From August 2019 to December 2019, all patients who underwent thyroidectomy by the Department of Thyroid Surgery of the First Hospital of Wuhan were entered into a prospectively collected database. Our selection criteria for patients during this time period was as follows: 15–50 years of age, and thyroid mass size < 4 cm. Patients were excluded from this approach if they had a history of mandible or neck operation, lateral cervical lymph node or distant metastasis or a tumor located in the upper pole. A matched cohort of patients who underwent conventional transoral endoscopic thyroidectomy over this same time period was obtained from this prospective database by applying the same inclusion and exclusion criteria with 1:1 matching performed based on age and gender.
Data were collected on patient demographics, operative details, post-operative outcomes and final pathologic results. Time for central lymph node dissection was calculated from time of thyroid specimen removal to time of central lymph node specimen removal. Follow-up was standardized among both groups and was consistent with our practice at the time. The two groups were analyzed in terms of patient characteristics, operative clinical results and post-operative outcomes.
Statistical analysis was performed using SPSS 22.0 (SPSS, Chicago, IL, USA). The Chi-square test was employed for categorical variables and the Wilcoxon rank-sum test was used for continuous variables. A P value of <0.05 was considered statistically significant. The study was approved by The Ethical Committee of First Hospital of Wuhan.
Operative procedure of novel mini transoral endoscopic thyroid surgery
The patient was placed in a supine position, and general anesthesia was induced with orotracheal intubation using a nerve monitoring tube(Fig1.). The neck was extended with a shoulder pillow. The oral cavity was disinfected with povidone in water, and skin preparation and draping were carried out in the usual manner. All papillary thyroid carcinoma has been confirmed via fine needle aspiration before surgery. Total endoscopic thyroid surgery procedure via oral vestibular approach: The oral cavity was sterilized 3 times with 0.5% iodophor and then rinsed with normal saline 3 times. After 0.5mm vertical incision taken from the inferior square of the orbicularis oris muscle of the lower lip, the oral mucosa was opened with a sharp knife, and then the 5mm Trocar was pierced directly from the incision to the middle of the chin and pressed close to the mandible as it passed through the chin. Through the subcutaneous puncture direction of the chin, firstly vertically downward, then forward below the platysma muscle, the 5mm Trocar was used to puncture several times in the thyroid cartilage region, with the subcutaneous space initially established. About 2.5-3cm distance from the median line, and about 2cm from the labial buccal and gingival sulcus, making oblique incision of 0.5cm small incision with sharp knife, then 5mmTrocar was directly pressed against the mandible on both sides of the incision and punctured in the direction of ipsilateral sternoclavicular joint. Ensure the Trocar confluent with the middle puncture tunnel at the lower level of the platysma muscle. The 5mm Trocar was filled with CO2 with the gas pressure at 3mm Hg and the inlet flow rate at 15L/min. The electrocoagulation hook is entering from the right 5mmTrocar to cut open the loose fascia tissue below the thyroid cartilage, making the subcutaneous space gradually enlarged. The ultrasonic knife was used to further expand the space downward and bilaterally, and the sternocleidomastoid muscle was dissociated from the sternocleidomastoid muscle on both sides of the sternocleidomastoid muscle. After the construction of the cavity, the inflation pressure of CO2 is adjusted to 6mm Hg, and the inlet flow rate of CO2 is adjusted to 35L/min. The white line of the neck was cut with ultrasonic knife to expose the thyroid gland and cut the false capsule of the thyroid gland(Fig2.).
The 10mm incision was taken from the ipsilateral axillary fossa along the dermatoglyphic direction, and a blunt subcutaneous puncture device was used to puncture from the armpit along the superficial layer of the subcutaneous deep fascia to the cervical platysma muscle, close to one side of the sternocleidomastoid muscle to open the tunnel into the neck space, and then place 10mm Trocars in the armpit. Entering the endoscopic "bendable L-shaped" retractor to help retract the ribbon muscle(Fig3.).
Initially, the amount of 0.1ml carbon nanoparticles was injected into each side of the gland. After excision of anterior laryngeal lymph nodes and tapered lobes, with ultrasonic knife downward cutting of the isthmus was done to cut open berry ligament and adjust "bendable L-shaped" retractor to open the ribbon muscle above the cricothyroid joint, so as to expose the upper pole of the thyroid gland. Electrocoagulation hook was used to cut open a small part of sternal thyroid muscle, soon after, endoscopic multi-functional separation forceps with nerve monitoring function was used to avoid the injury of external branch of superior laryngeal nerve with cricothyroid muscle tremor evaluation method. Then the branches of the upper polar vessels were cut off with ultrasonic knife. The V1 signal was measured in the area of carotid sheath, then the superior parathyroid gland was bluntly separated by endoscopy, with blood supply preserved in situ. The carotid sheath was cut open and the lymphoadipose tissue in the central region was dissociated medially. The recurrent laryngeal nerve was dissected below the inferior pole of the thyroid and the R1 signal was detected. Dissect with endoscopic fine separation forceps to bluntly separate the inferior parathyroid gland, and try to retain the blood supply of the inferior parathyroid gland in situ. If the inferior parathyroid gland cannot be preserved in situ, it can be actively removed and transplanted into the sternocleidomastoid muscle or deltoid muscle. Then go back to the laryngeal point and dissect the recurrent laryngeal nerve, continue to cut off part of the suspension ligament, bluntly separate the recurrent laryngeal nerve from the gland, and then completely remove the thyroid tissue near the cricothyroid joint attached to the trachea with an ultrasonic knife. Note that the head of the ultrasonic knife should maintain a distance above 3mm from the recurrent laryngeal nerve.
Next, the recurrent laryngeal nerve was dissected retrograde along the shape of the nerve with endoscopic separation forceps, and the nerve tunnel was opened to block remove from the first and second layers of lymphoid adipose tissue in the ipsilateral central area, reaching the innominate artery and thymus below. Then preserve the specimen with a specimen bag. The specimen bag was removed from the axillary incision. Right thyroid cancer also requires a dissection of the third layer of central lymphoid adipose tissue, the lymph node behind the recurrent laryngeal nerve. With blunt separation close to the recurrent laryngeal nerve, cut and push with ultrasonic knife to remove the lymphoid adipose tissue in front of the esophagus, take out the free lymphoid adipose tissue from the back of the nerve and remove the whole piece as far as possible. At this time, we can use the "bendable L-shaped" retractor to push the common carotid artery outward to facilitate our next lower dissection (Fig4.).
The specimen was put into a specimen bag and removed from the axillary incision. Following up cleaning, the R2 signal and V2 signal were monitored and compared with R1 and V1 to see whether the signal was decreased. If the signal is not significantly reduced, the function of the recurrent laryngeal nerve is well protected. Rinse the operation field with a large amount of distilled water, carefully check the hemostasis, suture the white line, place a high negative pressure drainage tube in the operation cavity, draw out from the axillary incision, and fix the drainage tube in the skin layer. The 5mm Trocar on both sides of the oral vestibule and the 5mm Trocar in the middle were withdrawn in turn. The three 0.5cm oral mucosal incisions were intermittently sutured with absorbable lines, and each incision was sutured with two stitches. Finally, the oral cavity was sterilized 3 times with 0.5% iodophor and then rinsed with normal saline 3 times.