Discussion
Transoral approach can be considered a simple and successful procedure to treat large (>7 mm) and deeply located stones (proximal duct and hilo-parenchymal area) of submandibular gland.5,6
Recently, transoral robotic surgery (TORS) has become a valuable approach in head and neck cancer surgery, and it has been progressively adopted also for anterior oral floor diseases.7Initial experiences of transoral robot-assisted treatment of submandibular sialoliths have been performed with the Da Vinci robotic system.8 Its limitations are the rigid and relatively bulky robotic arms, a limited number of cutting devices available, and high costs.8 In the last years, the Flex Robotic System has been specifically developed for head and neck surgery.7 It is as safe and effective in transoral robotic surgery for lesions in the oropharynx, hypopharynx, or supraglottic larynx.7 Despite the increasing literature showing successful results with the Flex Robotic system for head and neck tumours, it has never been applied to the anterior oral floor.
The aim of this paper was to describe the transoral robotic approach with the Flex Robotic system for the removal of a giant (25x15 mm) and deep hyloparenchimal submandibular stone. No problems were found during docking, that appears comfortable and easy to set with Flex retractor. This system, being easier to handle than the Da Vinci system, allowed a fast and simple setup. The stone was successfully removed en bloc, without per-operative complications. The total procedure time was about 30 minutes, thus minimizing tissue damage in the oral floor and subjective complaints. A minimally invasive approach with a smaller incision of the oral mucosa was done and this was favored by the size of the stone that made it clearly palpable; usually, in loupe lens guided transoral surgery the extent of the oral mucosa incision is wider and this approach permits an adequate and safe check of anatomical landmarks bringing to hyloparenchymal area. Maryland dissector guaranteed blunt dissection of proximal third of the Wharton’s duct till the parenchyma to follow the stone in a clean surgical field, favoring a better view of the deep surgical plane. No post-operative complications were observed.
According to our experience the main errors to avoid are:
The 3D view of the surgical field, guaranteed by the Flex Robotic system, improves the visualization allowing the surgeons to have a clearer anatomical delineation and enhances depth perception of oral floor. Furthermore, the shared 3D-HD monitor allows the second surgeon to have the same view of the first surgeon that is promptly helped through suction, tissue traction, and push-up of the gland from the neck.
Unlike Da Vinci instruments, which are rigid, bulky, and controlled by a remote robotic system, the Flex Robotic instruments, easier to handle, are controlled behind the patient by the surgeon’s hands, ensuring haptic feedback and tactile sensation, allowing to control the force applied to the tissue.6 Different instruments are available, whose flexibility combined with flexible robotic scope ensure an optimal visualization and maneuverability in a small and deep surgical field.
In conclusion, surgical transoral removal of large (>7 mm) and deep submandibular stones with the Flex Robotic system appears to be a minimally invasive, safe and effective conservative procedure with maximal functional and aesthetic outcome. Furthermore, the preservation of the Wharton duct allows sialendoscopic access in case of residual microliths, or to perform a new conservative transoral approach in case of stone recurrence.