Safe distance between electrotome and recurrent laryngeal nerve: an experimental canine model

Various energy based surgical devices (ESD) like electrotome have been widely applied in thyroid surgery. This is the first canine model to determine the safety margin of using the electrotome near the recurrent laryngeal nerve (RLN) to prevent injury to this nerve during thyroid surgery.

Eighteen healthy male dogs were divided equally into three groups according to the distance between electrotome application and the RLN: Group A (5 mm), Group B (3 mm), Group C (1 mm). The parameters of evoked electromyography (EEMG) of vocal muscles between right normal RLNs and left RLNs after electrotome application at a power of 30 W for 1 second in each group were recorded and compared. The acute microstructural morphological changes of the RLNs were observed immediately after the operation under electron microscope.

In Group B and Group C, after using the electrotome at a vertical distance of 3 mm or 1 mm from the left RLNs, the stimulating thresholds of left RLNs had a significant increase (P = 0.005; P = 0.002) compared with right normal RLNs, and there occurred obvious acute microstructural morphological changes under electron microscope for left RLNs. While there was no significant functional or histological changes for left RLNs after using the electrotome at a vertical distance of 5 mm from the RLN (P = 0.187) in Group A.

When using the electrotome near the RLN at a power of 30W in thyroid surgery, a safety margin of more than 3 mm should be recommended.