February 2004

Hip Checker for Easier Surgery

New hip-replacement technology allows smaller incisions, reducing pain and speeding recovery.

By Corie Lok

If you're one of the 300,000 Americans going in for traditional hip replacement surgery this year, you can look forward to an incision 15 to 25 centimeters long, two to three months of waiting before you can take long walks again, and a 1 to 4 percent risk of dislocation. But new technology could make the surgery a lot less onerous. An emerging class of computer navigational systems will allow surgeons to conduct hip replacements through incisions as small as four centimeters and to align implants more accurately. That could mean less pain, faster recovery, and reduced risk of joint failure.

Spherical reflectors on hip surgery tools help doctors see an implant's location.

Minimally invasive surgery itself is nothing new. But it generally involves a pinpoint of light at the end of an endoscope that guides a surgeon's tools during a very localized procedure, like gall bladder removal or a heart bypass. With major orthopedic procedures, surgeons need a far wider view. To provide that view during hip surgery, several companies, including Smith and Nephew Orthopedics of Memphis, TN, and Biomet of Warsaw, IN, in partnership with z-kat of Hollywood, FL, are bringing guidance systems to market.

A Smith and Nephew system is typical. It starts with half-centimeter spherical reflectors affixed to the patient's bones and to the surgical instruments. A conventional CT scan then provides a map of the pelvic area. During surgery, an infrared-light-emitting camera bounces light off the reflectors and registers their position. Software produces an image that shows the surgeon where his or her tools are and displays precise measurements.

Smith and Nephew received approval from the U.S. Food and Drug Administration last year for this hip surgery system; 25 surgeons worldwide are testing it on humans. Z-kat and Biomet, among other companies, are in advanced stages of the approval process. Not only do better imaging systems reduce trauma, but the precise measurements they provide will help less experienced surgeons do a better job and "make results more consistent across patients," says Anthony DiGioia, a surgeon and director of the Institute for Computer Assisted Orthopaedic Surgery at the Western Pennsylvania Hospital in Pittsburgh.

Hip surgeries are the latest guided orthopedic procedures; versions for spine and knee surgeries already exist. While these systems still must become more user friendly, "there's no doubt that they will be mainstream," DiGioia says.