Design, Analysis and Experimental Validation of a Novel 7-Degrees of Freedom Instrument for Laparoscopic Surgeries.

Laparoscopic surgery is widely used for treating intra-abdominal conditions involving the gallbladder, pancreas, liver, intestines and reproductive organs. Conventional laparoscopy instruments used in manual surgeries usually have straight shafts and four degrees of freedom (DOF) plus grasping. However, these are insufficient for the complete rotation of the instrument tip. This makes it challenging to access difficult-to-reach organs inside the abdomen during the surgeries. A few robotic instruments available in the market have higher maneuverability but are expensive. Instruments incorporating cable-based mechanisms require replacement after a few sterilization cycles. This paper describes a novel, reusable and affordable multi-DOF laparoscopy instrument that provides two additional DOF: (a) wrist articulation about one axis (wristed yaw) and (b) rotation of the jaw after articulation (jaw roll). The wrist can articulate up to 45° and also roll after articulation. The additional degrees of freedom enable better maneuverability, functionality and reach than conventional laparoscopy instruments. Further, the new instrument employs only rigid links, providing better strength and minimal loss of function after multiple sterilizations. The complete design of the novel instrument, followed by its kinematic analysis and force calculations are explained in this paper, concluding with its manufacture and experimental validation.