THEY don’t drink, they don’t get tired and they don’t go on strike. To hospital managers, the idea of robots operating on patients without human intervention is an attractive one. To patients, though, the crucial question is, “are they better than human surgeons?” Surgery is messy and complicated. A routine operation can become life-threatening in minutes.

Such considerations have meant that the role of robots in operating theatres has been limited until now to being little more than motorised, precision tools for surgeons to deploy—a far cry from the smart surgical pods and “med-bays” of science fiction. But a paper published this week in Science Translational Medicine, by Peter Kim of the Children’s National Health System in Washington, DC, and his colleagues, brings the idea of real robot surgeons, operating under only the lightest of human supervision, a step closer. Though not yet let loose on people, it has successfully stitched up the intestines of piglets.

To build their robodoc, dubbed the Smart Tissue Autonomous Robot (STAR), Dr Kim and his team fitted a robotic arm with an articulated suturing tool and a force sensor to detect the tension in the surgical thread during the operation. They equipped the arm with cameras that could create a three-dimensional image, to guide it as it deployed the tool, and also a thermal-imaging device to help distinguish between similar-looking tissues. A computer program written by the team controlled the arm. This had a repertoire of stitches, knots and manoeuvres that permitted it to plan and carry out a procedure, known as anastomosis, which involves sewing together two parts of a bodily tube.

No pig in a poke

Before each of the trial operations, the team anaesthetised a piglet and opened its abdomen to expose part of its small intestine. They then severed this and highlighted pertinent areas with fluorescent dye, to help guide the arm. Under a surgeon’s supervision, STAR sewed the piglet’s gut together again. In the four operations reported in the paper it carried out about 60% of the procedure without human intervention, and the rest with only minor adjustments to its stitches. Since the team submitted their results for publication, however, they say STAR has successfully completed the entire process unaided.

Comparing STAR’s work with that of experienced surgeons operating both with and without the assistance of existing robotic tools, Dr Kim and his colleagues reckoned STAR’s stitches were more evenly spaced and the sutured gut less leaky. None of the pigs suffered complications.

STAR did, it is true, take much longer than a human surgeon would to create the suture. It averaged 50 minutes for the operation, whereas a person would take about eight. But that will surely get faster. And even if STAR never quite matches a human being at work for speed, the better final product it seems to deliver would, if translated into regular clinical practice, reduce readmission rates.

For now, STAR remains a tool rather than a truly autonomous agent. But such autonomy is probably not far away. Dr Kim hopes, for example, that a souped-up version will soon be able to remove an appendix without any assistance from doctors.

STAR’s existence does, though, highlight two questions being raised more and more in what is an increasingly robotised society. These are: “will people trust robots with their lives?” and, “who is liable if something goes wrong?”

The answer to the first will probably depend on the level of supervision the machines are subject to. It would not take much, for example, to turn airliners into drones, but passengers are reassured by the presence of a flight crew, so this is unlikely to happen soon. The same will probably be true of surgical robots, however good they become. In answer to the second, the lawyers are already circling. Intuitive Surgical, a maker of surgical robots based in Sunnyvale, California, has been on the receiving end of lawsuits alleging (which the firm denies) that surgeons were inadequately trained to use its machines or that the robots were defective. Machines may get the better of humans in the operating theatre, but the courtroom will also determine how fast they spread.