Force Transmission at Flexible Endoscopy with Conventional Endoscopes and Shape Locking Endoscope Guide Catheter

Abstract

Background: A major limitation to the development of flexible endoscopic surgery is the limitation of force, which can be exerted on needles, catheters and endosurgical surgical instruments in a forwards and sideways direction. The flexibility of the endoscopes and the instruments passing through them reduces precision and control when compared with rigid surgical instruments. Aim: To compare the forces exerted by instruments during endosurgical maneuvers through flexible endoscopes and using shape-locking technology (SLT). Methods: We compared forces exerted pushing needles through tissue using 1: flexible endoscopic grasping forceps holding a threaded needle, 2: needles of 21,19,17 Guage, 3: stents of 5, 7, 10, F over a guide wire which were passed through the wall of a porcine stomach. Studies were performed on the bench with postmortem tissue and were then in live experiments. Push, pull and lateral force were measured with a force gauge. Measurements (n=10 each) were made using instruments in postmortem pig stomach passed through a gastroscope (Olympus 140) and the same gastroscope constrained in SLT guide catheter SG1. Results: In live pig studies, maximum pushing force exerted on the wall of the stomach by forceps passed through the accessory channel of an endoscope in a live pig stomach held at an intragastric angle of 90 degrees(d) was 94.9 grams. When the SLT catheter was locked over the endoscope the force was increased to 431 grams (365% increase in force). Pull force in the opposite direction again at 90d to the cephalad-caudad axis of the animal was 281 without and 691 grams with SLT (146% increase) (p<0.05). Peak pushing force of the endoscope, positioned in the duodenum in a live pig with a 90d turn into duodenum after entering the pylorus) was 470 without and 1094 grams with the shape locking technology (135% increase in force) (p<0.05). SLT allowed the passage of stents, and needles through the wall of the unsupported stomach which could not be accomplished without. Conclusions: The forces exerted at flexible endoscopy, especially push and lateral 90 degree force were substantially reduced compared with laparoscopic instruments. Lateral force was very limited when using flexible biopsy forceps through flexible endoscopes. Using SLT to restrain the flexible endoscope, a four-fold increase in pushing force was measured. This allowed endosurgical maneuvers to be accomplished, which could not be performed by conventional flexible endoscopes alone.