|Year : 2020 | Volume
| Issue : 2 | Page : 53-60
Transoral Robotic Thyroid Surgery: Technical Considerations
Department of Otolaryngology-Head and Neck Surgery, College of Medicine, Hanyang University, Seoul, Republic of Korea
|Date of Submission||25-Jun-2020|
|Date of Acceptance||07-Jul-2020|
|Date of Web Publication||8-Dec-2020|
Department of Otolaryngology-Head and Neck Surgery, College of Medicine, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 04763
Republic of Korea
Source of Support: None, Conflict of Interest: None
Recently, many surgeons worldwide have adopted the transoral thyroidectomy approach owing to the associated advantages of less surgical morbidity, excellent cosmesis, and superior postoperative vocal outcomes. Specifically, transoral robotic thyroidectomy, in which a surgical robot is used, has been performed to hide or avoid visible neck scars and overcome the limitations associated with the endoscopic procedure. The transoral robotic thyroidectomy technique involves creation of three oral vestibular incisions and use of an additional axillary port, if indicated. Transoral robotic thyroidectomy is feasible and comparable to conventional transcervical thyroidectomy for highly selected patients. However, some unusual complications, such as CO2 embolism, mental nerve injury, surgical site infection, and skin burn and trauma, are noted. Appropriate patient selection is important for the safety and success of this surgery.
Keywords: Endoscopic thyroidectomy, remote access thyroidectomy, robotic thyroidectomy, transoral thyroidectomy
|How to cite this article:|
Tae K. Transoral Robotic Thyroid Surgery: Technical Considerations. J Head Neck Physicians Surg 2020;8:53-60
| Introduction|| |
Visible neck scars and cosmesis are major concerns after thyroidectomy.,, In the past 20 years, various remote access robotic and endoscopic thyroidectomy techniques have been developed to avoid or hide visible neck scars.,, Of these, the transoral approach has been recently highlighted and adopted by many surgeons worldwide owing to the numerous associated advantages.,,,,,,,,,,, The most significant advantages of transoral thyroidectomy are low surgical morbidity, superior postoperative cosmesis, and good preservation of functional voice. Song et al. reported the highest and broadest frequency and pitch range in the transoral robotic thyroidectomy group compared to that in the conventional transcervical group postoperatively.
The transoral approach is considered a type of natural orifice transluminal endoscopic surgery. The invasiveness of the transoral approach to create a working space is less than that of the bilateral axillo-breast approach and transaxillary approach because the distance from the oral vestibular incisions to the thyroid gland is small.,, Postoperative cosmesis is potentially better than that noted with other remote access procedures because no visible neck scar is observed after this procedure. The transoral approach enables surgeons to perform bilateral total thyroidectomy because it is a midline approach. In addition, complete central neck dissection is possible, even up to level VII because it is a superior to inferior direction approach.,, Here, I review the history of surgical techniques, relevant tips and tricks, and complications and safety of the transoral robotic thyroidectomy.
| History and Evolution of The Transoral Thyroidectomy Techniques|| |
The concept of transoral approach was first introduced by Witzel et al. in cadavers and a pig model in 2008. They created a 15-mm incision in the central sublingual area to place a modified axilloscope and two 3.5-mm lateral incisions on the external neck skin, 15 mm below the larynx, to insert two endoscopic instruments. Karakas et al. introduced another technique of transoral approach in pigs and cadavers in 2009. They created a 2-cm oral mucosal incision on the lateral floor of the mouth and approached the thyroid and parathyroid glands obliquely through lateral to medial direction. They attempted this technique when performing parathyroidectomy in a few human patients. However, the working space was narrow, and unusual complications, such as hypoglossal nerve injury, were noted when this technique was performed., None of the patients wanted to undergo this technique; hence, this technique is no longer used in the clinical setting.
Benhidjeb et al. and Wilhelm et al. performed transoral endoscopic thyroidectomy in cadavers and humans, using one sublingual port and two oral vestibular ports in 2009 and 2010, respectively., This technique was initially attractive. However, it was not widely used; this technique has been performed only in some centers in Germany and China.,
The transoral vestibular approach using three oral vestibular incisions was first described by Richmon et al. in a cadaveric model using the da Vinci surgical system (Intuitive Surgical, Inc., Sunnyvale, CA, USA) in 2011. This approach provided the basics of the transoral vestibular approach using endoscopy or surgical robots, which are commonly used presently.
