A surgical and anatomo-histological study on Transoral Endoscopic Thyroidectomy Vestibular Approach (TOETVA).

Background: The number of TOETVA surgeries has increased worldwide but the anatomical passage of trocars is not clearly defined. We aimed to define detailed surgical anatomical passage of the trocars in cadavers. The incisions in oral vestibule, anatomical pathways of trocars, affected mimetic muscles, neurovascular relations of trocars and histological correlation of surgical anatomy were investigated.
Methods: Four cadavers and 6 six patient oral vestibules were used. The locations of optimised vestibular incisions were measured photogrammetrically. Initial steps of TOETVA surgery were performed on cadavers according to those optimal incisions. TOETVA preformed cadavers dissected to determine anatomical passages of the trocars. Afterwards, flap of lower lip and chin were zoned by software appropriate to the trocars routes. Histological analyses of the zones were made in correlation with dissections.
Results: Mimetic muscles associated with median (MT) and lateral trocars (LT) are orbicularis oris, mentalis, depressor anguli oris, depressor labii inferioris and platysma muscles. Trocars affect mimetic muscles in the perioral, chin and submental regions in different ways. The risk of mental nerve injury by MT is low. LT pass through the DLI muscle. The transmission of LT to the subplatysmal plane in the submental regions can be in two different ways. The arterial injury risk is higher with LT than the MT.
Conclusions: The surgical anatomy of the perioral, chin and submental regions for the initial TOETVA steps has been defined. Detailed surgical anatomical passages of the MT and LT were determined. Anatomical pattern to reach subplatysmal plane are presented. Mimetic muscles effected by trocars were determined. Endocrine surgeons should know the anatomical passage of TOETVA trocars.