Needlescopic surgery given dexterity by tiny mechanical wrist

A team of engineers and doctors at Vanderbilt University's Medical Engineering and Discovery Laboratory has developed a surgical robot with steerable needles equipped with wrists with a diameter of 2mm.

Needlescopic surgery, a minimally invasive technique, has been used since the 1990s and uses surgical instruments the size of a needle. The incisions needed to insert the instruments are so small (5 to 10mm) they can be sealed with surgical tape rather than stitches. But, the technique is only carried out by a handful of surgeons as it is so difficult.

The new device is designed to provide needlescopic tools with a degree of dexterity that they have previously lacked. Not only will this allow surgeon-operators to perform a number of procedures such as precise resections and suturing that haven't been possible before, but it will also allow the use of needles in places that have been beyond their reach, such as the nose, throat, ears and brain.

"The smaller you can make surgical instruments the better, as long as you can maintain an adequate degree of dexterity," said Professor of Urological Surgery S. Duke Herrell, who is consulting on the project. "In my experience, the smaller the instruments, the less post-operative pain patients experience and the faster they recover."

The Vanderbilt team's robotic arm is made of nitinol, a 'memory metal' that retains its shape after being bent. As nitinol is a rigid material, ridges were cut into one side of it to allow it to bend up to 90°, operated by a wire-and-pulley system threaded through the inside of the tube.

The team is completing the control software on the device that allows surgeons to operate it and would like to test the system by using it for 'transnasal' surgery, to remove tumours in the pituitary gland or the base of the skull that traditionally involve large incisions in the face or skull.

"It should be useful for a number of other operations as well," added Webster. "Once we give this tool to surgeons they will find all kinds of applications we haven't thought of."