Force sensor for laparoscopic surgical instrument

INTRO: A force sensor has been designed to fit on existing laparoscopic instruments in order to provide visual and auditory information to replace the sense of touch that has been lost through laparoscopy. A three phase experimental trial using a porcine model has been completed to test the hypothesis that force information can be used to minimize tissue trauma during laparoscopic surgery. The first phase provided force threshold values to evaluate the limits of force which could be applied to tissues during surgery. The second phase, which is the subject of this presentation, attempted to determine if increasing lbs. of force correlated with increasing tissue trauma in vivo. The third phase provided a clinical correlation for this information. METHODS: A pneumoperitoneum was established in 7 pigs. Using laparoscopic techniques, a method of traction-countertraction was used to secure areas of small bowel, while a force of 1.2 lbs., 0.6 lbs., and 0 lbs. (grasping force alone) were applied in series with the force sensing instrument. Twelve applications of each level of force were performed, in different areas of small bowel. Each area of traumatized bowel was marked with staples, the animals closed, and 48 hours later the bowel was resected. Each area of trauma was marked with India ink and 10 slides were made (total of 360 slides per pig). The level of trauma for each area was quantified microscopically by recording depth of inflammation, necrosis, and amount of fibrin deposition. Two analyzers blindly examined the specimens and graded the tissue damage. RESULTS: A total of 360 slides per pig were reviewed by both analyzers. The results were then correlated with the amount of force applied. Tissue trauma was found with both traction forces (0.6 lbs. and 1.2 lbs.), as well as grasp force alone (0 lbs.) Using ANOVA analysis, preliminary results confirm our hypothesis that there is a linear relationship between the force that is applied to a tissue and the degree of trauma produced. CONC: These results provide evidence that small forces applied to tissues can cause significant trauma. By providing feedback information to the surgeon about his/her degree of force being applied to tissues, this force sensor may limit tissue damage as well as provide an alternative to tactile information for the surgeon in training.