Consequences of Trocar Dynamics on Mental Nerve in Transoral Thyroidectomy.

Zhang, Daqi; Li, Shijie; Dionigi, Gianlorenzo; Wang, Tie; Zhang, Jiao; Xue, Gaofeng; Sun, Hui

BACKGROUND Mental nerve (MN) injuries are reported during transoral endoscopic thyroidectomy vestibular approach. Effect of trocar insertion and position on MN are examined in the present study. MATERIALS AND METHODS Ten millimeter incision was made at the center of the lower lip oral vestibule. Two 5 mm lateral incisions of the lower lip oral vestibule were made at the junction between the incisor and the canine. These 2 lateral incisions were high, just below the edge of lower lip. Nine pigs (18 MN) were randomly divided into 3 groups and MN dissection was performed. The angle between the lateral ports and median line were changed between 15 and 45 degrees among 3 groups and effect on MN was examined. RESULTS During dissection when insertion and other ports are in neutral position visual inspection of MNs did not reveal any compression bilaterally. The distance between MN and the ports was 18.2±2.1 mm (16.3 to 21.2 mm). In group I and group II, MNs have no compression by the lateral trocars. In group III (45 degrees), left MNs were all compressed. Two MNs (66.7%) were compressed on the right side. The MN was compressed at its ramification. CONCLUSIONS The results of the present experimental study, endorse the suggested medial and lateral vestibular incisions for transoral endoscopic thyroidectomy vestibular approach. However, during dynamic modification of the lateral port position/angle, MN compression was observed when the angle was >45 degrees.