Endoscopic thyroid surgery is an important surgical procedure for thyroid diseases. Exploring new surgical approaches remains an important direction of development for endoscopic thyroid surgery to meet the cosmetic needs of patients while treating thyroid disease.
Trans-cervico-mental angle single-port endoscopic thyroidectomy (TCMASPET), a new surgical approach, results an inconspicuous scar at the cervico-mental angle that is covered by the chin. However, no literature has reported the safety and cosmetic results of this procedure.
In this study, we reported the surgical operation steps, clinical outcomes and experience of 30 patients who underwent this procedure at our centre.
PATIENTS AND METHODS
A total of 30 patients with an average age of 36.47 ± 9.37 (22–66) years old who were admitted to our hospital between July 2020 and January 2021 were included in this study. All patients underwent pre-operative fine-needle aspiration (FNA) [Table 1]. We strictly followed the national guidelines for thyroid surgery in referring patients for surgery. Patients with thyroid cancer based on pre-operative FNA results, benign thyroid disease but with large masses or patients with a strong desire for surgery were operated upon. The inclusion and exclusion criteria for TCMASPET were similar to those for the transoral endoscopic thyroidectomy vestibule approach (TOETVA). We followed precise inclusion criteria comprising: (1) thyroid gland diameter not larger than 10 cm, (2) thyroid volume ≤45 mL, (3) main nodule size ≤50 mm, (4) benign tumour, such as a thyroid cyst, single-nodular goitre or multinodular goitre, (5) follicular neoplasm and (6) papillary microcarcinoma of the thyroid without evidence of metastasis.
The exclusion criteria were as follows: (1) unfit for surgery, (2) could not tolerate general anaesthesia, (3) previous neck surgery, ablation therapy or neck radiation, (4) substernal goitre, (5) thyroid volume >45 mL, (6) dominant nodule size >50 mm, (7) lateral cervical lymph node or distance metastasis, (8) suspicious invasion to the adjacent organs, (9) medullary carcinoma, undifferentiated thyroid carcinoma and (10) recurrent laryngeal nerve (RLN) palsy, biochemical or ultrasound signs of hyperthyroidism. All patients provided informed consent, and this study was approved by the Ethics Committee of our hospital.
Patients' position and incision selection
The incision was performed from the patient's cervico-mental angle [Figure 1a]. After an endotracheal intubation was performed and fixed, gauze was used to separate the tube from the forehead to prevent the forehead from being crushed. The surgeon was positioned on one side of the patient's head, while the assistant and nurse were positioned on either side of the head [Figure 1b]. Special surgical instruments included a single-port operator (Surgaid, Xiamen, China), a 90° angle optical fibre (Stroz, Shanghai, China), extended surgical forceps and a neural monitor (Kangji, Hangzhou, China).
After the single-port manipulator was placed in the incision [Figure 1c]. An injection of 3% epinephrine solution (1 mg/dose; Grandpharma, China; article number: H42021700) was then administered along the medial margin of the bilateral sternocleidomastoid muscles to reach the sternoclavicular region. The working space was formed by blunt dissection with a dissection rod deep into the platysma muscles until reaching the suprasternal notch. The carbon dioxide pressure was maintained at 4–6 mmHg. The anterior cervical flap ranged from the level of the hyoid bone to the level of the superior sternal notch and reached the level of the medial border of the sternocleidomastoid muscle on each side [Figure 2a]. The prelaryngeal lymph nodes were removed with an ultrasonic knife. After exposure of the thyroid, the isthmus could be cut first in the absence of nodules in the thyroid isthmus. Nerve monitoring forceps were used to identify the location devoid of superior laryngeal innervation, by detecting muscle tremor. The superior parathyroid gland could be clearly identified and retained in situ after the superior pole was cut off. The thyroid was then gently lifted to separate the thyroid dorsal fibre cord and Berry's ligament. At this time, nerve monitoring forceps were used to monitor the electric signals of the vagus nerve beside the aorta, the RLN in Berry's ligament was detected and separated with nerve monitoring forceps, and the ligament was cut by an ultrasonic knife. Then, the blood vessels in the lower pole of the thyroid were cut, followed by complete exposure of thyroid tissues and lymphatic adipose tissues in the central region [Figure 2b]. Subsequently, the inferior pole parathyroid glands could be preserved in situ, and the lymphatic adipose tissue in the central region could be removed. Lymphatic adipose tissues behind the RLN were then dissected. The contralateral thyroid and lymphoid adipose tissues in the central region could also be removed similarly.