In 2013, Nakajo et al. performed gasless transoral video-assisted neck surgery using a single 2.5-cm incision in the central oral vestibule. They used the wire and external retraction system to maintain the working space without CO2 insufflation. However, they reported a high rate of mental nerve injury postoperatively, which might be associated with the 2.5-cm long incision in the mid-portion of the oral vestibule. Woo reported a case of transoral endoscopic thyroidectomy using a frenotomy incision in 2014. He created a single sublingual vertical incision on the lingual frenulum. However, the working space was very narrow with this technique; hence, it is not used in the clinical settings anymore.
Transoral endoscopic thyroidectomy via the oral vestibular approach in human patients was first reported by Wang et al. in China in 2014. However, the oral vestibular approach was popularized after publication of the report of 60 cases by Anuwong under the name “Transoral Endoscopic Thyroidectomy Vestibular Approach,” in 2016. In 2018, Kim et al. reported the feasibility and early experiences of transoral robotic thyroidectomy through 3 oral vestibular ports and an additional axillary port using the da Vinci Si surgical system (Intuitive Surgical, Inc., Sunnyvale, CA, USA) in humans. Studies conducted by Razavi et al. and Tae et al. compared the robotic procedure to the endoscopic procedure with respect to the transoral vestibular approach in 2018 and 2019, respectively., They showed that the surgical outcomes were not different between the robotic and endoscopic procedures, except for the operative time. The operative time for the robotic procedure was longer than that for the endoscopic procedure.,
In 2019, Park et al. introduced the gasless transoral endoscopic vestibular approach for thyroidectomy in which the external retraction system without CO2 insufflation was used. The advantage of the gasless method is the absence of complications associated with CO2 insufflation. However, the placement of the external retractor blade narrowed the central oral port space. Therefore, they used a small 5-mm endoscope instead of a 10-mm endoscope because of the insufficient space. In addition, it is not easy to maintain a good working space when using the gasless method compared to that when using the CO2 insufflation method. The surgical view is inferior to that noted with the CO2 insufflation method. Transoral robotic thyroidectomy performed using the da Vinci single port (SP) surgical system (Intuitive Surgical, Inc., Sunnyvale, CA, USA) via the CO2 insufflation or gasless method was introduced in 2019.,, However, the da Vinci SP system does not offer major advantages over the da Vinci Si or Xi system for transoral thyroidectomy. Further studies are necessary to determine the role and efficacy of gasless transoral endoscopic thyroidectomy and transoral robotic thyroidectomy using the da Vinci SP system.
| Indications and Contraindications|| |
The indications of transoral thyroidectomy can be expanded according to the experience of the surgeon and advancements in the surgical techniques. The indications for transoral thyroidectomy may include benign thyroid nodules measuring <5 cm in diameter and differentiated thyroid carcinomas measuring <3 cm with or without minimal extrathyroidal extension and central compartment lymph node metastasis., In the transoral approach, the size of the tumor and volume of the thyroid itself can influence the surgical indication because it is difficult to remove a sizable surgical specimen through a small oral incision port. There are no absolute criteria for transoral thyroidectomy with respect to the tumor size and thyroid volume. However, the ideal tumor size and thyroid volume for transoral thyroidectomy may be <2 cm and 40 ml, respectively, when taking out the surgical specimen through the central oral incision port. However, if the axillary port is used, the tumor size criteria can be extended for larger tumors.
The exclusion criteria for transoral thyroidectomy include gross extrathyroidal extension invading the surrounding structures and large and multiple metastatic lymph nodes in the lateral compartment. Large goiters with Grave’s disease or Hashimoto’s thyroiditis may be relative contraindications owing to increased intraoperative bleeding and fragility of the thyroid tissue. Patients with a history of previous neck or thyroid surgery or neck irradiation are also contraindicated for transoral thyroidectomy.,
| Surgical Procedures of Transoral Robotic Thyroidectomy|| |
Positioning of the patient
The patient is placed in a supine position. Orotracheal intubation using a nerve monitoring tube is performed, and general anesthesia is induced. Usually, nasotracheal intubation is not necessary. Orotracheal intubation does not interfere with the surgery, and it is better to place a nerve monitoring tube. The neck is extended using a shoulder pillow, and the patient’s head is fixed to the operating table using plaster to prevent rotation during the operation. The oral cavity is disinfected with povidone solution, and skin preparation and draping are performed in the usual manner.
