Introduction: Bipolar vessel-sealing devices (VSDs) have advantages in urological surgeries (less hemorrhage, shorter operating time). However, these instruments can cause thermal injuries, which can result in neural damage and necrosis. The objectives of this study were to establish a reproducible in vitro model for standardized assessment of electrosurgical devices and to evaluate whether optimized placement of surgical instruments can reduce the thermal spread. Methods: We evaluated thermal spread of two VSDs in vitro using thin bovine muscle strips. Thermal injury was measured using an infrared camera, temperature probes and histology. The recordings were made with the VSD alone and with a rectangular clamp next to the VSD. Results: Both instruments showed a significant temperature spread of 2.5 mm lateral to the VSD. The placement of a metal clamp next to the VSD significantly reduced the temperature spread. Histological examinations were able to underline these findings. Conclusions: In this study we describe a straightforward clinically relevant in vitro model for the evaluation of future electrosurgical instruments. We demonstrated that the thermal spread of VSD could be further reduced by optimized placement of an additional surgical instrument. Our results could help surgeons protect sensitive structures like nerves in the vicinity of the VSD.