Steady Hands for Microsurgery
One hurdle that the field of medical robotics has had to overcome is the surgeon’s natural reluctance to cede control of the actual surgical device. Over time, surgeons are more likely to accept robotic assistance if they are still allowed to directly manipulate the instruments.
“So we developed a tool where both the robot and the surgeon manipulate a single tool together,” says Taylor, referring to the “steady-hand” robots he’s pioneered for microsurgery, which quell the natural tremors of even the surest surgical hand.
The steady-hand robot senses forces exerted by the surgeon on the tool handle and moves to comply with the surgeon’s wishes. The robot performs actual motion. The robot can also enforce safety barriers beyond which the surgical tool cannot go, in order to prevent surgical errors. Taylor refers to these as “virtual fixtures.” The tool can likewise control the amount of force exerted by surgical tools on delicate tissues.
“Steady-hand eliminates the tremors. This can help surgeons perform current procedures and can enable them to perform procedures that are currently impossible for even the most expert surgeons,” Taylor notes.
There is a strong data component running throughout Taylor’s work. Every movement during the surgery is recorded and folded into a database to improve the next similar surgery down the line. This reflects a tight synergy between technology and big data. “Computers can help plan, perform, and verify what’s been done in the operating room,” Taylor says, likening the data capture function of his robots to the black-box flight data recorders found on airplanes.
“We’re capturing data so that the surgeon knows what he or she did,” Taylor says. “You can compare outcomes and improve surgical processes and improve consistency.”
Johns Hopkins ophthalmologist James Handa has worked with Taylor on systems to perform retinal surgery, and he is a true believer. “With Russ, not only have the robots transformed the way we do surgery, but the complete systems that he and the team have developed provide very detailed feedback that allows us to develop a more precise language for describing surgeries,” says Handa, the Robert Bond Welch Professor of Ophthalmology at the Johns Hopkins School of Medicine. “I think this will actually have its greatest benefit in surgical education and evaluation. The average surgeon can become excellent. The excellent surgeon can go where no one has gone before.”
Although Taylor and his colleagues have used the steady-hand concept for many applications—including sinus, brain, ear, and orthopedic surgeries—one of the most challenging environments is the human eye. Retinal surgeries are common to remove scar tissue, lesions, and tumors, or to inject drugs directly into diseased areas that would otherwise be out of reach of pharmaceuticals.
As one might imagine, surgery in the eye is delicate work. The structures of the eye are almost incomprehensibly fragile, minute, and inaccessible. The price of an error is great. The retina does not regenerate. A mistake could cost the patient his or her eyesight.
It takes just 7.5 millinewtons of force to tear the retina, Taylor says, an amount considerably below the amount the human hand can sense. His robots can provide the surgeon with that degree of feel. Likewise, his systems can help the surgeon see better, as well. A typical procedure could involve the removal of scar tissue on the retina, which might be just a thousandth of an inch thick, so small that the surgeon has difficulty even seeing the edge between the membrane and the retina.
“We can sense where that edge is using an optical coherence tomography sensor built into the surgeon’s tools and show him or her where to grasp the edge,” he says. Taylor likens the problem to peeling sticky tape off tissue paper without tearing the paper.
Few surgeons in the world have the dexterity to operate freehand in such an environment. Even the very best surgeons experience some degree of hand tremors, which severely limit
surgical options and slow procedures to a crawl. Even when the surgeon can position an instrument with accuracy, doing so repeatedly and maintaining position for long periods of time become harder every minute a surgery drags on.
“There is a limit of about 50 microns below which microsurgeons cannot insert needles into the small blood vessels of the retina,” Handa says. “The robot can help breach that threshold and also help the surgeon keep the tiny needle inserted for extended periods of time.”