The design, production and validation of a force limiting mechanism in a laparoscopic instrument

Laparoscopic surgery uses small incisions and a camera for abdominal or pelvic operations, with benefits such as shorter recovery time and hospital stay. However, reduced surgeon hand-eye coordination and feedback can lead to excessive applied force and potential tissue damage. Haptic and visual feedback systems have been developed for laparoscopic surgery, and their benefits for various laparoscopic tasks have been demonstrated. Although force feedback systems have been extensively studied, there is a dearth of research on force limiting mechanisms in laparoscopic surgery. Nonetheless, incorporating force limiting mechanisms could help prevent complications caused by excessive applied force by the user. This paper presents the design, production and validation of a force limiting mechanism in a laparoscopic instrument, to prevent tissue damage due to excessive applied force by the surgeon. A design method was conducted, which comprised a functional analysis and a design process. Subsequently, a force limiting mechanism was designed and manufactured using various techniques. To validate the mechanical performance, the force in the forceps Fpinch and the force in the rod Frod of the laparoscopic instrument were measured. This was carried out under three conditions with the force limiting mechanism set at 10 N, 20 N, and 40 N for Fpinch. To validate pre-clinical performance, twenty novices performed a crossover study. Participants performed a basic laparoscopic task by grasping a Floral foam object under two conditions: with and without the force limiting mechanism. The relative depth and the slippages of the Floral foam object was computed after each trial. The mechanical validation results showed that for the instrument with the force limiting mechanism, Fpinch remained constant at 0.5 N and 2.0 N, while Frod increased. The pre-clinical validation revealed a significant difference in relative depth between the two instruments. The laparoscopic instrument with the force limiting mechanism was superior compared to the laparoscopic instrument without the force limiting mechanism (p<0.001), as less force was transferred by the force limiting mechanism. Additionally, no difference was found between the two instruments in slippages (p=0.068). It can be concluded that a force limiting mechanism in a laparoscopic instrument has been successfully designed and validated and can prevent tissue damage by blocking the excessive applied force by the surgeon. However, further improvement is required to overcome limitations in the design. Moreover, the design has to be tested in various (pre-)clinical settings in order to improve the validity and reliability of the design. Additionally, implementing the force limiting mechanism in robotic surgery should also be considered. Mechanical Engineering | BioMechanical Desig