You need to get a mouth-gag to start TORS. How to choose?

You definitely cannot perform TransOral Robotic Surgery (TORS) without a mouth-gag. Unlike in percutaneous robotic surgery where cannulas go through the skin and the surgical field is maintained by the insuflation of CO₂, in TORS you need a device that keeps the mouth opened and, most important, that retracts the tissues (particularly the tongue) so that the target anatomy is exposed to the robotic instruments introduced through the mouth.

But this is not new. We are used to such devices in conventional transoral surgery. Either for surgical procedures in the oral cavity, the oropharynx or the larynx/hypopharynx there are many different purpose-designed tools. We usually apply frame-type tools for the proximal anatomy (ie. to work in the oral cavity or to perform a tonsillectomy) and tubular-type tools to work on distal targets (like the larynx). There are a multitude among which to choose. What´s the problem?

Back to the origins

Back in 2004, when Greg Weinstein and Bert O´Malley at Upenn were figuring out how to use the original da Vinci standard through the mouth, the target anatomy was the larynx. They were trying to find a surgical alternative to Transoral Laser Microsurgery (TLM) which, besides some technical limitations, had an important learning curve and reproducibility issues.

They inmediately realized that they would not be able to introduce the robotic instruments through the conventional tubular devices (laryngoscopes, pharyngoscopes). Those were designed to be used for conventional laryngeal microsurgery or TLM where a narrow working corridor was enough. But the design of the robotic arms requires a triangular configuration to reach the target (figure 1), where the base has a minimum width so that the instruments and the endoscope do not collide.

The solution was obviously a frame-type device, with a frame wide enough to accommodate the robotic arms. Several existed already. Among those with a “panoramic” design we do have the Jennings mouthgag and the Dingman mouthgag. The Jennins will not hold the tongue, so it is not useful for this purpose. The Dingman is ok, and it also has a set of interchangeable blades. There are other similar devices like ones conventionally used for plain tonsillectomies (Crow-Davies and the like). But all of them are designed for surgical procedures on the orophaynx. They might be useful in certain TORS procedures (ie. lingual tonsillectomy for sleep apnea) but in most cases, it is impossible to obtain an appropriate exposure for oncologic surgery on the distal oropahrynx (be it the base of the tongue or the inferior part of the lateral wall) and the larynx.

But people from Upenn were lucky, and found the best possible candidate. They remembered the FK. Many years ago, two german otolaryngologists had designed a “laryngopharyngoscope”. The FK (Feyh-Kastenbauer) was and hybrid design that combined a frame like those on the conventional mouthgags which also sat on the upper jaw, and interchangeable blades. The difference was that the blades were to play the part of the previous laryngoscopes and they were not only interchangeable but also adjustable in length. The device was made to widen the surgical field for TLM, but surgeons preferred to keep on using the tubular devices so the FK was only marginally used.

Nevertheless, it was possible to perform TORS using the FK and it became one of the cornerstones of the original design of the technique.

Designing the FKWO

This is really the story of a renaissance (figure 2).

Weinstein and O´Malley used the FK to do the pre-clinic investigation for TORS and started surgery in the clinical setting with it. But they also re-designed the device to meet their own ends.

They made two basic modifications. They widened the frame so it was more proportionate to the dimensions of the opened mouth and there was more lateral space to accommodate the vastagus of the endowrist instruments.

But the second modification was more relevant. They designed a new set of blades, specifically for TORS. The new blades were aimed to expose the supraglottic larynx and were inspired on the Lindholm laryngoscope². The configuration of the blade represents the upper portion of the laryngoscope, which actually retracts the tongue. The distal end has a lineal design to sit on the vallecula, right on the transition between the base of the tongue and the valleculla proper. They are built right and left, with a small wing to help hold the tongue laterally. They are also built long and short to accommodate different anatomies (the short blade is also helpful when the base of the tongue needs to be exposed). So there are four new blades adding to the original ones in the FK (figure 3).

Thereby the Feyh-Kastenbauer-Weinstein-O´Malley was launched. Originally built by Gyrus, the device is now owned by Olympus.

Issues with the FKWO

There are several other features in the new FKWO.

It comes with a fiberoptic light to aid in the positioning of the device. However, it is held with a clip to the blade which is quite unstable. We prefer to use a conventional head-light.