Intraoperative neural monitoring
The standardized intermittent intraoperative neural monitoring (IONM) protocol for the recurrent laryngeal nerve (RLN) and the vagus nerve recommended by the International Neural Monitoring Study Group is performed. In addition, neural monitoring of the external branch of the superior laryngeal nerve (EBSLN) is done routinely by obtaining V1-S1-S2-R1-R2-V2 signals, in principle. We used the robotic instrument itself as a stimulating probe by connecting it to the neural monitoring system.
Rocuronium is used as the nondepolarizing muscle relaxant, with the administration of a 5 mg/kg dose once at the induction of anesthesia. The C2 NerveMonitor with Laryngeal Electrode Select (Inomed Medizintechnik GmbH, Germany) is used for IONM. The proper position of the laryngeal electrode and neck extension are routinely checked after intubation using laryngofiberscopy.
Design of oral incisions and elevation of the skin flap
A 1.5–2-cm central incision is created near the base of the lower lip frenulum, and two lateral incisions are crated close to the oral commissure to avoid mental nerve injury [Figure 1]. After the central mucosal incision is created using monopolar electrocautery, dissection is performed to the chin over the periosteum of the mandible and extended to the submental area using clamps. Blunt dissection of the submental area is performed with a Hegar dilator in the midline and on both sides of the midline in a fan-like shape. We no longer inject diluted epinephrine for hydrodissection in the submental area and the central neck, because we have found from our early experiences that hydrodissection is not helpful for the elevation of the skin flap. A 12-mm trocar for the endoscope is inserted, and carbon dioxide is insufflated at 5–6 mmHg pressure. The lateral mucosal incisions are created, and 5 mL of epinephrine diluted in saline (1:400,000) is injected over the periosteum of the mandible with a Veress needle syringe for hydrodissection. Two trocars are inserted through the lateral oral vestibular incisions on either side of the endoscope. When inserting the two lateral trocars, care is taken not to perforate the facial skin because the skin and soft tissue of the lower lip and chin are usually thin. This explains why we use diluted epinephrine for hydrodissection in this area. It helps to prevent face skin perforation.
|Figure 1: Oral incisions created during transoral robotic thyroidectomy. Two lateral incisions are created close to the oral commissure|
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After inserting the three trocars [Figure 2], a 30° endoscope is inserted centrally. Laparoscopic dissectors and a hook bovie are then inserted through the lateral trocars. The exact plane of the subplatysmal layer is identified in the submental area, and the skin flap is elevated through this plane using the laparoscopic dissectors and hook bovie [Figure 3].
|Figure 2: A 12-mm trocar is inserted for a 30° rigid endoscope, and two lateral 8-mm trocars are inserted for the robotic instruments|
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|Figure 3: The skin flap is elevated under the endoscope in the plane of the subplatysmal layer|
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Docking of the da Vinci surgical robot
After the elevation of the skin flap in the submental area, a da Vinci Si surgical system (Intuitive Surgical, Inc., Sunnyvale, CA, USA) is placed and docked on the left lateral side of the patient. A dual-channel 30° endoscope is placed face-down in the central oral port, and two robotic instruments, either monopolar scissors or Maryland forceps, are placed on either side of the endoscope. After docking the da Vinci robot, the elevation of the skin flap is continued inferiorly to the level of the sternal notch and laterally to the lateral border of the sternocleidomastoid muscle. If we use the da Vinci robot, we can easily elevate the skin flap in the exact plane of the subplatysmal layer using a 3-dimensional magnified view and wristed robotic instruments. We do not use the external hanging suture to suspend the skin flap; usually it is not necessary. On creating a sufficient working space, a 1-cm incision is created in the right axillary fossa and a long robotic cannula is inserted, if indicated. A third robotic instrument, such as Cardinal forceps, is inserted through the right axillary port [Figure 4].
|Figure 4: Docking of the da Vinci surgical robot. Three trocars for an endoscope and two robotic instruments are placed in the oral vestibule, and a fourth robotic trocar for a third robotic instrument is inserted through the right axillary incision|
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Robotic dissection for thyroid lobectomy
The midline fascia between the strap muscles is divided [Figure 5]a and the sternohyoid and sternothyroid muscles are dissected to expose the thyroid gland [Figure 5]b. The pyramidal lobe is dissected, and the isthmus is divided and dissected from the trachea for better mobilization of the thyroid gland [Figure 5]c. The superior pole of the thyroid gland is dissected from the larynx in the avascular space, and the superior thyroid vessels are cut individually close to the thyroid gland to preserve the EBSLN [Figure 5]d. The superior parathyroid gland is identified and carefully preserved with an intact blood supply [Figure 5]e. The thyroid gland is then retracted medially, and the middle thyroid vein is divided. Then, the RLN is identified and confirmed using an IONM stimulating probe [Figure 5]f. The perithyroidal soft tissue is dissected while tracing the RLN with great care to preserve it [Figure 5]g. The inferior parathyroid gland is also preserved. The Berry’s ligament is dissected, and the thyroid lobectomy is completed [Figure 5]h.
