Tiny Mechanical Wrist Advances Needlescopic Surgery

Developed by researchers at Vanderbilt University (Nashville, TN, USA) the new wrists are less than 2-mm thick, and are designed to provide needlescopic tools with a degree of dexterity previously lacking. Not only will this allow surgeon-operators to perform a number of new procedures (such as precise resections and suturing that have not been possible previously), but it will also allow the use of needles in places that have so far been beyond reach, such as the nose, throat, ears, and brain.

Needlscopic concentric tube robots are based on a series of telescoping tubes made of nitinol. Each of the tubes has a different intrinsic curvature; by precisely rotating, extending, and retracting the tubes, an operator can steer the tip in different directions, allowing it to follow a curving path through the body. The design allows the needles to operate in areas of the body that neither manual endoscopic instruments nor the da Vinci robot can reach. However, the usefulness of concentric tube robots was limited by the fact that the needles didn’t have a wrist.

The researchers therefore developed a wrist that also consists of a nitinol tube, but with several asymmetric cutouts. Pulling on an actuation tendon that runs through it causes the tube to bend by up to 90 degrees; when tension on the tendon is released, the tube springs back to its original shape. The researchers mounted a curette on the tiny (1.16 mm) wrist, and succeeded in bending it in various directions. The study describing the new wrist was presented at the annual International Conference on Robotics and Automation, held during May 2015 in Seattle (WA, USA).

“Adding the wrists to the steerable needles greatly expands the system’s usefulness. There are a myriad of potential applications in some really exciting areas such as endoscopic neurosurgery, operating within small lumens such as the ear, bronchus, urethra, etc.,” added professor of urological surgery S. Duke Herrell, MD, who is consulting on the project. “This would allow us to do surgeries that at present require much larger incisions and may even enable us to perform operations that are not feasible at present.”

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