Defining the Relationship Between Stress from Laparoscopic Graspers and Bowel Injury in Humans to Establish Intraoperative Force Boundaries

Amanda Khan (1, 2), Matthew MacDonald (2), Catherine Streutker (3, 4), Corwyn Rowsell (3, 4), James Drake (1, 2, 5),

Institute of Biomaterials and Biomedical Engineering, University of Toronto, 2) Centre for Image Guided Innovation and Therapeutic Intervention, Sick Kids Hospital, 3) Division of Pathology, St. Michael’s Hospital, 4) Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, 5) Division of Neurosurgery, Hospital for Sick Children, Toronto

Standard laparoscopic graspers are used in minimally invasive surgery (MIS) to primarily lift and mobilize delicate anatomical tissues for better visualization and access of the operating field. Serious iatrogenic complications from the use of graspers in bowel surgery includes bowel perforation, serosal tears and post-operative adhesion formation. Bowel perforation is an especially severe intraoperative injury because it is associated with a high morbidity and mortality rate (as high as 3.6%) but its incidence is entirely due to intraoperative error from the misuse of graspers. This study aims to address this concern by investigating the relationship between grasper jaw forces and human small and large bowel (colon) tissues. To this end, the authors of this paper created a custom compression device called the Precision Crush Apparatus for Tissue to ‘grasp’ human bowel tissue with force ranging from 0 to 600 kPa, which corresponds to a typical range of intraoperative grasper force. In total, 8 human colon samples were tested for a total of 48 experimental cases. Two pathologists who were completely blinded to study conditions graded cellular damage and measured serosal layer thickness in the area of compression vs a local control. There was a clear trend that as pressure increases, the trauma to the tissue increased as well. Starting at 300 kPa, the majority (71.4%) of patients’ bowel tissues experienced at least minor damage. At 400 kPa of pressure, that number increased to 100% as all patients were graded with at least a trauma score of 1. At 500 kPa, 20% of patients’ bowel tissues were rated with a trauma score of 2, indicating significant damage. In regards to serosal tissue deformation, at pressures of 100 and 200 kPa, there was no significant deformation (p≥0.05). At 300 kPa, there is a mixed picture of significance as 57% patients had significant p-values. At 400 kPa, 75% of patients experienced significant deformation. At 500 and 600 kPa all patients have significant p-values ≤0.05. Our data shows significant serosal thickness change occurring at 300 kPa for the colon, which also correlated to a marked increase in Trauma Score by the pathologists. Using our logistic regression analysis, our data points in the direction of establishing a maximum force cut-off starting at 275-330 kPa on average for gastrointestinal tissues using a 50% threshold, however very large safety margins should be considered and used.