Novel concave–convex electrode for colonic anastomoses by radiofrequency thermo-fusion

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Successful vascular sealing by radiofrequency (RF)-induced tissue fusion is well established. The present study reports on a novel electrode structure design together with its experimental assessment for RF thermo-fusion of porcine colonic segments. Two types of electrode were constructed and used in the present study: one with a conventional smooth surface (S) and the other with a novel reciprocating concave-convex (CC) configuration. Finite element modeling was used to study the thermal distribution profile of the CC electrode. Ex vivo porcine colonic segments were used to create end-to-end serosa-to-serosa colonic anastomoses by applying a pulse of 160 W RF power for 20 s. Different compression pressures (S1, S2, S3) and (C1, C2, C3, C4, C5), were applied, via specially designed ring carriers, to the S and CC electrodes, respectively. Assessment was based on anastomotic burst pressures and histological appearances using light microscopy of paraffin sections. In total, 22 RF-induced circular anastomoses were performed. Similar burst pressures were observed for anastomoses created by the two types of electrodes (S, CC) performed under the same compression pressure. In contrast, significant differences were observed on histological examination of tissue anastomotic site. In particular, fusion areas between gaps of the CC electrode showed normal histological appearance, while the S electrode produced a completely flat featureless appearance. Furthermore, the CC electrode produced significantly different burst pressures depending on the applied compression pressure during thermo-fusion: compression pressures C1 vs. C4 produced circular anastomotic fusions with burst pressures of 21.9 ± 9.3 vs. 44.6 ± 8.9 mmHg, (p = 0.034); but the burst pressure beyond C4, declined significantly, with C4 vs. C5, burst pressures of 44.6 ± 8.9 vs. 24.7 ± 8.0 mmHg, (p = 0.034). The CC electrode exhibits larger and faster thermal diffusion profiles resulting in normal histological appearances in the gaps between CC electrode by protecting tissue from mechanical and thermal damage.