Application of Straight Line Tunnel With Less Subcutaneous Separation in Transthoracic Endoscopic Thyroidectomy

Patients

Between March 2011 and June 2014, a total of 40 patients underwent transthoracic thyroid surgery in Shanghai Shuguang Hospital. The age of patients ranged from 25 to 54 years (mean age: 36 years; 29 women and 11 men). Preoperative ultrasound and computed tomography scans revealed thyroid mass in left lobe (12 cases), in right lobe (23 cases), and in both (5 cases). The diameter of the thyroid mass ranged from 1.2 to 6.5cm (mean 3.8 ± 2.5 cm). As fine-needle aspiration cytology was not routinely performed, preoperative diagnoses were nodular goiter (n = 20), thyroid adenoma (n = 16), and thyroid calcification (n = 4). (There were also 3 punctate calcifications and 1 small focus calcification.) Eligibility criteria were benign thyroid nodules (diameter < 5cm) and papillary microcarcinoma diagnosed by fine-needle aspiration cytology. Exclusion criteria were a history of neck surgery and radiotherapy; thyroiditis diagnosed by preoperative biochemistry or ultrasound; and autoimmune or endocrine diseases.³

Surgical technique

All patients were prepared for endoscopic thyroidectomy under general anesthesia. After the patient was placed in a supine position, a pillow was placed beneath the shoulder to extend the head and neck. The operator and scope assistant stood on the right side of the patient, the first assistant stood on the left side of the patient, and the monitors were placed on the head side of the patient. A 10-mm incision was made in the intersection point of median thoracic line and bilateral nipples. A self-made metal rod with blunt round end was used to create a straight-line tunnel toward the sternal notch. Two 5-mm incisions were made in the intersection point of the bilateral midclavicular line and the second rib. Also two 5-mm metal rods were used to create straight-line tunnels. Three straight-line tunnels met at suprasternal fossa and no other thoracic wall dissection was necessary (Fig. 1 and Fig. 2).

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The 3 tunnels should be between the superficial layer of thoracic fascia and the deep layer of superficial fascia to prevent mammary or pectoralis major injuries. After the blunt dissection, 3e trocars were inserted through each tunnel. Carbon dioxide gas was injected with a pressure of 8 mmHg. A 30° 10-mm endoscope was inserted through the middle 10-mm trocar; an ultrasonic scalpel and a grasping forceps were inserted through two 5-mm trocars. Subplatysmal space was dissected to create a working space from suprasternal fossa to the thyroid cartilage level and laterally to the medial edge of sternocleidomastoid muscles (Fig. 3 and Fig. 4).

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Cervical linea alba was dissected and the thyroid anterior muscles were separated by ultrasonic scalpel, and then the anterior cervical muscle group was retracted with suture to expose the thyroid tissue. The rest of the procedure was the same as that for endoscopic thyroidectomy. The specimen was pulled out in an endo-bag through the endoscope port site and a drainage tube was routinely placed.

Analysis of straight-line tunnel

Transthoracic endoscopic thyroidectomy is a modified operation type of transareolar approach. The aim of modification is to shorten the length between incision and surgical field and reduce the range of thoracic skin flap. However, some patients who underwent transthoracic endoscopic thyroidectomy still suffered from subcutaneous seroma and skin contracture. Subcutaneous seroma mostly appeared in breast and axillary approach with an incidence of 1.1% to 1.2%.¹⁰ It always occurred 3 to 5 days after operation, which was caused by accumulated lymph and serum under the thoracic skin flap. Mainly clinical manifestation included local swelling, pain, and undulating sensation. The diagnosis could be identified if ultrasonic or CT scan revealed subcutaneous liquid dark area. We were always trying to minimize the range of skip flap when performing transthoracic endoscopic thyroidectomy. A mature endoscopic operation type needs not only suitable working space but also minimal tissue injury. After a large amount of operation practice, we made a consensus as follows: (1) 3 self-made metal rods were used to create straight-line tunnels and thoracic wall dissection was no longer necessary before they met at the suprasternal fossa; (2) the upper border of cervical skip flap (unilateral lesion) was the level of thyroid cartilage, the lateral border was the sternocleidomastoid and the medial border was 2 cm across the linea alba cervicalis. We believed the range of dissection was enough to perform almost all of the transthoracic endoscopic thyroidectomy. The total area of skin flap, which was about 6*8 cm², including the range of cervical dissection and 3 tunnels, was almost the same size of conventional thyroidectomy. Since this kind of operation type had avoided a cervical incision, it achieved a good balance of cosmetic results and minimal invasion. Patients who underwent such procedures were satisfied with the outcomes without any complications of subcutaneous ecchymosis, seroma, or skin contracture. As for the surgical details, we considered that (1) a metal rod should be rotating, pushed toward one direction with a relatively low speed to create a straight-line tunnel, because high speed pushing would cause direction biasing; (2) push gently, otherwise the end of metal rod would enter into another level; (3) rub the ends of 3 metal rods at the meeting point (point D in Fig. 1) repeatedly to make fully contact. We might not have been able to find the ultrasonic scalpel if the 3 tunnels have been at different levels; (4) when the visual field is hindered by subcutaneous fibers, use an ultrasonic scalpel to dissect the tunnel toward the endoscopy rather than creating a new tunnel.

Prevention of complications

Recurrent laryngeal nerve (RLN) injury is one of the most common complications of endoscopic thyroidectomy. However, with improved visualization and amplification of the endoscope, the recurrent laryngeal nerve was convenient to expose its position and course by skilled surgeons. With the accumulations of surgeons' experiences, the incidence of direct RLN injuries is decreasing. More and more RLN injuries are indirect thermal injuries caused by ultrasonic scalpel. According to our experience, ultrasonic scalpel should keep some distance from RLN while maintaining sufficient surgical extension; the functional knife head should be kept away from RLN for at least 2 mm¹¹ and coagulating time should be reduced as soon as possible while operating near RLN. When performing lobectomy, routine identification of RLN can help to decrease the rate of RLN injury.¹² In Korea, 55% of the surgeons thought that there were not significant differences between conventional and endoscopic approaches for the complications such as RLN injury and hypocalcemia.¹³ Parathyroid injury may occur in some total thyroidectomies. Parathyroid glands show pale orange red on the screen while adipose tissues show yellow. With the help of a good endoscopic vision, we can easily recognize them by different colors. Although the parathyroid glands can be preserved, the blood supply may be affected by the thermal damage of ultrasonic scalpel. Once it occurs, patients may suffer from temporary postoperative hypocalcemia. Most patients got a spontaneous recovery and those with severe symptoms could be treated by intravenous infusion of calcium gluconate. As for the complication of bleeding, surgeons always pay more attention to the remaining gland. Hemorrhage of tunnels may be neglected due to the compression of trocars. We always check the subcutaneous tunnels carefully after removing the trocars. Flushing with epinephrine saline may be an alternative hemostasis method with a satisfactory effect.