Objective: To study temperature distribution in different electrodes and to evaluate thermal spread during colonic anastomosis induced by radiofrequency energy through finite element modeling, aiming to provide the basis for optimizing the design of new electrodes with improved effectiveness of electrosurgical welding.

Methods: Three electrodes with the feature of concave-convex (CC), rail coupled concave-convex (rail-CC), and cross rail coupled concave-convex (cross rail-CC) were designed for radiofrequency-induced serosa-to-serosa colonic anastomoses to evaluate the thermal spread process by finite element modeling using COMSOL Multiphysics. Parameters used in the modeling were set with a peak voltage of 45 V, a duty cycle of 10% and a repetition rate of 1 s. Additionally, a three-dimensional finite element model of the cross rail-CC electrode was further constructed to compare temperature variation and distribution when the voltage Fwas applied to ridges of upper electrode alternately.

Results: The electrode with CC design produced similar temperature between 'gap' and 'compressed' areas, whereas the electrode with rail-CC design exhibited the highest temperature at 'gap' and 'compressed' areas compared with those with CC and cross rail-CC designs. Moreover, the cross rail-CC electrode, by tightly occluding the upper and lower electrodes, could create uniform compression and temperature variation. When electric voltage was applied to ridges of upper electrode of the cross rail-CC electrode alternately, the temperature at 'gap' was half of that at the 'compressed' section, which was comparable to the temperature at 'compressed' area in the rail-CC electrode (p=0.241).

Conclusion: Alternating application of voltage to ridges of upper electrode of the cross rail-CC electrode can potentially produce an optimal fusion zone by reducing thermal damage with low 'gap' temperature while keeping the 'compressed' temperature high.