Smita De (BioRobotics Lab)
Department of Bioengineering (Doctoral Student)
"Measurement of Tissue Damage Due to Mechanical Stresses During MIS"


ABSTRACT

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.  This creates the potential for excessive force application during surgery that can result in clinically relevant consequences.  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 increase patient safety.  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.  Finite element analysis provided estimations of the stress distributions between the grasper jaws, allowing for more accurate correlations of damage to stress.  ANOVA and post-hoc analyses were used to detect stress magnitudes and durations that caused significantly increased tissue damage.  Preliminary data show a graded non-linear response between applied stress magnitude and apoptosis in liver and small bowel as well as granulocyte infiltration in small bowel.  These results suggest that this methodology is appropriately sensitive for the ultimate goal of identifying damage ‘thresholds’ and stress dose response curves for multiple organs during grasping.