Steerable and Reusable Bipolar Vessel Sealer

Abstract

A new radical design approach arose from the need to develop a bipolar electrosurgical instrument that is modular and cleanable, thus reusable and therefore suitable for low- and middle-income countries (LMICs). Advanced Bipolar Vessel Sealer (BVS) instruments that are currently on the market cannot be cleaned or maintained well and are therefore most often sold as disposables. Especially in LMICs it is a significant financial burden for hospitals. This possibly leads to the re-use of single-use intended instruments which in turn jeopardizes patient safety. Simultaneously, designing a reusable instrument fits well in the transition to a more circular and sustainable society. To perform advanced laparoscopic surgery with cleanable and affordable electrosurgical instruments, a new design approach is needed. A first phase was initiated by the creation of a cable less steering principle called Shaft Actuated Tip Articulation (SATA) mechanism [6]. Unfortunately, by adding electrically conductive wires to a SATA instrument it loses its modularity and thus cleanability, precisely for which the SATA technology offered a solution in the first place. In addition, there are no non-robotically controlled and reusable BVS instruments with two DOFs available on the market. By being steerable, the user of the instrument is able to deliver a higher quality seal as well as to seal more difficult-to-reach blood vessels and tissue. In this thesis project the goal is to redesign a SATA instrument which sustains bipolar vessel sealing and thus designing a BVS that is easy to clean, easily disinfected and sterilized and which is reusable for a vast amount of surgical procedures. Ideas have been gained by analysing the SATA mechanism and studying commonly used BVS devices. A systematic selection procedure based on the design requirements has resulted in a winning concept for the conduction of electricity through the SATA instrument. For the design of the tip, determining factors were elaborated on, including the construction of the open and close mechanism and the force transmission ratio between the required seal force on the blood vessel or tissue and the necessary tensile force in the core of the instrument. The most critical components of the final model have been identified and evaluated by means of FEM simulations and an experiment. The FEM simulations of the tip components show that the design is satisfactory and that a safety factor of ~1.5 has been achieved. This means that these components do not fail due to normal use and they have a long lifespan as well. In the experiment a flexible nitinol guidewire with Teflon coating was tested for wear by pulling the guidewire through an angled SATA hinge. After some necessary adjustments and additions to the design of the BVS, the results were improved but not optimal. The outcome of this project is a good basis for the BVS design where the steerability has been maintained as well as the modularity and cleanability. The reusability depending on the flexible coating around the core needs to be further investigated and improved.