Robotics Surgery: Robots in the Operating Room

by Food and Drug Administration (FDA)

Imagine you're having a hip replacement, a fairly common operation, especially if you're an older American. As you're wheeled into the operating room, you notice the nurses and anesthetist preparing for your surgery.

But wait, someone's missing. Your surgeon.

You look around the room and finally spot the surgeon, off in the corner keying information into a computer terminal. And there, next to the doctor and computer is a 500-pound, 7-foot-high, jointed steel arm, with a tiny drill attached to one end.

It's Robodoc. And it's going to assist in your surgery. During the procedure it will drill the hole in your thigh bone (femur) that will hold the anchor of your new hip joint.

While robots have long been used to assist surgeons during operations, the devices may soon take a more active role in surgical procedures such as hip replacements, removal of brain tumors, prostate surgery, and laparoscopy.

But, while medical robots may make some surgical procedures easier or help the surgeon perform an operation more precisely, the Food and Drug Administration, which regulates these new devices, has several concerns. One concern is software. Today's robotics devices typically have a computer software component that controls the moving, mechanical parts of the device as it acts on something in its environment.

FDA reviewers evaluate the software components of such devices because the software is "command central" for the device's operation.

When evaluating the devices, FDA looks to see if the company is following good software engineering practices in writing and designing the software. These practices often include establishing device requirements, writing good specifications, evaluating the software and device, analyzing the device's potential hazards, and implementing controls that specifically address those hazards. Other concerns include the safety and effectiveness of the hardware component of the device.

Robodoc

Robotics devices being developed today take computer technology to a new level of sophistication. One of the most ambitious projects, and probably the best known in the United States, is Robodoc — a modified industrial robot that performs certain aspects of a surgical procedure. It was created by Howard Paul, D.V.M., a veterinary surgeon, and William Bargar, M.D., an orthopedic surgeon. (Paul died of leukemia Feb. 10, 1993.) The device made history and headlines late last year when it drilled a hole in a femur to hold a patient's hip implant in place without cement.

Ten robot-assisted human hip replacements using Robodoc were performed at Sutter General Hospital, Sacramento, Calif., under an investigational device exemption (IDE) approved by FDA Oct. 9, 1992. The first was done Nov. 7, 1992, on a 64-year-old man suffering from osteoarthritis, the condition most commonly necessitating hip replacement. The surgery took nearly six hours, about double the usual time for more traditional hip replacement procedures.

The last, performed Feb. 11, 1993, took two hours and 40 minutes — about the same amount of time it takes a surgeon to perform the operation using traditional tools. Before approving the IDE, FDA paid particular attention to the software and back-up safety systems.

"When you talk about things that are computer-controlled or automated, people tend to believe that if it's automatic it's better," says FDA biomedical engineer Theodore Stevens. "But, like any computer, [Robodoc] only does what you tell it to do.

"It takes sophisticated software to run a robot or milling machine. As a result, there's some really serious software questions, especially for a device that actually operates on humans."

FDA uses two criteria to classify all medical devices. The first is whether a device is equivalent to an existing device that has been on the market since before May 28, 1976 — the day FDA began implementing the Medical Device Amendments to the Food, Drug, and Cosmetic Act. If it is equivalent, the new device is classified the same as the existing device. If a device does not meet the first criteria, FDA evaluates it according to a second criterion: It is considered a class III device that must undergo clinical testing and have FDA approval before it can be sold. Robodoc falls into this classification.

Because they may pose a significant risk to the patient's health, all new class III devices must be evaluated for safety and effectiveness.

Robodoc, for example, cuts the patient without direct human control of the cutting tool, according to Mark Melkerson, acting chief of the orthopedic devices branch in the Center for Devices and Radiological Health's office of device evaluation.

As a result, there has to be a very well-controlled software development program and there have to be physical limits on how much the device's cutting tool can move. In fact, there are built-in safeguards to make sure the device drills only the femur and doesn't cut into soft tissue, Stevens adds. Robodoc was born out of Paul's and Bargar's desire and attempts to improve the fit of implants in the femur in cementless total hip replacements. About one-third of the 250,000 hip replacements performed in the United States each year are cementless.

Unlike procedures that use cementing materials to fix the implant in place, porous cementless hip implants, introduced in the mid-1970s, are made with porous coatings that allow tissue to grow directly to the implant, holding it firmly in place.

"Our hypothesis was that if we could do the surgery more precisely, then the outcome would be better," Bargar says. FDA's Stevens explains that with traditional replacements, free space between the implant and the bone may allow the implant to move, which could be painful. The implant also might take more time to "fix" rigidly or might not "fix" at all. Theoretically, Robodoc makes possible very close physical contact between the bone and the implant stem, reducing pain and improving the "fix" of the replacement.

In planning for a traditional hip replacement, the surgeon takes a picture of the patient's femur using computed tomography (CT) or magnetic resonance imaging (MRI). The surgeon then overlays these pictures with acetate templates of implants until a close match is found for that particular patient.

During surgery, the doctor removes both the hip socket and the top of the femur. Using a hammer and broach (a cylindrical cutting tool with teeth on the surface), the surgeon chisels an 8- to 10-inch-deep hole down the length of the bone — an imprecise method at best. The surgeon then hammers the steel or titanium implant into place, attaches it to the hip socket, and sews up the incision.

About the Author

www.fda.gov
FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.