarter.

The number of prostatectomies remained flat quarter over quarter, and Intuitive Surgical doesn't expect it'll grow much in the U.S. going forward. While the first surgical procedure developed for the system may be maxed out, there's still plenty of growth remaining. Procedures grew 36% year over year in the second quarter, and the company thinks it can keep that pace for the rest of the year.

Intuitive Surgical has a typical razor and blade model similar to Hewlett-Packard's (NYSE: HPQ) printers and ink cartridges. Sell a robot (printer) and then sell the accessories (ink) used on it over and over again.

But unlike the typical razor and blade model, the increase in the number of procedures performed can also work in the other direction on the model, increasing system sales. After all, there's only so much time available on the machines at a hospital. As one procedure becomes popular, the hospital needs to purchase an additional machine to satisfy the higher number of surgeons who want to (or can) use it.

Going forward, hysterectomies will continue to grow because it's a large market, but there's potential for growth into ear, nose, and throat procedures; lung surgeries; and surgeries to remove fibroids from uteruses. There's also global expansion into places like Japan, where the da Vinci was just recently approved.

Can Intuitive Surgical keep up the 50% revenue growth rate it's seen so far this year and justify its monster P/E that towers over medical-device makers St. Jude Medical (NYSE: STJ) and Medtronic (NYSE: MDT)? (Intuitive's P/E is three times that of the other two.) In the short and medium term, I don't think it'll be a problem unless hospital capital spending tightens again under some sort of double-dip recession.

In the long run, Intuitive Surgical will have to be innovative, looking for the next big thing to drive growth. Considering how the company has timed its move from prostatectomies to hysterectomies, investors should have confidence that management can keep the growth train on track.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool owns shares of Medtronic. The Fool has a disclosure policy.