Feasibility of the set-up for the different approaches in robotic head and neck surgery with the Versius Surgical System

The Versius Surgical System is a next generation soft-tissue robot with instrument and endoscope arms split into individual modules. Despite its similarities with previous systems, the basic changes in the design raise concerns relating to the feasibility of the set-up for the different approaches in robotic head and neck surgery procedures. We used a complete unit with a surgeon’s console and four modules on a training mannequin to depict the different configurations in the operating room. We tested transoral robotic surgery and the four basic configurations for the remote access to the neck: transoral/transvestibular, retroauricular, axillary and bilateral axillo-breast approaches. We obtained a high quality simulation for transoral robotic surgery, as well as for the usual remote access approaches, except for the axillary approach. We were able to obtain an optimal distribution of the modules around the surgical table and an adequate configuration of the joints allowing the instruments to reach their targets. The Versius Surgical System might be an alternative device for robotic procedures in head and neck surgery, although this needs to be proved in a clinical setting.


Introduction
Next generation soft-tissue robotic surgical systems are already in the market [1].Although there is more than 20 years of clinical experience and the general design for telemanipulation appears quite similar [2], the feasibility of the different applications for each device still needs to be proved [3].Unlike the previous systems, the Versius Surgical System (Cambridge Medical Robotics, UK) uses similar wristed instruments but the instrument arms are split into individual modules.The dimensions and specific configuration of the joints in the arm modules are designed to reproduce conventional laparoscopic surgery.
Therefore, the basic concern for head and neck surgeons is whether the current approaches for head and neck robotic surgery are reproducible with the new device.With slight variations, four basic approaches are currently used [4].An approach that is superior and medial, including both conventional transoral robotic surgery (TORS) and transoral-transvestibular approach to the neck, a superior and lateral, the retroauricular approach, an inferior and lateral, the axillary approach, and an inferior and medial, the bilateral axillobreast approach (BABA).
We set to demonstrate the physical feasibility of distributing the different elements of the Versius Surgical System in the operating room (OR) so that the instruments reach their targets and allow for an accurate vision and instrumentation for each approach in robotic head and neck surgery.

Materials and methods
We had a physical unit available of the Versius Surgical System with a surgeon's console, an endoscope arm module and three instrument arm modules to assemble the basic set-up for the different approaches in robotic head and neck surgery.To simulate an OR environment we used a standard surgical table and a training mannequin (MegaCode Kelly, Laerdal, Norway).
For TORS simulation we used the FKWO pharyngolaryngoscope (Olympus, Japan) as mouthgag.As the mannequin is used for orotracheal intubation training, high quality simulation was expected.Remote access approaches to the neck were simulated over the skin.The target for TORS was the larynx, and for remote access approaches the thyroid gland (other possible targets are closer).
The modules (both instrument and endoscope modules) have a side square footprint of 38 cm.The base of the first joint is roughly at the level of a standard table (80 cm) although its height is adjustable (it can be raised 45 cm).The robotic arm has three joints (shoulder, elbow and wrist) to allow for an adequate positioning.Instruments are 6.8 mm in diameter with a stem 32 cm long.The endoscopes (0° and 30°) are 10 mm in diameter.Image acquisition in analogic with a double endoscope: panoview 3D HD (Wolf, Germany).The endoscope arm holds a double (3D) camera head.
We also had an assistant surgeon, and room for the scrub nurse, instrument tables and anesthetic equipment was estimated.

Results
With the mannequin laying supine in the operating table, the FKWO was positioned and the upper airway exposed.The system was set for a standard TORS approach with three robotic arms: endoscope in the midline and two instruments at both sides.The endoscope arm module and one instrument arm module were situated at one side, and a second instrument arm module on the other side, with the assistant surgeon at the head of the table.The three joints of each arm were arranged in a continuous arch following a C configuration.The set of the virtual pivot point is a manual maneuver and setting and modifying it, which is usual in a TORS procedure, took some time.However, the set-up was feasible and at the console it appeared as a standard TORS (Fig. 1).The transoral-transvestibular approach in also a superiormedial approach and depicts a similar configuration with endoscope and two instruments.
The retroauricular approach is superior and lateral, also with the endoscope and two instruments.A similar configuration was used, with a rotation of the elements to the chosen side for the approach.
The axillary approach is an inferior and lateral approach that can use three or four arms.It is difficult to accommodate three modules, let alone leave working space, as the modules cannot be positioned on the opposite side of the table for the arms will not reach the entry site.
Finally, the BABA, which is inferior and medial, was easy to depict as arm modules are positioned quite apart from each other.The joints were set in a Z configuration (the third joint in an inverse arch related to the second joint), which is an optimal working configuration.
The neutral position of the first joint in the arm modules is vertical upwards.The second joint must be necessarily arched towards the table.As the first two segments of the arm are roughly 40 cm long, for every set-up the modules have to be fairly close to the surgical table for the segments of the arms to be at convenient angles: not too closed but also not too flat.If two segments become aligned it would cause what in robotics or kinematics is called a singularity and the robot will stop moving or move in an unexpected manner (which actually happened several times during the trial).

Discussion
Except for the axillary approach, which either way is being abandoned, the set-up for the different approaches for robotic head and neck surgery is feasible and comfortable with the Versius Surgical System.This was the expected outcome, as except for the retroauricular approach that was originally described as robotic [5], transoral surgery and the other remote access approaches to the neck were historically started as endoscopic procedures [6][7][8].
Versius does not require the use of cannulas at the distal end of the instrument.Of course they must be used for percutaneous approaches, but not for TORS or the retroauricular approach.Consequently, there is more space at the entrance of the surgical field which facilitates the assistant´s work.However, we do not know how stable the distal end of the instrument will be without the distal support in a clinical setting.Compared to the most widely used device, although the endoscope is wider (10 mm), the instruments are narrower (6.8 mm).
Other items that need to be accommodated around the surgical table are the anesthetic cart, which should be connected to the patient by the endotracheal tube, as well as monitoring and vascular access systems; for safety reasons, the possibility of a quick access by the anesthesiologist should be warranted [9].The design of the manual dismantling of the Versius Surgical System allows for this.
The scrub nurse and instrument tables need to be inside the scrub area, although additional instrument requirements should be limited.The availability of robotic instruments is still a limiting factor for some procedures, as advanced energies (harmonic and advanced bipolar seal and cut) are not available yet for this system.A problem can also be raised with the length of the instruments for the remote access in some patients.
In summary, the Versius Surgical System might be an alternative device for robotic procedures in head and neck surgery, although this needs to be proved first in and experimental environment and then in a clinical setting.

Fig. 1
Fig.1Set-up for transoral robotic surgery with the Versius Surgical System.Left.Surgeon at the console.Notice at the monitor the simulated surgical field view (oropharynx and larynx) with the 30° endoscope.Polarized glasses are required for the 3D view.Center.Assistant surgeon at the head of the surgical table.Notice the position of