“Can we make robots that live and work inside the body?” biomedical engineer Pierre Dupont asked almost a decade ago when he began work at Boston Children’s Hospital, where he is now Chief of Pediatric Cardiac Bioengineering. The answer, we’re learning, is yes. A new study in pigs suggests that an implanted motor may be able to treat babies with malformed esophagi, a devastating condition that is currently treated through invasive, weeks-long medical procedures. The hope is that, with robots, this could become unnecessary in the future.
A study published on Wednesday in Science Robotics found that a robotic implant can be used to induce esophagus growth in pigs. Essentially, the robot stretched the esophagus until it begins to grow back together. While treating patients in a similar way is still science fiction, this is a step towards one day using robotic implants in humans to induce similar growth. At least, that is the researchers’ goal.
Dupont, one of the paper’s authors, said that he has always been interested in using robots in a healthcare setting. He quickly found a worthy cause: long-gap esophageal atresia, a birth defect in which babies are born with a gap in their esophagus greater than three centimeters.
“Think if you went to drink a glass of water and your esophagus just ended,” Dupont said. The disease occurs in one in 4,000 babies, and is fatal unless treated. The mortality rate is fairly low, though, when treated with the Foker process, a complex surgery used when the gap in the esophagus is too large to sew the ends together. Instead, surgeons tie sutures around each end of the esophagus and pull the sutures down to the child’s back in separate “buttons.” They can then be tightened, bit-by-bit, everyday, until the esophagus heals on its own.
This technique has been very useful in treating the condition, with a 95 to 100 percent success rate, but it has its drawbacks: The baby must stay in the hospital for over three months and must be paralyzed for around two weeks for it to work, Dupont said. On top of that, the expense is enormous, at over a million dollars.
With the robotic implant, surgeons wouldn’t need to paralyze and sedate the babies.
“You will eliminate all the risks of long-term anesthesia. For kids, anesthesia isn’t great anyway,” Dupont said. “You just don’t know what it’s doing to their neurocognitive development when you have them out for so long.”
The robotic implant also would also allow the procedure to be tailored to different patients, as well as greater precision and control over the process.
The robotic implant that Dupont and his co-authors designed basically works like this: A battery-powered motor is attached to two rings that are sewn around the esophagus. The motor is connected via cable to a controller on the back of the animal (pig or, in the future, human), allowing the researchers to control the amount of force applied to the esophagus, pulling the lower ring away form the upper ring to lengthen the esophagus a little bit at a time.
This is a process called mechanostimulation, in which applying traction, or a pulling force, induces tissue growth. Dupont said that mechanostimulation is not fully understood but widely exploited. (One application, often used for breast reconstructions, is known as a tissue expander, in which doctors insert balloons under the skin, stimulating skin growth.)
Once the researchers developed the device, it was implanted in five pigs, with three remaining robot-free as a control, all eight with healthy esophagi. The robot then increased the distance between the rings a small amount each day, as per the researchers’ instructions. The pigs did not show any signs of discomfort, and had normal appetites even after surgery, according to the study.
After eight or nine days of pulling, depending on the pig’s schedule, the researchers were able to show 77 percent growth, a statistically significant response in comparison to controls. This was true even despite the small number of test subjects.
Dupont and his co-authors also found an increase in cells in the esophagus, which indicates that the traction force stimulated growth, and not just stretching. It’s like a rubber band between your fingers that not only stretches in response to pulling, but also grows so that the bands remain just as thick as when relaxed.
The researchers found that the newly-grown tissue was functional. The affected part of the esophagus showed at least some peristalsis, the muscle contractions down the esophagus that allow animals (including humans) to swallow food.
Looking toward the future, Dupont wants to extend the applications of the implant to treat short bowel syndrome, a condition in which children born with a complete bowel get an infection, causing so much bowel to be removed that the children often cannot absorb nutrients properly and are fed intravenously.
Devices designed to treat rare illnesses like esophageal atresia are difficult to commercialize, so Dupont hopes that the robot implant can prove itself multi-use, and will be available for treatment of short bowel syndrome and other conditions involving defects in tubular organs.
With this study, robotics have come that much closer to becoming a standby of medical treatment. All illnesses, including rare ones, deserve a robot helper if they can get it.
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