Comparing the safety of harmonic ACE and ACE+ around the recurrent laryngeal nerve in swine models

Purpose: Among the various energy-based devices, ultrasonic shears are popular in thyroid surgeries. In this study, we tested the safety of Harmonic ACE and Harmonic ACE+ around the recurrent laryngeal nerve (RLN) in experimental swine models. Methods: Harmonic ACE and Harmonic ACE+ were each tested in 4 piglets. Harmonic ACE and Harmonic ACE+ were activated at a 0- to 5-mm distance from the RLN. The function of the RLN was assessed using continuous electrophysiological monitoring. Results: For Harmonic ACE, there was no adverse EMG event found when activated at 4- and 5-mm distances from the RLN. At a 2- to 3-mm distance, there were 4 adverse EMG events observed. In these 4 cases, adjacent tissue shrinkage occurred after 6 to 15 seconds of activation, and the RLN touched the Harmonic ACE. At a 1-mm distance, there were 2 adverse EMG events found after 25 seconds of activation. For Harmonic ACE+, there was no adverse EMG event observed when activated at 1- and 3-mm distances from the RLN. At a 0-mm distance, 2 adverse EMG events occurred after 6 to 10 seconds of activation. Conclusion: The safe distance of Harmonic ACE and ACE+ was 4 and 1 mm, respectively, in the swine models. Harmonic ACE+ is safer than Harmonic ACE because it did not cause any tissue shrinkage. Surgeons need to understand the characteristics of devices for safe operation.