DragonFlex Smart Steerable Laparoscopic Instrument

Abstract

Despite its success, e.g., in prostatectomy, da Vinci's steerable grasper EndoWrist from Intuitive Surgical has a complex design prone to steel cable fatigue, potential sterilization issues and high associated costs, all of which insinuate a need for an alternative. The aim of this paper is to demonstrate a design of a structurally simple handheld steerable laparoscopic grasping forceps free from cable fatigue, while attaining sufficient bending stiffness for surgery and improving on EndoWrist's maneuverability and dimensions. Having equal joint functionality to EndoWrist, DragonFlex's instrument tip contains only four parts, driven and bound by two cables mechanically fixed in the handle. Two orthogonal planar joints feature an innovative rolling link mechanism allowing the cables to follow circular arc profiles of a diameter 1.5 times larger than the width of the instrument shaft. Besides maximizing the cable lifespan, the rolling link was designed to equalize the force requirements on both cables throughout joint rotation, making the handling fluid and effortless. The smart joint design and stacked instrument construction enable control of seven degrees of freedom by only two cables and seven instrument components in tip, shaft and handgrip altogether. Two DragonFlex prototypes were developed by means of additive manufacturing technology, allowing grasping and omnidirectional steering over ±90 deg, exhibiting promisingly high bending stiffness and featuring extreme simplicity at 5 mm dimensions. DragonFlex concept sheds new light on the possibilities of additive manufacturing of surgical instruments, allowing for a feature-packed design, simple assembly, suitability for disposable use and potential MRI compatibility.