Abstract
PurposeThe introduction of novel endoscopic instruments is essential to reduce trauma in visceral surgery. However, endoscopic device development is hampered by challenges in respecting the dimensional restrictions, due to the narrow access route, and by achieving adequate force transmission. As the overall goal of our research is the development of a patient adaptable, endoscopic anastomosis manipulator, biomechanical and size-related characterization of gastrointestinal organs are needed to determine technical requirements and thresholds to define functional design and load-compatible dimensioning of devices.MethodsWe built an experimental setup to measure colon tissue compression piercing forces. We tested 54 parameter sets, including variations of three tissue fixation configurations, three piercing body configurations (four, eight, twelve spikes) and insertion trajectories of constant velocities (5 mms−1, 10 mms−1,15 mms−1) and constant accelerations (5 mms−2, 10 mms−2, 15 mms−2) each in 5 samples. Furthermore, anatomical parameters (lumen diameter, tissue thickness) were recorded.ResultsThere was no statistically significant difference in insertion forces neither between the trajectory groups, nor for variation of tissue fixation configurations. However, we observed a statistically significant increase in insertion forces for increasing number of spikes. The maximum mean peak forces for four, eight and twelve spikes were 6.4 ± 1.5 N, 13.6 ± 1.4 N and 21.7 ± 5.8 N, respectively. The 5th percentile of specimen lumen diameters and pierced tissue thickness were 24.1 mm and 2.8 mm, and the 95th percentiles 40.1 mm and 4.8 mm, respectively.ConclusionThe setup enabled reliable biomechanical characterization of colon material, on the base of which design specifications for an endoscopic anastomosis device were derived. The axial implant closure unit must enable axial force transmission of at least 28 N (22 ± 6 N). Implant and applicator diameters must cover a range between 24 and 40 mm, and the implant gap, compressing anastomosed tissue, between 2 and 5 mm.
Highlights
Since the last 15 years, current research efforts focus on enabling endoscopic interventions within the access lumen itself, and on other organs of the abdominal cavity
We investigated whether different fixation point arrangements, amounts of tips, as well as varying insertion speeds and accelerations of the implant influence insertion force and process
Stress applied to the tissue, and measured force, rises with increasing piercing body displacement, respectively, time
Summary
Since the last 15 years, current research efforts focus on enabling endoscopic interventions within the access lumen itself, and on other organs of the abdominal cavity. Biomechanical characterization of gastrointestinal organs is needed to determine technical requirements and thresholds that define the functional design and load-compatible dimensioning. This includes the assessment of sizerelated anatomical properties for dimensioning scalability with respect to lumen diameter and bowel wall thickness. Focus of the present study was to develop a system to reliably assess tissue penetration forces and the investigation of geometrical characteristics. By application of this innovative test rig, we were able to examine various implant- and applicator-related design specifications and their impact on puncturing forces
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