Evaluating temperature and duration in arterial tissue fusion to maximize bond strength

Tissue fusion is a growing area of medical research that enables mechanical closure of tissues without the need of foreign bodies such as sutures or staples. Utilizing heat and pressure applied for a specified time, a bond can be formed between adjacent tissues. The success or failure of tissue fusion is contingent upon the strength of the bond it creates between opposing tissues, yet little characterization has been done to measure the strength of this interface as a function of the input parameters, such as heat and pressure. Previous studies have examined the strength of tissue fusion using clinically relevant outcomes such as bursting pressure or tearing strength, but none have explored metrics more appropriate for determining the mechanics of the actual bond such as peel or shear strengths. The goal of this study is to establish methodology for T-peel and lap shear testing of fused tissues and measure the fusion bonding strength as a function of temperature and time using the ConMed Altrus(®) laparoscopic thermal fusion device. Across five temperatures (120, 140, 150, 160, 170°C) and four time durations (500, 1000, 1800, 3000ms) the mean peeling strength, ultimate shear strength, and bursting pressure of fused porcine splenic arteries were measured. The shear strength increased with increasing temperature and time with an ultimate shear strength at 160°C and 3000ms equal to 290 ± 99Pa. No trend was observed between the input parameters of time and applied temperature and the mean peeling force, although there were significant differences between groups. The bursting pressure increased significantly with increasing durations, but no trend was noted between temperature and bursting pressure. The shear strength data suggest there is some physical or chemical reaction which occurs in the tissue between 120°C and 150°C which provides a stronger bond. The shear and peel results also reveal that the fusion bond undergoes brittle failure. This study suggests that the tissue fusion bond is maximized at temperatures over 150°C and at a time of 3000ms using the ConMed Altrus(®) and that input parameters can be tuned to optimize the strength of the bonded region.