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:
- to perform the procedure without a correct position of the Flex
retractor and an appropriate exposure of the oral floor, this may lead
to an inadequate surgical field;
- to perform the procedure without external pressure over submandibular
gland, this may make the stone identification difficult and increase
the risk of injuries to Wharton’s duct and lingual nerve;
- to make an excessive use of the monopolar cautery, this may favor the
heat transmission to the lingual nerve with consequent injury;
- to perform a wide incision of the duct, not only over the stone, this
may increase the risk of post-operative ductal stenosis.
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.