The transcervical approach is the gold standard technique for accessing the central neck in thyroid and parathyroid surgery; however, an anterior neck scar is inevitable (1). The presence of a central neck scar has been demonstrated to negatively impact patient quality of life (QOL) irrespective of scar severity (2-5).
Accordingly, remote-access approaches to the thyroid emerged to address the morbidity of the cervical incision. These approaches employ traditional endoscopic instruments as well as robotic surgical systems with documented efficacy and feasibility (6-9). Many of these approaches utilize dissection planes unfamiliar to traditional thyroid surgeons and are associated with increased costs, longer operative times, increased postoperative pain, technique-specific injuries, and a steep learning curve (10). Notably, these approaches are only able to displace the location of the cutaneous scar from the anterior neck to a less cosmetically conspicuous site. As a result, these techniques were slow to be adopted, especially in the West. In 2007, the New European Surgical Academy (NESA) proposed Transoral Thyroid Surgery as part of their natural orifice surgery project, which demonstrated that the central neck could be successfully accessed using a sublingual incision, sparking the development of novel thyroidectomy approaches (11-16). Subsequently, Wilhelm et al. performed a prospective proof-of-concept study on endoscopic minimally invasive thyroidectomy via the sublingual approach; this approach was ultimately abandoned due to associated serious complications such as severe tissue damage and increased conversion rate (17). In 2011, Richmon et al. described a tri-vestibular approach using a submental and subplatysmal approach (18,19). Later in 2015, Lee et al. published the first transoral robotic thyroidectomy series in four patients (20,21). Following this, Anuwong et al. published in 2016 the first case series of patients who underwent transoral endoscopic thyroidectomy vestibular approach (TOETVA) with excellent outcomes (22). The success of TOETVA has prompted many institutions around the world to adopt transoral vestibular approach (TOVA) using endoscopic or robotic surgical systems (8,23-31).
Robotic surgical systems offer theoretical advantages over endoscopic surgery, including 3D magnified visualization of the surgical field and increased dexterity with enhanced range of motion within the confined working space. In spite of this, endoscopic techniques have been more widely adapted than robotic surgical systems due to the high cost of operation, extensive learning curve, and technical limitations of robotic systems (32-34). For instance, a fourth accessory axillary incision is required when performing thyroidectomy with the da Vinci Si and Xi surgical systems (Intuitive, Inc., Sunnyvale, CA, USA) for counter-traction and drain insertion (35-37). Moreover, with the previous generation of the da Vinci robotic surgical system (Si and Xi), instrument movement is particularly unwieldly during dissection of the superior pole of the thyroid gland. As a result, an assistant familiar with the robotic system must be at the field to address arm collisions and camera positioning. In contrast, the new da Vinci single port (SP) robotic system has the capability of inserting 3 multi-jointed instruments in addition to a fully wristed 3DHD camera for high-definition visualization of the detailed anatomy of the surgical field through a 2.5 cm incision (Figure 1) (38). Therefore, the da Vinci SP system’s improved design may offer advantages in thyroid and parathyroid surgery. In this review article, we have provided a summary of existing literature on the SP system and its feasibility in the TOVA.
SP and transoral thyroid surgery vestibular approach in the literature
In 2018, the FDA approved the use of the da Vinci SP surgical system for SP urological procedures in adults. The following year, the FDA cleared the SP robot for radical tonsillectomy and tongue base resection. They stated, “The intuitive Surgical Endoscopic Instrument Control System (da Vinci SP Surgical System, Model SP1098) is intended to assist in the accurate control of Intuitive Surgical EndoWrist® SP Instruments during urologic surgical procedures that are appropriate for a SP approach and transoral otolaryngology surgical procedures in the oropharynx restricted to benign tumors and malignant tumors classified as T1 and T2…” (39). Because of limited FDA-approved indications for urological and oropharyngeal procedures, there is a paucity of original research on usage of the SP robot in endocrine procedures. Nonetheless, only three studies have explored the use of SP robot in performing the transoral thyroid surgery. Two studies were done on cadavers and the other is a 10-patient case-series. One of the studies done on cadavers is from our team and it demonstrates the preclinical feasibility study of SP surgical system in transoral thyroid surgery (40,41). The other preclinical study was conducted by Chan et al. and seeks to evaluate the next generation robotic system in transoral thyroidectomy (41). In addition, Park et al. published a case-series of 10 patients in South Korea who successfully underwent robotic transoral thyroid surgery using the da Vinci SP robotic surgical system (42).