The resected specimen was put into the special specimen bag and extracted en bloc after disassembling the single-port operator upper element. The amount of blood lost in the gauze was calculated by weighing the gauze before saline flushing of the surgical field. The stripped muscle surface fascia layer was sutured with absorbable sutures. The flap border was then illuminated by a bright spot of the probe light source, and the flap peel area was drawn on the neck skin with sterile methylene blue. Finally, a 5-mm puncture drainage tube was left in the area between the platysma myoides and the superficial layer of the deep cervical fascia through the skin incision. The platysma myoides, subcutaneous tissues and skin incisions were sutured [Figure 3a].
Observational indicators included patients' sex, age, body mass index (BMI), size and location of thyroid mass, incision length, operation time, flap separation area, superior laryngeal nerve discovery rate, RLN discovery rate, parathyroid in situ retention rate, blood loss, drainage tube withdrawal time, length of hospital stay, post-operative complications (e.g. incision infection, RLN paralysis, hypocalcaemia) and post-operative pathology.
SPSS version 20 was used for statistical analysis (IBM Corp., Armonk, NY, USA). For the characteristics and prognosis of patients, continuous variables were expressed as the mean ± standard deviation. Categorical variables were expressed as frequencies or percentages. A t-test was used for continuous variables. Pearson's Chi-square test and Fisher's exact test were used for categorical variables. P < 0.05 was considered to be statistically significant.
A total of 30 patients underwent TCMASPET. This procedure accounted for 1/20th of open thyroid surgeries and 1/4th of trans-chest-breast approach endoscopic thyroidectomies performed during the same period in our hospital. The male: Female ratio was 9:21, BMI was 22.53 ± 2.74, the maximum mass was 5.0 cm × 5.0 cm × 4.5 cm, and the relative position of the mass of the upper pole: Middle pole: Lower pole was 1:20:12. Pre-operative biopsy cytology pathology indicated 22 cases of unilateral thyroid papillary carcinoma, 2 cases of bilateral thyroid papillary carcinoma, 1 case of thyroid papillary carcinoma in the left thyroid and thyroid nodular goitre in the right thyroid, 3 cases of thyroid nodular goitre and 2 cases of thyroid adenoma. Table 1 summarises the basic characteristics and nodular characteristics of all patients. Supplementary Table 1 lists the detailed information of the patients.
All patients successfully completed TCMASPET (100%). All the specimens were extracted en bloc from the incision, without cutting the specimens into multiple pieces. The surgical incision was 2.48 ± 0.31 cm (2–3.2 cm), the average operation time was 90.00 ± 20.41 min (61–130 min), the average flap separation area was 58.53 ± 11.46 cm2 (40–90 cm2), the blood loss of patients was 10.90 ± 3.68 mL (7–22 mL), the intra-operative superior laryngeal nerve recognition rate was 81.82%, the RLN recognition rate was 100%, the rate of preservation of the superior pole parathyroid gland was 84.85%, and the rate of preservation of the inferior parathyroid excision was 78.79% [Supplementary Table 2]. The post-operative drainage tube withdrawal time was 1.8 ± 0.71 days (1–3 days), and the average length of hospital stay was 2.97 ± 0.89 days (2–5 days). The final pathology confirmed that there were 27 specimens (81.82%) of thyroid papillary carcinoma, 3 specimens (9.09%) of nodular thyroid goitre, 2 specimens (6.06%) of thyroid adenoma, and 1 specimen (3.03%) of thyroid follicular tumour. The number of lymph node dissections in the central region was 7.12 ± 3.88 (4–25). There were 16 cases (53.33%) of lymph node metastasis in the central region [Supplementary Table 2]. The chin covered the incision well when the patient was usually in front. Cosmetic results were outstanding [Figures 3b and c].
No permanent post-operative complications were observed. One patient (case 9) who received bilateral thyroidectomy developed temporary hypocalcaemia after surgery (3.33%). In this patient, blood calcium returned to normal on the 10th day after surgery. One patient (case 1) who received hemithyroidectomy developed temporary hoarseness after surgery (3.33%). In this patient, hoarseness disappeared on the 20th day after surgery [Supplementary Table 2]. Electronic laryngoscopy showed no abnormality in this patient at the first reexamination. The occurrence rate of incision infection was 0% [Supplementary Table 2].
With the increasing demand for better cosmetic results subsequent to thyroidectomy, endoscopic thyroidectomy has been widely used in the treatment of thyroid diseases requiring surgery and has achieved outstanding therapeutic and cosmetic results. However, each approach has its own drawbacks. With the premise of ensuring the safety and effectiveness of thyroidectomy, we hoped to overcome the shortcomings of the existing endoscopic thyroidectomy and achieve good cosmetic results through TCMASPET.
