Acute Effects of Ultrasonic Shears and Monopolar Electrosurgery on Sciatic Nerve Electrophysiology

Background: When using energized surgical devices in the vicinity of nerves, care must be taken to reduce the risk of thermal or electrical injury. For example, during thyroidectomy, it is critical to avoid damage to the recurrent laryngeal nerve while dissecting and coagulating nearby tissue.

Methods: We compared use of Harmonic ACE+ and Focus ultrasonic shears and monopolar electrosurgery to scissors as a control applied to make incisions in muscle 2 mm from the sciatic nerve in rats. Via electrophysiological monitoring, the compound action potential and conduction velocity were determined over a three hour post-application period. Neuromuscular response was observed by von Frey hair stimulation. Leukocyte infiltration was measured via H&E staining, and impaired axonal transport via β-APP immunohistology.

Results: None of the energized devices had a significantly different compound action potential than scissors, although electrosurgery exhibited prolonged depolarization and repolarization times. Electrosurgery had significantly slower conduction velocity and increased von Frey stimulation force compared to scissors, whereas both ultrasonic devices were not different from the control. No difference was observed between devices for leukocyte infiltration, but electrosurgery had significantly greater β-APP levels than scissors, while again ultrasonic devices were not different.

Conclusion: Electrosurgery caused significantly more neurophysiological damage than scissors. In contrast, the ultrasonic shears were not statistically different than scissors in terms of nerve injury. Harmonic ACE+ and Focus can be used to cut and coagulate tissue near nerves with a low risk of electrophysiological injury.