Different approaches of robotic-assisted remote-access thyroidectomy with multiport da Vinci systems have been developed in the past 14 years since Chung performed the first such transaxillary (TA) approach in October 2007 (1). In addition to the transaxillary route, surgeons have applied the bilateral axillobreast (BABA) (2, 3), retroauricular or facelift (FL) (4, 5), and transoral (TORT) (6, 7) approaches safely in patients. Nevertheless, the method that produces the best clinical outcomes is not yet certain, as each robotic-assisted thyroidectomy approach has its advantages and disadvantages. There are still concerns regarding various aspects of the procedure such as the operative invasiveness to create the subcutaneous flaps accessing the gland, gasless versus gas, difficulty to reach the contralateral side for bilateral dissections, distance from skin incision to the gland, location and cosmesis of the skin incision, surgical view onto the anatomy, ability to use all robotic arms, need for retractors, nerve injuries, infections, and control of hemorrhage, among others (8). We applied a presternal approach to assess whether any of these aspects could be overcome with the next-generation single-port da Vinci SP system. The da Vinci SP system is a progression from the da Vinci multiport systems whereby three instruments and a stereoscopic camera are employed through a single port on a single instrument arm (Entry Guide Manipulator, EGM). This EGM is docked to the SP cannula of 28 mm outer diameter placed in the body wall. Elbow joints proximal to the wrist on the instruments, camera triangulation, and independent planar movements of the instrument tips allow access to narrow workspaces and avoid external collisions. Initial clinical cases with the da Vinci SP system in thyroidectomy were limited to the transaxillary approach but have shown excellent cosmetic outcomes and reduced postoperative pain due to a smaller skin incision and the reduced extent of flap dissection (9). The aim of this study was to evaluate the feasibility of a remote-access thyroidectomy through presternal and submental approaches with the da Vinci SP system and allow for a basic initial comparison to the other robotic thyroidectomy approaches.

The procedures were performed in five human cadavers in a surgical lab certified for research and development (DIN EN ISO 9001:2015) and carried out in accordance with ethical standards and the declaration of Helsinki 1964 and its subsequent updates. Further, it did not require approval from the institutional review board as living humans were not included. Table 1 lists the characteristics of the cadaveric models used and the approach applied.

Performing remote-access thyroidectomy through either a presternal or submental approach with the da Vinci SP system was feasible in our cadaver study. We believe that these approaches might address some of the concerns of robotic remote-access thyroidectomy and have some particular advantages in consideration to other robotic thyroidectomy methods. No additional ports or retractor devices were required to expose the gland and complete the bilateral resection. The ability of the SP system to work in a small narrow space decreases the amount of skin flap that needs to be dissected for access to the gland. Specifically, in the presternal approach, there is a limited risk of tissue damage during the creation of the presternal flap as the posterior surface is a bone and no nerves or breast tissue lie subcutaneously in this empty space. Dissecting the presternal tunnel or submental flap required only a small skin area and compares well with the mean area of dissection required for FL and is better than for TA, which Singer et al. (10) reported in their morphometric analysis. The distance from the incision site to the thyroid gland, with an average of 15 cm in all cadavers, is like BABA, TA, and FL and shorter than what was reported in TORT (19 cm) (11). Since only a single arm needs to be docked with the SP system, complexity is reduced and the setup was very quick, shortening the procedure time. Comparing our combined skin flap development and docking times from these initial labs with docking times to earlier patient series in other robotic approaches shows a noteworthy reduction in the required time. It took us between 5 and 8 min in the models, which is much shorter than what has been reported in multiport approaches for TA (28 min) (1), FL (68 min) (12), and BABA (61.8 min) (2) and is also shorter than the 38 min reported by Kim et al. (9) for the SP system in their series. However, our procedures were performed on deceased patients, and we did not have to deal with hemostasis and other surgical matters that would apply to a live patient. Yet, we believe that for a trained surgical team in a clinical case, it would be possible to get close to these times after some experience. Due to the midline exposure similar to open surgery and familiar to thyroid surgeons, a wide surgical view of the gland in a natural position is enabled. This allows for total thyroidectomy approaching both lobes. The parallel configuration of the instruments through the SP cannula enables using all three SP instruments simultaneously for exposure with full dexterity. Also, since the patient is placed supine and the neck stays straight throughout the surgery, there would be no movement or shifting of the intraoperative nerve monitoring (IONM) tube, and the risk of brachial plexus injury due to arm positioning would be eliminated.

