title: Attaining high bending stiffness by full actuation in steerable minimally invasive surgical instruments.
abstract: BACKGROUND
  Steerable instruments are a promising trend in minimally invasive surgery (MIS), due to their manoeuvring capabilities enabling reaching over obstacles. Despite the great number of steerable joint designs, currently available steerable tips tend to be vulnerable to external loading, thus featuring low bending stiffness. This work aims to provide empirical evidence that the bending stiffness can be considerably increased by using fully actuated joint constructions, enabling left/right and up/down tip rotations with the minimum of two degrees of freedom (DOF), rather than conventional underactuated constructions enabling these rotations with more than two DOF.
  
  
  METHODS
  A steerable MIS instrument prototype with a fully actuated joint construction was compared to state-of-the-art underactuated steerable instruments in a number of tip deflection experiments. The tip deflections due to loading were measured by means of a universal testing machine in four bending scenarios: straight and bent over 20°, 40° and 60°.
  
  
  CONCLUSIONS
  The experimental results support the claim that a fully actuated joint construction exhibits a significantly larger bending stiffness than an underactuated joint construction. Furthermore, it was shown that the underactuated instrument tips show a considerable difference between their neutral positions before and after loading, which could also be greatly minimised by full actuation.
authors.affiliation: BioMechanical Engineering Department, Faculty Mechanical, Maritime & Materials Engineering, Delft University of Technology , Delft , The Netherlands.
authors.forename: Filip
authors.initials: F
authors.lastname: Jelínek
authors.forename: Giada
authors.initials: G
authors.lastname: Gerboni
authors.forename: Paul W J
authors.initials: PW
authors.lastname: Henselmans
authors.forename: Rob
authors.initials: R
authors.lastname: Pessers
authors.forename: Paul
authors.initials: P
authors.lastname: Breedveld
mesh_terms: D004548:Elasticity; D004867:Equipment Design; D006801:Humans; D019060:Minimally Invasive Surgical Procedures / Q000295:instrumentation*; D013525:Surgical Instruments
keywords: Minimally invasive surgery; actuation; bending stiffness; deflection; steerable joint