It is also possible to attach some other items to the frame. There is a set of retractors of the commissure of the mouth (obviously copied from the design of the Dingman). But they do not help and usually disturb; so we never use them. Also, it is possible to attach a cannula for aspiration. Again, you never get the aspiration where you need it, so it is not a substitute for the hand-held aspirator of the assistant.

One real improvement is the articulated arm to hold the FKWO at the end of its vastagus. Since it is attached to the surgical table it is really stable and much better than the conventional pectoral support used conventionally for endolaryngeal surgery. Remember that when Weinstein and O´Malley first described TORS they recommended that the FKWO should be stabilized at two different sites as there was a real risk that it would be displaced during surgery by the arms of the da Vinci. This is no longer necessary with the articulated arm.

However, the FKWO is not a friendly device. It is tricky to manipulate and quite aggressive for the patient. It needs to be positioned with extreme care to minimize the risk of hurting the patient (on the tongue, lips, tonsillar pillars…). You better hold it like a laryngoscope for positioning (video 1). Turning the wheels is a little nightmare. Nevertheless, you need the FKWO to perform TORS. Our feeling is that it is the least bad option.

Are there alternative devices?

There are some alternative “phayngolaryngoscopes” in the market.

In year 2011 Mark Remacle and Georges Lawson published the first clinical experience with the device they had designed, the LARS: Layngeal Advanced Retractor System (figure 4).

The design is obviously based on the FKWO. They further widened the frame to a real “landscape” type, which is in our view its only contribution.

We had the opportunity to use it in surgery and found two main drawbacks. The first one is that they did reproduce the blades of the original FK, but failed to offer something like the TORS blades of the FKWO. This are the blades we use for almost every case.

The second one is the attachment of the blades to the frame. In the FKWO the blade is a “step down” from the gearwheel. The LARS lacks this distance, so the frame blocks part of the surgical corridor.

Some of our colleagues in other countries in Europe are using the Moriniere retractor built by Microfrance (figure 5). Again, we had de opportunity to test it in a clinical setting. It has the theoretical advantage of the possible angulation in the horizontal plane (video 2). We found no use for that. But cogwheels have a better design and are more friendly.

Also, similar problems with the blades (too straight and too high on the frame).

We also had the opportunity to test the Flex retractor (figure 6). As far as we know, there is none in this country. People from Medrobotics were kind to lend us one unit for one of our courses.

The Flex retractor was designed to be used with the Medrobotics Flex Robotic System. The frame is curved on the sides, but it lacks the notch midline down (it helps the frame of FKWO to somehow get out of the way). Also, the levers are friendly and again it has an original movement of blades, which is oscillation on the sagittal plane (again we found no use for that).

The blades are quite curved with a suction cannula incorporated and come in a number of sizes and shapes to accommodate to different anatomies. However, they are designed to retract the tongue but not to expose it. Also, it is important to remember that this mouthgag is designed for a flexible robot so the blades are not optimal for the rigid endowrist of the da Vinci.

Finally, a show-stopper, it is stabilized with a hook (like conventional mouthgags) so it is quite difficult to set it in a stable position for TORS.

There are some other “exotic” designs, like Satou´s curved laryngoscope³ but, as far as we know no other versatile and adaptable devices like the ones described above.

The best is yet to come

The conclusion is that we need a better pharyngolaryngoscope. Many colleagues are working on it, but it is not here yet.

We hope this information is useful. Meanwhile, in case you need some advice or want to learn more about our experience, please contact us.

Jose Granell, September 2021

(no royalties from any of the companies)

¹ Remacle M, Matar N, Lawson G, Bachy V. Laryngeal advanced retractor system: a new retractor for transoral robotic surgery. Otolaryngol Head Neck Surg. 2011 Oct;145(4):694-6. doi: 10.1177/0194599811415930. Epub 2011 Jul 15. PMID: 21765059.

² Benjamin B, Lindholm CE. Systematic direct laryngoscopy: the Lindholm laryngoscopes. Ann Otol Rhinol Laryngol. 2003 Sep;112(9 Pt 1):787-97. doi: 10.1177/000348940311200908. PMID: 14535563.

³ Eguchi K, Chan JYK, Tateya I, Shimizu A, Holsinger FC, Sugimoto T. Curved Laryngopharyngoscope With Flexible Next-Generation Robotic Surgical System for Transoral Hypopharyngeal Surgery: A Preclinical Evaluation. Ann Otol Rhinol Laryngol. 2019 Nov;128(11):1023-1029. doi: 10.1177/0003489419856391. Epub 2019 Jun 20. PMID: 31220916