Modular steering mechanism design for cable guidance through reusable minimally invasive instruments

Abstract

Minimally Invasive Surgery (MIS) has made tremendous impact on hospitals worldwide. Introduced as a patient friendly alternative to open surgery by significantly reducing incisions size, benefits such as faster patient recovery time, and less pain for patients, are achieved. However, in MIS, rigid instrument shafts can impair surgeons’ dexterity as access to pathology sites is complicated. Steering mechanisms have been developed to locate and orientate an instrument tip for tissue manipulation. Many steerable Minimally Invasive (MI) instruments are intended for single use only, because the actuation cables in those instruments cannot be properly cleaned. Consequently, costly and well-functioning instruments are disposed after each surgical procedure, forming a burden to both hospital sustainability and financial expenses. A platform technology suitable for reuse is brought to the market by the Delft University of Technology in collaboration with Surge-On Medical B.V. Problems with this platform arise in the integration of an internally routed cable, since a hinge in the steering mechanism leads to a critically small cable bending radius. In the present master’s thesis, a bare minimum design approach is followed to make the platform technology compatible with internally routed cables. Based on set requirements, multiple concepts of steering mechanisms are generated and evaluated. The most promising concept is modelled, tested and validated with computer models and experiments. The final design comprises a four-bar linkage mechanism and an innovative joint is used to kinematically stabilize the mechanism. The mechanism achieves 140 degrees of tip articulation and guides internally routed cables with a bending radius of 5mm. The steering mechanism fits through trocars of 5mm and can support loads of 40N, as applied by internally routed cables. The design can be integrated in reusable minimally invasive surgical instruments, since detachment of components allows for effective cleaning and inspection. The designed steering mechanism can be used as building block for reusable minimally invasive instruments, providing an important step to the next generation of steering technology in MIS.