There was no significant difference in the number of lymph nodes dissected in TCMASPET compared with conventional open thyroidectomy (COT) (6.80 ± 2.10) (P > 0.05), the incidence of temporary hypocalcaemia was lower than that of COT (16.7%) (P < 0.05), permanent hypocalcaemia was not significantly different from that of COT (1.6%) (P > 0.05), and the incidence of temporary and permanent RLN palsy was not significantly different from that of COT (3.3%) and (0%) (P > 0.05). The length of the TCMASPET incision was significantly smaller than that of COT (4.60 ± 2.10) cm (P < 0.001), and the incision was well concealed. These results show that this procedure is as safe and effective as COT, and it also provides better cosmetic results than COT.
TOETVA has the best cosmetic results among the various approaches to thyroidectomy, but it has corresponding disadvantages. TCMASPET can overcome some of the surgical shortcomings of this procedure. (1) The chin nerve is not damaged during the procedure and therefore does not cause numbness in the lower lip. (2) Oral deformity is not a contraindication to this procedure. (3) The procedure is performed using transoral intubation, which is less difficult than the transnasal intubation used with TOETVA. (4) The operation is not disturbed by the mandible. (5) Strict oral disinfection is not required during the perioperative period. (6) The giant thyroid specimen can be extracted en bloc. In the current cohort, the largest mass we extracted intact en bloc 5.0 cm × 4.0 cm × 3.5 cm, and the largest diameter of mass extracted en bloc by TOETVA was reported to be <4 cm.
Compared to other remote-access thyroid operations, TCMASPET has the following advantages. The number of lymph nodes dissected in the central region of TCMASPET was higher than that of the trans-chest-breast approach endoscopic thyroidectomy (6.70 ± 2.00) (P < 0.05), and the location of the incision of TCMASPET was more concealed than that of the trans-chest-breast approach endoscopic thyroidectomy. The flap separation area for TCMASPET was less than that for the trans-axillary-breast approach (78.60 ± 8.60) (P < 0.05), which may reduce the production of abnormal sensations. TCMASPET can permit bilateral thyroidectomy, unlike the trans-axillary approach and trans-retroauricular approach endoscopic thyroidectomies and this could reduce the incidence of secondary surgeries.
Hybrid transoral and submental thyroidectomy (TOaST) and submental endoscopic thyroid have been previously reported. The former, with two incisions in the oral cavity, still required strict oral disinfection and prophylactic antibiotics. Both surgical procedures had more incisions than TCMASPET, therefore, establishing access was more time-consuming. In addition, both procedures were unable to extract oversized thyroid specimens unless they were divided into multiple pieces, which not only increased the operative time but also destroyed the integrity of the tumour specimens. Therefore, TCMASPET may be a more suitable approach for trans-submental thyroidectomy.
As a surgical procedure with a similar approach to TOETVA, TCMASPET has some disadvantages: (1) The surgical space is small. (2) The operation habits needed to be changed. The procedure was performed through the top-down perspective and operation order. (3) The chopsticks effect was obvious. (4) There was a blind area of lymph node dissection in area II.
This was the first systematic trial of TCMASPET. The surgical operation duration was longer than that of open surgery (90.00 ± 20.41 min) (P < 0.05) in the first ten cases. We observed that the time was decreased from case 5 (130 min) to case 28 (61 min), with a clear downward trend, which indicated the presence of a learning curve for that procedure. However, a larger sample size is required to confirm these findings. Currently, the surgical operation time was comparable with that of TOETVA with a similar approach (97.00 ± 40.50 min) (P > 0.05).
We found that the top-down procedure and the chopstick effect were the main reasons for the prolonged surgical time. To overcome these problems, we used the same approach to thyroid removal in COT as in TCMASPET to become familiar with this surgical procedure as well as the top-down anatomy. In addition, we designed longer surgical forceps to reduce the chopstick effect by using different lengths of surgical forceps. We also reduced interference between the optical cable and the surgical forceps by using a 90° angle optical cable. These improvements resulted in a significant reduction in the TCMASPET procedure time. This experience may be useful for other surgeons wishing to perform this procedure.
This study had a few limitations. First, no blind method was applied to select cases and related operations; thus, some bias might occur. Second, the small sample size of the current procedure and the fact that a single surgeon in a single centre performed all surgeries might affect the generalisability of the results. Third, a long operating time was still another area for improvement.
This is the first report on TCMASPET. We believe that TCMASPET can expand the indications for endoscopic thyroid surgery by reducing pre-operative case selection requirements, avoiding transnasal anaesthesia, reducing perioperative oral sterilisation requirements, allowing for greater specimen extraction and avoiding chin nerve injury.
Financial support and sponsorship
This study was supported by Fujian provincial health technology project (No. 2020QNA007).
Conflicts of interest
There are no conflicts of interest.
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