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A tiny mechanical wrist from a team of engineers and doctors at Vanderbilt University’s Medical Engineering and Discovery Laboratory will be used on needle-sized surgical robots. The wrist is less than 1/16th of an inch (2 mm) thick.

The new device provides needlescopic tools with an improved degree of dexterity. Surgeon-operators will be able to perform a number of procedures that have not been possible before, such as precise resections and suturing. The needles can also be used in parts of the body that have been beyond their reach, such as the nose, throat, ears, and brain.

For the past six years, Professor Robert Webster and his team have developed the surgical robot that uses “steerable needles.” The system of telescoping tubes are made out of nitinol, a “memory metal” that retains it shape.

Each tube has a different intrinsic curvature. By precisely rotating, extending, and retracting the tubes, an operator steers the tip in different directions, allowing it to follow a curving path through the body. Adding the wrists to the steerable needles greatly expands the system’s usefulness.

By cutting a series of tiny slots down one side of the tube, the rigidity decreases substantially. The tube then bends up to 90 degrees by pulling on a small wire running inside the tube. When tension on the wire is released, the wrist springs back to a straight position.

Team members would like to test the system by using it for “transnasal” surgery: operations to remove tumors in the pituitary gland and at the skull base that traditionally involve cutting large openings in a patient’s skull and/or face. Studies have shown that using an endoscope to go through the nasal cavity is less traumatic.

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