|Figure 5: Procedures for transoral robotic thyroidectomy. (a) The fascia between the strap muscles is divided. (b) The sternohyoid and sternothyroid muscles are dissected to expose the thyroid lobe. (c) The isthmus is divided and dissected from the trachea for better mobilization of the thyroid gland. (d) The superior thyroid vessels are divided individually close to the thyroid gland. (e) The superior parathyroid gland is identified and preserved. (f) The recurrent laryngeal nerve is identified using an intraoperative nerve monitoring probe. (g) The perithyroidal soft tissue is dissected, while tracing the recurrent laryngeal nerve with great care to preserve it. (h) Surgical view after completion of thyroidectomy. The recurrent laryngeal nerve and superior parathyroid gland are well-preserved. (i) The resected specimen is extracted in an endobag through the axillary port. (j) The strap muscles are re-approximated using V-Lock sutures. Arrow heads: Recurrent laryngeal nerve; Arrows: Superior parathyroid gland|
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Removal of the surgical specimens and closure of the wound
The resected specimen is extracted using a plastic endobag through the central oral incision port or the axillary port [Figure 5]i. In the cases of total thyroidectomy, contralateral lobectomy is performed in a similar manner. The strap muscles are re-approximated using V-Lock sutures [Figure 5]j. The oral vestibular mucosal incisions are closed with resorbable sutures, and no drain is inserted.
| Complications of Transoral Thyroidectomy|| |
The surgical outcomes and safety of transoral robotic or endoscopic thyroidectomy are feasible and comparable to those of conventional thyroidectomy. However, the complication rates of transoral thyroidectomy might be potentially higher, especially during the learning curve and in the case of low-volume surgeons and low-volume centers. The incidence of common complications, including RLN palsy, hypoparathyroidism, hematoma, and seroma, has been reported as being similar to that of conventional thyroidectomy.,,,,,,, There are additional complications associated with the transoral approach including mental nerve injury, CO2 embolism, surgical site infection, skin burns and trauma, tracheal injury, dimpling of the chin, and oral commissure tearing.,,,,,,,,,,,,,,,,,,,
CO2 embolism and subcutaneous emphysema
The CO2 insufflation method can result in CO2-related complications such as subcutaneous emphysema, hypercapnia, respiratory acidosis, cerebral edema, and CO2 embolism., CO2 embolism, a serious intraoperative complication that could lead to cardiac arrest requiring resuscitation, can happen in transoral thyroidectomy although the incidence is low. CO2 embolism develops mainly due to tearing of the anterior jugular vein during skin flap elevation.,, To prevent CO2 embolism, it is crucial to perform blunt dissection with a dilator only in the submental area, in order to minimize the chance of tearing the anterior jugular vein., In addition, it is important to identify the platysma muscle and elevate the skin flap precisely in the plane of the subplatysmal layer under the guidance of the endoscope. During skin flap elevation, an energy-based device is safer than a monopolar bovie because it divides and seals off the vessel rather than cutting it. Moreover, the CO2 insufflation pressure should be set as low as possible, usually at 4–6 mmHg, and the CO2 flow rate should be <8–10 L/min.
Subcutaneous emphysema, presenting as crepitus in the neck and upper chest area, can develop after transoral thyroidectomy. However, in most cases, subcutaneous emphysema resolves spontaneously with conservative management. The possible causes of subcutaneous emphysema may include high CO2 pressure and long operative time. Therefore, surgery should be completed reasonably quickly to prevent the development of emphysema.
