SCIENCE / MEDICINE : ‘Robodoc’: A Steady Hand for Surgery : Innovation: Engineers, surgeon and veterinarian develop robot to aid in operations. It won’t replace doctors, but will help ‘equalize care,’ creator says.
In an unusual collaboration, a team of robotics engineers, a surgeon and a veterinarian have developed a robot that promises to alter the practice of orthopedic surgery drastically and may become an important tool for many other types of operations.
Over the last two months, the hips of six dogs afflicted with severe arthritis were replaced successfully using a robot surgeon, nicknamed “Robodoc.” Howard (Hap) Paul, a veterinarian who holds the unusual position of assistant professor of orthopedics at the UC Davis Medical Center, and Sacramento surgeon William Bargar anticipate using the new device on human patients in about a year.
Robodoc doesn’t replace surgeons, said Paul, 41, who has been the driving force behind the project since its inception four years ago. But it is a tool that helps them be more accurate.
“The robot will equalize care so that surgery in small towns is as good as surgery in the big cities,” he said. “It has the potential to be used anywhere where you need precision. Things like brain tumor biopsies and neurosurgery on the spine can be made more accurate and safer.”
The robot surgeon’s first use on humans, said Paul, will be in hip replacements, which require drilling a long, narrow hole into the thigh bone to provide an exact fit for a titanium hip implant. Surgeons now create the hole for the implant by hammering a large spike in the shape of the implant into the femur. It is an inexact method, because they cannot see the type of bone tissue that will come in contact the implant, and the bone often cracks from the strain of hammering.
Because the method is so inaccurate, said Paul, on average only 21% of an implant is in contact with bone after surgery and many gaps remain where no contact is made at all. About 30% of the gaps between the implant and the bone are 1 to 4 millimeters wide, which makes it difficult for bone to grow on the porous metal implant and anchor it.
That explains why 25,000 of the 160,000 hip replacements done annually are repeats, Paul said. Because Robodoc achieves 97% contact, with gaps measuring .05 millimeters, Paul believes robot-assisted hip replacements will last 20 to 30 years.
Paul, his assistants and the robotic engineers tested Robodoc on foam, plastic bones and cadavers. Their tests were so successful that they were confident they could perform the surgery on dogs needing a hip replacement.
“We never had to put an animal to sleep (in experimenting) with this,” Paul said.
In the operation to replace the arthritic hip of Susie, a 4-year-old German shepherd, Paul began normally. In the clean, bright but small operating room of the medical group where Paul practices, he opened up the anesthetized dog’s leg, removed the femur from the hip socket, sawed off the round head, and implanted a new titanium socket to replace the arthritic one.
“Look at that,” he said as he pointed out the damaged bone. “It’s a mess. This dog was in a lot of pain.”
To prepare for the operation, three locating pins had been surgically placed into Susie’s femur two days before, and she was put through a CAT scan to provide cross-sectional views of the bones. The digital tape from the CAT scan was loaded into a computer, which incorporated the information into a program call Ortho-dock. The program provides a three-dimensional view of the bone that can be moved around on the screen.
Before the surgery, Paul used Ortho-dock to select the correct size of the implant. Engineers were able to incorporate the sophisticated imaging techniques of the Lansat satellite, which takes pictures of Earth from orbit. The technique makes it possible to apply different colors to different types of bone, allowing Paul to discern the shape and size of the inside of the femur where the titanium implant was to be placed. From the program’s inventory of implants, he selected one and checked its fit on the three-dimensional model on the color monitor.
The current method most surgeons use to select an implant is much less accurate: Just before the hip-replacement operation, surgeons place different size implants on top of X-rays to approximate the fit.
After he had inserted a new socket, Paul and assistants Brent Mittelstadt, a UC Davis biomedical engineering doctoral student, and Peter Kazanzides, an IBM robotics engineer, moved Robodoc into place and securely clamped Susie’s leg to the machine. To orient Robodoc, Mittelstadt used its pressure-sensing probe to touch the three locater pins in Susie’s femur--two at the knee and one at the top of the bone--so that it would locate itself in relation to the bone and associate that internal “image” with the three-dimensional picture of Susie’s leg on the computer screen.
Refitted with a drill bit one-third of an inch in diameter, Robodoc was checked one last time by Kazanzides, and Paul gave the approval to drill. Robodoc was turned on and the operating room sounded like a dentist’s office.
“You say, ‘Cut,’ you go have a cup of coffee, and the robot does all the work,” Paul quipped.
It wasn’t quite that easy. While Robodoc carefully drilled a long hole in the femur, Paul, Mittelstadt and two assistant surgeons sprayed water on the drill to keep it cool and suctioned out the waste. They monitored the robot’s progress on the computer screen, where a white probe slowly progressed down the inside of the femur to show how much had been drilled away.
Fifteen minutes later, Robodoc was done. Paul inserted the implant and tapped it gently into place. He snapped a titanium connector into the implant in the femur, popped the ball at the other end into the socket, and began stitching up Susie’s leg.
Paul and Bargar envisioned a machine like Robodoc 4 1/2 years ago after working with Techmedica, a Camarillo company that was pioneering the use of CAT scans to design custom implants for hip and knee replacements.
“We were frustrated because we could make a high-tech prosthesis using digital data to run a . . . cutting machine,” Paul said. “But we were still using funky tools to make the hole. If we could control the outside, why couldn’t we control the inside?”
They took their idea to Bela Musits, a research scientist and manager of systems management and control at IBM’s research division in Yorktown, N.Y. Although most of the robots designed by IBM are for light assembly tasks in the computer industry, the robot language developed by the company was complex enough to direct a robot in a task such as drilling a hole to conform accurately to a three-dimensional image.
IBM decided to fund the research, and its engineers began working with Paul. Later, Mittelstadt spent a year in Yorktown learning how to work with the robot. Paul also worked with computer programmers in IBM’s Palo Alto research center for a year to develop Ortho-dock, the computer program that communicates with the robot.
Early this year, IBM turned over the robot and the computer programs to Paul’s lab at UC Davis, where he, Mittelstadt, Bargar, Kazanzides and two other programmers performed mock operations on plastic bones and cadavers.
Paul has high hopes for Robodoc. “Eventually, when you get real-time imaging in surgery, a surgeon will be able to direct a robot to follow a CAT scan or MRI (magnetic resonance imaging) or ultrasound,” he said. It will be able to do small breast biopsies by following the information from a mammogram and locate and remove brain tumors, Paul said.
In the meantime, he and his team will do about one hip replacement a week on dogs for the rest of the summer to prepare for the first one in humans, which Bargar will perform.
And Susie? She’s home and doing fine.
REPAIRING A HIP
‘Robodoc’ was developed as a surgeon’s tool to improve the accuracy of certain surgical procedures. It’s first use on humans will be for hip replacements. Here’s how the procedures works:
1. Three calibrating pins are placed on the femur, and a CAT scan provides cross-sectional views of the bone. Cat scan information is incorporated into Ortho-dock program, which provides a three-dimensional view of the bone on a computer screen.
2. Doctors open up the leg, remove the femur from the hip socket, saw off its round head, and implant a new titanium socket to replace the arthritic one.
Leg is clamped securely to Robodoc. It’s pressure-sensing probe is used to touch the three calibration pins so that it can locate itself in relation to the bone and the three-dimensional image on the computer screen.
3. Robodoc drill a long hole in the femur, while doctors monitor progress on the computer screen.
4. Doctors insert implant and tap it into place. Titanium connector is snapped on to the implant, ball is popped into the socket, and leg is stitched up.
