A variable stiffness mechanism for minimally invasive surgical needles

Needles are instruments frequently employed in Minimally Invasive Surgery (MIS), and are especially requested in percutaneous diagnosis and in local therapies [1]. During procedures, tissue inhomogeneity, tissue deformation, and thus needle deflection can cause tip misplacement resulting in inaccurate anesthesia, repuncturing with additional damages of the tissue or false negative detection [2]. Previous studies focused on needle-tissue interaction and possibilities to improve the needle steerability [3]. The proposed work is aimed to design a new concept of needle based on variable stiffness able both to balance tissue inhomogeneity and to guarantee needle steering during the insertion. The structure of the Variable Stiffness Mechanism (VSM) allows the needle to adjust the deflection when passing through tissues, while the omnidirectional steering of the tip facilitates the achievement of the target.