Robotic surgical systems used in transoral thyroid surgery
The da Vinci Si and Xi systems have previously been employed in the transoral thyroidectomy vestibular approach (Figure 2) (35). The da Vinci Xi was the latest generation utilized for transoral thyroid surgery, and consequently most reported cases employed the Xi system, which often requires an additional axillary incision. Unlike Si and Xi, The SP robotic system is a SP system containing a 25 mm cannula that allows for the passage of a full-wristed endoscopic 3DHD camera along with three multi-jointed EndoWrist® SP instruments, significantly increasing the viability of robotic surgery without the need for an axillary port. The EndoWrist® SP instruments have two additional degrees of freedom compared to previous generations, facilitating enhanced external and internal ranges of motion. This allows for more precise surgical control in narrow spaces. The location and axis of the camera in the SP system offers 360 degrees of rotation and can be adjusted through the surgeon console, obviating the necessity of a bedside assistant. Additionally, the endoscope of the SP is covered by an insulator, minimizing the risk of thermal damage to surrounding tissues.
The da Vinci SP surgical system is made of three main components, similar to previous generations: the patient cart, the vision cart, and the surgeon console (Figure 3). Whereas the Xi system continues to utilize the 4-arm design, the SP is designed with only one arm with up to three flexible instruments that can emerge from this single arm (43).
Operative technique and the differences between SP and previous generations
In the preclinical study conducted by our group, we created the submental and subplatysmal space using laparoscopic instruments prior to docking the SP robot (patient cart), and CO2 gas insufflation was used to maintain the working space (33). In Chan et al., subplatysmal planes in the initial dissection were raised utilizing endoscopic guidance as in TOETVA. Then, a monopolar cautery and Kelly clamp forceps were employed to develop a plane over the periosteum of the mentum (41). Similar to Chen et al., the clinical study by Park et al. utilized monopolar cautery to create the working space with the midline incision measuring 25 mm prior to docking the robot (37).
In Park et al., following creation of the subplatysmal flap, a self-retaining retractor system was used instead of CO2 gas insufflation to maintain the working space. The patient cart containing the SP robot was docked perpendicular to the head of the surgical bed and the cannula was fixed 10 cm away from the midline incision. In both preclinical studies, CO2 gas insufflation was used to maintain the working space, similar to traditional TOVA. In our study, this was achieved by employing an Alexis (Applied Medical, Rancho Santa Margarita, CA, USA) wound retractor (XXS size) through the midline incision. The lower part of the Alexis was secured under the inferior edge of the mandible to prevent its slippage. Subsequently, we created a sealed tunnel between the working space and the SP cannula (located 6 cm from the inferior angle of the mandible) by tightly wrapping a Penrose drain around the upper end of the Alexis to prevent CO2 leakage and loss of the working space (Figure 4). A 30° endoscope was inserted through the upper slot while a ProGrasp Forceps, Maryland dissector and a monopolar curved scissors were inserted through the left, right and lower slots respectively in our study. On the other hand, in the study by Chan et al., two 5 mm cuts medial to the canines were made vertically to allow the placement of two trocars where a Maryland dissector and a hook cautery were used to create the working space deep to the platysma. The 5 mm port incisions were then closed to limit the gas leakage and an extra small wound protector (Applied Medical, Rancho Santa Margarita, CA, USA) was placed through the vestibular incision. In addition to the camera, three other instruments were used: the Maryland bipolar, fenestrated bipolar graspers, and monopolar scissors (41). Park et al. utilized only 2 incision ports (left side for Maryland forceps and the right for scissors) in addition to the camera. The transoral thyroidectomy is carried out in a similar fashion as endoscopic technique as described the literature as follows: (I) dissection of median raphe; (II) separation of strap muscles; (III) dividing the isthmus; (IV) upper pole dissection and ligation of the superior pedicle; (V) cephalocaudal dissection of the RLN; (VI) separation of the thyroid lobe off the trachea. Although the Harmonic (Harmonic Ace+, Ethicon Endo-Surgery, Cincinnati, OH, USA) is not currently included within EndoWrist SP instruments, our group successfully tried the endoscopic Harmonic HDI1000 through the lateral incision in addition to the three EndoWrist SP instruments to divide the median raphe, divide the isthmus and other steps where an energy device is typically used when performing TOETVA. Chan et al. described the use of a suction catheter through one of the ports if smoke occurs during the surgery. In addition to two EndoWrist instruments, Park YM et al. utilized a suction device and Maryland forceps inserted into the lateral incision through an endoscopic trocar that was controlled by the bedside assistant. Table 1 shows the differences between all three techniques.
