Robotic microlaryngeal surgery: a new retractor that provides improved access to the glottis

Few in vivo studies have been reported to investigate the efficacy of RMLS. Two studies
used the Dingman mouthgag and a 30° scope to attain a working view of the larynx in
a mannequin and cadaver, respectively (Hockstein et al. 2005a], b]). Lalich et al. invented a retractor and conducted a study in cadavers with adequate
access reported, but the retractor has not been trialed in an in vivo human model
to date (Lalich et al. 2014]). One study required the use of anterior tongue retraction with a 2.0 silk suture,
malleable blade to retract the tongue base, and a Lindholm scope to retract the epiglottis.
The robotic arms were inserted on either side of the Lindholm scope (Blanco et al.
2011]). Resection of T1 glottic cancers have been successful in a small number of studies,
but inadequate exposure was a recurrent theme (Park et al. 2009]; Byrd and Duvvari 2013]; Kayhan et al. 2012]; Lallemant et al. 2013]). An FK retractor was used in two studies, but the cumbersome nature of the retractor
resulted in collision with the robotic arms and limited access to the anterior commissure
in both studies. (Dogan et al. 2001]; Blanco et al. 2011]).

The senior author has used the Dingman, Crow Davis and FK retractor in the past and
developed the MOR system as a simpler option with a wider range of applications. These
previously described retractors are ideal to address the oropharynx particularly the
palatine tonsil region but are limited in their exposure to other regions of the pharynx
or larynx. The FK retractor is especially cumbersome in its use and its exposure of
the larynx is very limited, especially in visualization of the anterior glottis. The
MOR system was developed with two pivot points on the brace and a wide range of blade
designs and can replicate the function of a Dingman or Crow Davis retractor. These
features allow the user multiple set up options depending on the anatomical area being
addressed. Our institution has not required use of the FK or any other retractor since
the MOR became available. Unfortunately, direct comparisons between several retractors
in a patient have not been performed due to the risk of unnecessary patient injury
from insertion to removal of the retractor and significant operative time delay including
use of the robot. A cadaver study in the future may have merit in this regard.

Our method showed successful robotic-assisted resection of glottic tissue using the
MOR system. The MOR system eliminated the need for a rigid circular laryngoscope,
which narrows the visual field, increases the distance of the working view to the
surgical site and serves as an obstacle around which the robotic arms have to work.
The MOR system did not require a stay suture to retract the tongue. Suturing the tongue
can cause tongue edema, resulting in limited access and visualization of the surgical
site as well as patient discomfort. The retractor has an axis of rotation at the base
of the blade that optimizes elevation of the tongue and allows for retraction of the
tongue down to the vallecula (Fig. 5). The MOR system includes 24 different blades each of which are customized to overcome
commonly encountered anatomical challenges including a large tongue, large base of
tongue, or an epiglottis that obscures view of the anterior glottis. The 360° axis
of rotation at the pivot of the base of the blade and the inferior portion of the
mouth retractor allows excellent exposure of the entire glottis which will likely
eliminate the need for a tongue suture in most patients. The curvature of some of
the available blades also serves to push the base of tongue anteriorly and allow adequate
visualization of the glottis. The maxillary brace also has a 360° axis of rotation
that further augments the ability of the retractor to push the tongue and epiglottis
forward, allowing visualization of the glottis (Fig. 6). The ability to rotate multiple parts of the retractor around an axis in order to
maximize exposure is not possible with other retractors that have been proposed for
use in robotic surgery. The robot eliminated tremor as a cause of potential human
error and allowed for 360° access to the lesions, which in our case was redundant
supraglottic tissue that had prolapsed into the glottic airway.

Fig. 5. The MOR system displaced with one of the multiple tongue blade options that can be
exchanged depending on each patient’s anatomy

Fig. 6. Both the maxillary brace and pivot at the base of the blade have a 360° axis of rotation
which improves exposure of the glottis

Disadvantages of RMLS include limited instrumentation in which success varies depending
on each patient’s anatomy, limited tactile feedback requiring the surgeon to rely
on visual cues, and limited robotic training programs. Oncologic outcomes using RMLS
have not yet been studied or compared to traditional surgery (Byrd and Duvvari 2013]). Limitations of this study include that the MOR system has only been evaluated in
one case thus far, which limits its generalizability. It has not yet been tested across
a wide variety of patient with different anatomy and body habitus. The blade on the
retractor does not retract the epiglottis, which is sometimes necessary for exposure
depending on the patient’s anatomy. When using the MOR system, attention needs to
be given to the size and width of the tongue blade so that the base of the vallecula
is reached for optimal glottic exposure. In some cases, the epiglottis may need to
be retracted for exposure. We have created multiple blade sizes to address this issue,
including a blade similar to the superior aspect of a Lindholm blade that can connect
with the MOR brace (Fig. 7). This modification of the Lindholm blade that is commonly used in microlaryngeal
surgery gives the robotic surgeon similar access to the larynx. With the recent release
of the new da Vinci Xi surgical robot, we believe the MOR system will be even simpler
to use with wider application, as the robotic arm instruments are 5 cm longer and
more slender.

Fig. 7. A blade option similar to the superior aspect of a Lindholm blade