Design, Analysis, and Experimental Evaluation of a Novel Three Fingered Endoscopic Large Organ Grasper

Abstract

The currently available laparoscopic instruments are unable to manipulate and grasp the large intraabdominal organs, such as spleen and kidney, with sufficient stability and safety. This paper describes a novel threefingered endoscopic instrument, based on parallelogram mechanism, which can fully constrain the large organs and provide an effective grasping function. We first evaluated the efficacy of the design using a 3D model and finite element analysis. Then, a fully functional prototype was fabricated for experimental evaluations, including force propagation and pull force limitation characteristics. Finally, the instrument's capability for effective grasping was investigated on animal specimens in in vitro and in vivo examinations. The results of the force propagation analysis indicated a high amplification ratio of more than 1.2 for the actuating force when grasping large organs. The pull force experiments on a sheep heart specimen revealed a nearly linear relationship between the actuating force and the limit of the pulling force that could be attained without slippage. The resulting pinch force, however, was found to be injurious if the actuating force exceeded a limit of 8.6 N. The in vitro and in vivo examinations of the instrument indicated its capability to pass through a standard 10mm trocar to enter the abdomen, open its fingers to a diameter of about 80 mm, and grasp and manipulate organs with different sizes, shapes, and properties. With further developments, the proposed design is expected to provide a practical and feasible solution for grasping of large organs during endoscopic operations. However, more preclinical examinations are needed to evaluate the potential risks of using rigid jaws against injuryprone soft organs.