Mental nerve injury
A unique complication associated with the transoral approach is mental nerve injury. Mental nerve injury causes unilateral or bilateral numbness of the lower lip and chin, and the medial and lateral inferior labial branches of the mental nerve are vulnerable to surgical trauma. The incidence of mental nerve injury varies greatly in previously published studies. Mental nerve injury is poorly defined, with some authors defining it as severe sensory loss in the chin, while others define it as any mild or moderate sensory disturbance and paresthesia. Some studies published when the transoral thyroidectomy procedure was initially initiated demonstrate a high rate of mental nerve injury ranging from 75% to 100%.,, This high rate of mental nerve injury may be related to the learning curve and technical complexity of the procedure. However, recent papers reported lower rates of mental nerve injury ranging from 0% to 2.5%.,,
Tae et al. objectively evaluated the sensory changes in the chin and neck after transoral thyroidectomy using the Semmes-Weinstein monofilaments test. They did not report mental nerve injury, and the pressure thresholds of the chin and lower lip innervated by the mental nerve were not different preoperatively and postoperatively. Only approximately 10% of the patients showed a transient mild sensory disturbance on the chin at 1 week postoperatively, and the baseline condition was restored at 1 month postoperatively. These results provide evidence that mental nerve damage rarely occurs during transoral thyroidectomy, if the operation is performed through the oral vestibular incisions created at the appropriate sites with minimal soft tissue dissection in the chin area. In addition to the main causes of mental nerve injury, such as inappropriate oral vestibular incisions and direct nerve damage, injury can also be caused by mechanical stretching and compression owing to a large sized trocar, trocar movement during the operation, and long operative times.,, Therefore, to avoid mental nerve injury, the oral vestibular incisions should be created at the appropriate sites and soft-tissue dissection and damage of the chin and central oral vestibular area should be minimized.
Surgical site infection
One important and interesting complication in the transoral approach is surgical site infection. This could be due to the numerous bacteria in the oral cavity, even in the normal flora. Several studies have reported only a few cases of wound infections after transoral thyroidectomy.,,,,,,, The rates of surgical site infection in a few meta-analyses were also very low (0.1%–1%).,,, However, Tae et al. reported a high incidence (6%) of surgical site infection, including even mild swelling and skin redness, after transoral thyroidectomy, despite the 1- to 2-week routine use of antibiotics preoperatively and postoperatively. There is no standard definition for surgical site infection. However, we should be aware of the possibility of surgical site infection after transoral thyroidectomy, and appropriate antibiotics should be administered preoperatively and postoperatively.
Skin perforation, burn, and trauma
Skin flap perforation in the anterior neck area, lower lip, and chin can occur in transoral thyroidectomy. Care should be taken not to perforate the skin when elevating the skin flap using a monopolar bovie or when inserting the lateral trocars, especially in those patients with a thin skin.
In addition, there were skin flap burns and injuries in transoral thyroidectomy due to mechanical trauma and heating from the endoscope tip., Although most skin burns and traumas are mild, and resolve without any sequela, some severe burns and trauma can result in skin pigmentation, contracture, and dimpling. Therefore, we need to be careful to avoid burning and injuring the skin flap during the transoral procedure.
Conversion of the procedure
Sometimes, among the transoral robotic and endoscopic procedures, there are conversions to the conventional transcervical approach or other types of remote access thyroidectomies. The possible causes of conversion may include severe CO2 embolism, uncontrollable intraoperative bleeding, and inability to remove the entire tumor.,
| Comparison of The Endoscopic And Robotic Procedures in The Transoral Approach|| |
In the transoral approach through the oral vestibule, despite the many advantages of the robotic procedure, the endoscopic procedure is commonly performed worldwide. This phenomenon might be related to the high cost of the robotic procedure and the robotic system, and the availability and need for training on the surgical robot. In addition, the robotic procedure takes more time than the endoscopic procedure in transoral thyroidectomy.,
However, transoral robotic thyroidectomy using the da Vinci Si or Xi system has many advantages than the transoral endoscopic procedure.,, The main advantages of the da Vinci surgical system are the three-dimensional magnified view and innovative instrumentation with extended freedom of motion. In addition, it provides the ability to use three robotic instruments simultaneously with the axillary port to obtain counter traction. Counter traction is crucial, as it facilitates dissection and improves surgical dexterity and ergonomics with the robotic procedure. In addition, it is very convenient when taking out the large surgical specimens through the axillary port.
| Conclusions|| |
Transoral robotic thyroidectomy is feasible and safe for highly selected patients. However, some unusual complications, such as CO2 embolism, mental nerve injury, surgical site infection, and skin burns and trauma, are noted. Appropriate patient selection and recognition of the possibility of unusual complications are important for patient safety and success of the surgery. An appropriate training program is also definitively required.
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Conflicts of interest
There are no conflicts of interest.
This material has never been published and is not currently under evaluation in any other peer reviewed publication.
The permission was taken from Institutional Ethics Committee prior to starting the project. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]