Potential disadvantages of our method might be the possibility of hypertrophic scarring at the incision site for the presternal approach. In the submental approach, the scar can be hidden cosmetically, like with a facelift procedure. As we performed the procedures under CO₂ insufflation, any complications related to it (subcutaneous emphysema, embolism, etc.) would apply in clinical cases. Another concern is the unavailability of an ultrasonic dissector adapted for the SP system like the Harmonic ACE (Johnson & Johnson Medical Inc., New Brunswick, NJ, United States), which is the preferred dissection instrument by many robotic thyroid surgeons. However, in their initial SP thyroidectomy series of 10 patients, Kim et al. (9) became comfortable after the third case with the mono- and bipolar SP instrumentation energized by the integrated electrosurgical unit and found it a safe and effective alternative to the harmonic scalpel.

Our feasibility study has several shortcomings because it was performed in cadavers. First, any postoperative outcomes such as pain, voice impairment, swallowing, complication rates, or the impact of ventilation and bleeding from structures in a living human were not possible. A major concern remains satisfactory postoperative cosmesis with the presternal approach and the incision placed right between inframammary folds. While the incision might be hidden in a woman at the position where the bridge between the left and right cup of a bra would sit, it would be visible on the bare chest in a male. The question remains if this is an acceptable result. Cao et al. (13) performed endoscopic thyroidectomy with a 15-mm port placed in the same presternal location as in our study, and of 282 patients, 78.7% rated the cosmetic result as extremely satisfactory and an additional 13.9% rated as good, despite the presternal 15-mm incision. Nevertheless, the cosmetic benefit is something to be evaluated. In the submental approach, the interference with the wound retractor was an issue in the first cadaver but was resolved by moving the incision slightly inferior and keeping some slack in the sleeve of the access port in the subsequent cases. Nevertheless, in cadaver 4, the longer sleeve was punctured by the monopolar scissors during an instrument change, leading to some loss in CO₂ insufflation. Care must be taken at the access port interface during these maneuvers to avoid any issues. Hence, unless these approaches are investigated in clinical cases, we will not be able to answer whether they will provide any significant patient benefit in the postoperative outcome, including a reduction in cost due to shorter operating room (OR) time while at the same time not ignoring oncologic outcome with these new surgical techniques. This also applies to a comparison with laparoscopic surgery. Our experimental cadaveric setup was not designed to determine whether a meaningful outcome improvement is achievable compared to laparoscopy. We can only imagine that a submental or presternal approach with laparoscopic instrumentation would be challenging to execute. Our study did not assess specific challenges that surgeons with limited experience with the da Vinci SP system might encounter in performing the described techniques. Lee et al. (14) compared two patient cohorts in retroperitoneal adrenalectomy treated with either the da Vinci SP or a da Vinci Si/Xi (multiport) system. All surgeries were done by the same surgeon (SWK, co-author of this report) with more than 10 years of experience with the multiport da Vinci systems. They found no difference in the mean operation time on these first da Vinci SP cases compared to the da Vinci Si/Xi cases from their previous experience. The team was able to reduce the OR time reasonably in the starting stage and concluded that the operation times with da Vinci SP would likely be shorter as future experiences are accumulated and that SP facilitated easier and more convenient operations for surgeons. Therefore, we believe that the SP learning curve is relatively short and not an obstacle for experienced robotic surgeons.

This study demonstrates the feasibility of a bilateral thyroidectomy with the da Vinci SP system through single-incision presternal and submental approaches in a cadaver model. While our report does not claim to give a comprehensive picture in comparison to the other robotic thyroidectomy approaches, it suggests that these presternal and submental single-port thyroidectomies compare promisingly with other currently applied robotic methods. The amount of skin flap development required for these approaches was minimal, and docking of the SP system was quick. No additional ports were required to expose the gland and complete the bilateral resection. Further studies will be needed to assess whether a presternal or submental thyroidectomy with the da Vinci SP system yields true clinical benefits in real patients.