Real-time measurement of the tool-tissue interaction in minimally invasive abdominal surgery; the first step to developing the next generation of smart laparoscopic instruments

Introduction: Analysis of force application in laparoscopic surgery is critical to understanding the nature of the tool-tissue interaction. The aim of this study is to provide real time data about manipulations to abdominal organs. Methods: An instrumented short fenestrated grasper was used in an in vivo porcine model, measuring force at the grasper handle. Grasping force and duration over five small bowel manipulation tasks were analysed. Forces required to retract gallbladder, bladder, small bowel, large bowel and rectum were measured over 30 seconds. Four parameters were calculated; T (hold) ; the grasp time, T(close); time taken for the jaws to close, F(max); maximum force reached, F(rms); root mean square force (representing the average force across the grasp time). Results: Mean F (max) to manipulate the small bowel was 20.5N (+-7.2N) and F (rms) was 13.7N (+- 5.4). Mean T (close) was 0.52s (+-0.26) and T (hold) was 3.87s (+-1.5). In individual organs mean F (max) was 49N (+-15) to manipulate the rectum and 59N (+-13.4) for the colon. The mean F (max) for bladder and gallbladder retraction was 28.8N (+-7.4) and 50.7 (+-3.8) respectively. All organs exhibited force relaxation, the F (rms) reduced to below 25N for all organs except the small bowel, with a mean F (rms) of under 10N. Conclusion: This study has commenced the process of quantifying tool-tissue interaction. The static measurements discussed here should evolve to include dynamic measurements such as shear, torque and retraction forces and be correlated with evidence of histological damage to tissue.