Collaborative Research: Understanding Dynamic Behaviors of Tissue Welding for High Quality Electrosurgical Tissue Joints

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Tissue welding, also known as electrosurgical joining of tissues, is a process used in surgery to seal blood vessels in order to control bleeding. It uses a combination of electro-resistive heating and mechanical clamping to elevate tissue temperature and denature collagen, such that separate tissue can be reconnected. Tissue welding is becoming more prevalent because of the increasing use of minimally invasive surgical procedures, where only a few small incisions are made to access the surgical site. In these cases, it is difficult to use the traditional hand suturing technique to seal wounds because of limited accessibility. There are more than 1.5 million surgical procedures done in US annually that involve the tissue welding process. The overall market size for electrosurgical devices is more than 1 billion dollars in US in 2011 and is increasing by 5-6 percent each year. Despite its importance, the quality of tissue welding joints is often inconsistent due to the lack of good understanding and proper quality control of the tissue welding process. Failed joints can cause severe bleeding, prolonged operative time, and impaired surgical outcomes. This research will lead to more consistent and reliable tissue joints, thus improved healthcare safety and quality. It will also lead to the advancement of electrosurgical tools for tissue welding, and increase the competitiveness of US medical device manufacturing. The research team will study the dynamic behavior of tissue's thermal and electrical impedances during the tissue welding process and to correlate these behaviors to the joint strength. The tissue thermal and electrical impedances will be experimentally determined at different levels of thermal dose. The results will be used to develop a multi-physics finite element model to predict spatial and temporal temperature distribution of the joint site from the electrical energy input. The effect of clamping force on the contact area between the electrosurgical tool and tissue will be explored. A series of tissue joints using various levels of thermal dose and mechanical clamping force will be conducted and the strength of these joints tested to establish a weld quality prediction model. The fundamental understanding obtained from this research on biological material responses to heat will find many applications in other surgical processes, such as laser and ultrasonic tumor ablation.