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October 14, 1999
image: KCSA Worldwide

Peter Deschenes needed a new hip. Years after a football injury, the dentist suffered from near-constant groin pain. "I had to plan when to go to the mall, where to park, how many stores [I could walk to]," he recalls. "The strategy to minimize pain became very important."

When he decided to become one of more than 250,000 Americans who receive new hip sockets each year, it was not an easy decision to make. Many of these implants are imperfect and will loosen, which necessitates a second, more expensive surgery—and a greater chance of more complications. Even worse, the replacement hip only lasts 10 years, assuring someone his age of needing that second surgery.

Yet in the future the presence of safer and much more precise surgeons could make such decisions easier. The only difference is that the surgeons are machines .

Well What’s Wrong With Regular Hip Surgery?

Diagram of hip replacement
An artificial joint (darkened) connects the hip and the femur.
image: Maquet Corporation

In traditional hip surgery, the bone is gouged out by hand with router and rasping tools and the titanium pins holding the implant to the bone are cemented in place, as the hole made by human hands is never precise enough to simply drive in the pins. Dr. Joseph Fetto, M.D., an orthopedic surgeon at NYU Medical Center, explains why it’s vital to place hip implants correctly: "The biggest difficulty is trying to get the bone to accept the device. If there is not a perfect fit [between the bone and the implant], there will be movement between the two pieces, and that causes pain. Very often the pain may cause the operation to fail and have to be redone." A second surgery is also more expensive: Dr. Fetto estimates that a revision might be as much as $100,000, compared to an initial surgery cost of around $25,000.

A more effective implant involves the use of porous materials placed as close as possible to the bone. The patient’s own bone eventually will grow into the implant, strengthening the bond between artificial joint and natural bone, and lengthening the time the implant will last. The Center for Orthopaedic Research recommends a gap of less than 0.25 mm (0.008 of an inch) between the implant and the femur for a successful fixation. But surgeons were unable to create small enough holes in which to place the porous pins.

Enter the robosurgeon.

OK, How Does It Work?

image: Encore Orthopedics

Robotic surgical systems are bringing the art of surgery into the cyber age. Two of them—ROBODOC Surgical Assistant System, and its competitor CASPAR (Computer Assisted Surgical Planning and Robotics)—work by using computed tomography (CT) scans to quantitatively measure the patient’s femur for precise placement of the titanium pin which holds a hip implant in place. The human surgeon uses this information to determine the proper size and shape of the hip implant before the surgery. This information is stored in the robotic surgeon’s memory.

On the day of surgery, the surgical team prepares the patient by positioning the base of the robosurgeon next to the operating table. This base has a special bone clamp that prevents any movement of the femur during surgery. After the human surgeon removes the damaged femoral head (the "ball" of the hip socket) the robotic assistant takes over.

image: Integrated Surgical Systems, Inc.

The human surgeon directs his or her robotic assistant to mill the femoral canal to make a precisely-sized hole to accept the implant pin. The porous pin, which will directly contact the bone over 90 percent of its surface area (compared with only 30 percent of traditional implants), will allow bone to grow into the implant and fix more quickly and for a much longer period of time.

Will Robosurgeons Replace Humans?

Dr. Fetto emphasizes that robosurgeons will never take the place of humans. "It’s very important to understand that the physician or surgeon can be trained to do a lot of things, and the skill is not necessarily doing it, it’s knowing when to do it. The not a threat, it’s really a’ll do the operation better and with more proficiency [using a robot tool]."

When Will Robots Enter Our Operating Rooms?

Some trials have begun, but the Food and Drug Administration has yet to license anyone to perform hip replacement robosurgery in the U.S. Robosurgeons can be found in European hospitals, where they are used on a regular basis. Someday, robosurgeons could become a routine item in American operating rooms.


Elsewhere on the Web

"Robots In the Operating Room," an article by the FDA.

"Robot-Assisted Hip Surgery," at Northwestern University’s website.

The Center for Orthopaedic Research

The Center for Medical Robots and Computer Assisted Surgery

"The Future is Here. Does It Work?" American Academy of Orthopaedic Surgeons Bulletin, August ’98

Integrated Surgical Systems, creators of ROBODOC

MAQUET Corporation, creators of CASPAR

Sutter General Hospital in Sacramento
New England Baptist Hospital in Boston
Shadyside Hospital in Pittsburgh

by STN2

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