Advantages and limitations of SP in transoral thyroid surgery
The advantages and limitations of SP robot in transoral thyroid surgery are summarized in Tables 2,3 respectively.
Outcomes and perioperative complications
In the series by Park et al., all cases were completed successfully using the SP robot with a mean operative time of 177 min after SP robot docking, which required a mean of 47 minutes. No postoperative RLN injury or hypoparathyroidism were reported. Three out of ten patients complained of paresthesia along the cutaneous area supplied by the mental nerve, which resolved spontaneously within 1 month. All patients were extremely satisfied with the cosmetic outcome. Additionally, in both preclinical studies, thyroidectomy was completed successfully on human cadavers with preservation of parathyroid glands and recurrent laryngeal nerves.
Over the last 3 decades proponents of minimally invasive surgery have touted the favorable surgical cosmesis in addition to potentially decreased postoperative pain, reduced length of hospital stay, and ultimately increased patient satisfaction with these procedures. While TOVA is not a minimally invasive surgery, some of the same benefits may apply (44). The introduction of the Davinci SP robot, with its advanced 3DHD camera and the versatile EndoWrist instruments, can potentially expand the selection criteria for transoral thyroid surgery to include patients with malignant nodules as well as those who might require concurrent central neck dissection. Thus, expanding these potential benefits to a greater patient population (45).
Robotic surgical systems, including the SP robot, however, have limitations that may continue to discourage widespread adoption. For instance, the cost of purchasing and maintenance is high compared to the cost of the traditional and laparoscopic techniques, limiting their availability to specialized institutions. Moreover, there is a steeper learning curve associated with robotic compared to endoscopic surgery (32,46). Furthermore, more studies are needed to evaluate mental nerve protection with use of the SP technique.
Although TOVA has proven to be safe and feasible, injury of the mental nerve is a technique-specific adverse event associated with TOVA. In TOETVA, a 15 mm midline incision is used compared to a 25 mm when using the SP robot. Further, as described in the study by Chan et al., at the end of the procedure the author noticed an increase of the vestibular incision to 35 mm. Despite this, there have been no reports of permanent mental nerve injury with the SP robot, although data is limited. In Park et al. however, only 2 instruments were used through the midline incision in addition to the camera, presumably to lower the risk of mental nerve injury. The author emphasized avoiding exceeding the premolar area when lifting the periosteal flap to stay away from the mental foremen and the main branch of the mental nerve. The mental foramen is positioned in line with longitudinal axis of the 2nd premolar tooth at the level of the vestibular fornix and about one finger breadth of the lower border of the mandible in 63% of individuals (47). Further studies are needed to evaluate the risk of mental nerve injury when performing transoral thyroid surgery and especially when making a larger incision then what is typically required with the solely endoscopic approach (48-50).
The SP robotic surgical system offers enhanced dexterity, while using a single central vestibular incision. Additionally, it allows for use a third robotic arm. These capabilities, when taken together, may increase the extent and complexity of thyroid surgery that may be performed via a vestibular approach. Limited evidence supports the widespread adoption of robots in thyroid surgery at this time.
Emerson Lee and Surya Khatri for technical editing.
Provenance and Peer Review: This article was commissioned by the Guest Editors (Jonathon Russell and Jeremy Richmon) for the series “The Management of Thyroid Tumors in 2020 and Beyond” published in Annals of Thyroid. The article was sent for external peer review organized by the Guest Editors and the editorial office.
Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at http://dx.doi.org/10.21037/aot-19-62). The series “The Management of Thyroid Tumors in 2020 and Beyond” was commissioned by the editorial office without any funding or sponsorship. JOR served as the unpaid Guest Editor of the series. RPT is a paid consultant for Medtronic and Hemostatix. The authors have no other conflicts of interest to declare.
Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.
Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.
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Cite this article as: Shaear M, Russell JO, Steck S, Liu RH, Chen LW, Razavi CR, Tufano RP. The intuitive da Vinci single port surgical system and feasibility of transoral thyroidectomy vestibular approach. Ann Thyroid 2020;5:20.