Assessment of Tissue Damage due to Mechanical Stresses

While there are many benefits to minimally invasive surgery, force feedback, or touch sensation, is lacking in the currently available MIS tools, including surgical robots, creating the potential for excessive force application during surgery. The goal of this work was to develop a methodology with which to identify stress magnitudes and durations that can be safely applied with a grasper to different tissues, helping to improve MIS device design and reduce potential for clinically relevant consequences. Using the porcine model, stresses typically applied in MIS were applied to liver, ureter, and small bowel using a motorized endoscopic grasper. Acute indicators of tissue damage including cellular death, activation of the coagulation cascade, and infiltration of inflammatory cells were measured using histological and image analysis techniques. ANOVA and post-hoc analyses were used to detect stress magnitudes and durations that caused significantly increased tissue damage with the goal to ultimately identify safe stress ´thresholds´ during grasping of the studied tissues. Preliminary data suggests a graded non-linear response between applied stress magnitude and apoptosis in liver and small bowel as well as granulocyte infiltration in small bowel