Thyroid surgery has a history of more than 100 years, with pioneers of thyroid surgery such as Kocher, Mayo, Lahey, Clark, Thompson, Schwated, Lore, Reeve, and Delbridge. Especially in recent decades, the technical development of thyroid surgery has become increasingly sophisticated. The main change in surgical technique has been the move from “lateral dissection” to “perineural dissection”, which has made it possible to deal with the recurrent laryngeal nerve (RLN), to identify the sympathetic-laryngeal nerve anastomotic branch, to routinely identify the external branch of the superior laryngeal nerve (EBSLN), and how to perform a surgical procedure on the EBSLN. EBSLN) and how to protect the parathyroid glands intraoperatively has become a focal point. In this article, we will discuss surgical techniques in thyroid surgery in terms of the history of thyroid surgery and surgical techniques. A. History of thyroid surgery The earliest credible record of thyroid surgery comes from the Salerno School in the 13th century, when the techniques used were limited to branding with hot irons, ligating with thread, etc., and the residual thyroid tissue quickly recurred. 1808, Guillaume Dupuytren of Paris first better described the anatomy in total thyroid surgery, which he described as ligating the four Theodore Billroth began the modern era of thyroid surgery and initially, in Zurich, he calculated that this operation had a mortality rate of 40 and therefore abandoned it. However, by 1877, when he moved to Vienna, many of the problems regarding sepsis were resolved, so he reported a mortality rate of only 5 for thyroid surgery. billroth used a conservative subtotal thyroidectomy, however, despite the fact that hypothyroidism and hand-foot convulsions were rare, there was still a significant mortality rate, and 36 patients had damage to the recurrent laryngeal nerve. theodore kocher reported 101 thyroid operations in 1883, including 18 total thyroidectomies. There were no recurrences, and in 1895 he reported 900 thyroid operations with a mortality rate of 1 and very few complications, for which he was awarded the Nobel Prize in 1909 – the first surgeon to receive this distinction. At the same time, the blood supply to the parathyroid glands was described in detail by Halsted and Evans in 1907, and in 1926 Lahey was the first to perform successful parathyroid autotransplantation in patients with partial thyroidectomy. In 1937 Coller and Boyden suggested ligating the superior pole branch vessels of the thyroid to protect the superior laryngeal nerve (SLN), and by 2004 Page in France formally introduced the concept of the cricothyroid gap. The recurrent laryngeal nerve (RLN) was first proposed by Frank Lahey in 1938 to expose (expose) the recurrent laryngeal nerve during thyroid surgery. Video-Assisted Thyroidectomy VAT (Video-Assisted Thyroidectomy VAT) Minimally invasive thyroid surgery was introduced by Gagner in 1996 and developed by Miccoli in 1997 to Minimally Invasive Thyroidectomy MIT (endoscopic assisted thyroid surgery with small incisions in the neck). Caspsular dissection was first proposed by Halsted in 1907, until 1973 when Thompson introduced this technique in detail in the United States, and then further developed by Reeve (1987) and Delbridge (1992). The technique of thyroid surgical envelope dissection, which is a great innovation in modern thyroid surgical techniques. II. Thyroid lobectomy procedure The standard thyroid lobectomy is the most basic procedure in thyroid surgery. Mastering the standard thyroid lobectomy also means that it is possible to perform all thyroid surgeries. This is because a total thyroidectomy is also a bilateral lobectomy of the thyroid gland. The following is a systematic description of the thyroid lobectomy procedure. 2.1 Anesthesia and position With the continuous development of thyroid surgery techniques, general anesthesia is increasingly used in thyroid surgery. Anesthesia such as cervical plexus anesthesia and local anesthesia will eventually be withdrawn from the thyroid surgery scene. General anesthesia has an advantage that cannot be matched by cervical plexus and local anesthesia: in this anesthesia state, even if the operation takes a long time, the patient is in no pain or discomfort, and the operator should not worry about the patient’s cooperation during the operation. Moreover, with the continuous improvement of the anatomical skills of the recurrent laryngeal nerve, intraoperative sound testing of the patient is no longer necessary. The position is usually supine with the anesthetized patient in a supine position, with a support object placed under the shoulders so that the head is extended, care should be taken not to over extend the neck to avoid postoperative discomfort, especially in those with cervical spondylosis. 2.2 Incision, electric knife and magnification Nowadays, the incision of thyroid surgery is generally made by low collar incision, after routine disinfection and towel laying, generally along the skin pattern of the neck, the length of the incision is decided according to the size of the tumor, generally 5-6cm can be used. The advantages of using this kind of electric knife are as follows: 1) the operator’s hand can be more flexible and convenient without having to be bound to operate the electric knife or electric coagulation; 2) thyroid surgery is originally a fine operation, and the use of a sharp blade can make the contact surface between the electric knife and the tissue smaller and cause less damage to the tissue, so that many finer operations can be completed. Precise operation of the thyroid gland was first proposed by Riddel in 1970, and microsurgical thyroidectomy was introduced by Nielsen in Denmark in 1998, and I now use a 2.5x surgical magnification to do the surgery. 2.3 The procedure is performed by cutting the skin to the level of the broad cervical muscle and the strap muscle, then separating the flap from the broad cervical muscle on the superficial surface of the deep cervical fascia upward to slightly above the incision of the thyroid cartilage, and downward without dividing or slightly dividing the flap to the upper edge of the sternal notch, this level is a foveal tissue gap, the blood vessels are microscopic and few, and the flap is separated without bleeding after the electric knife. After the flap is divided and fixed with upper and lower sutures, the flap is incised along the white line of the neck and separated from the two sides of the strap muscles, the pre-tracheal fascia (equivalent to the thyroid pseudo-peritoneum) is incised and separated in the gap between the true and false thyroid peritoneum, and the strap muscles are pulled from the superficial side of the true thyroid peritoneum to the lateral side to reveal the front of the thyroid gland and the internal jugular vein located on the lateral side of the thyroid gland. For large tumors, the lateral approach of the strap muscle can be used. The thyroid lobe is carefully palpated and visualized in order to understand the pathological symptoms that cannot be revealed by the preoperative examination. By bluntly separating the cricothyroid space, the cricothyroid muscle is visible and the superior thyroid pole is retracted laterally. To avoid damage to the external branches of the superior laryngeal nerve, the branches of the superior thyroid artery and vein should be separated and ligated one by one close to the thyroid envelope. The posterior branches of the superior thyroid artery should not be ligated as much as possible to protect the blood supply to the superior thyroid parathyroid gland. This is known as the “superior thyroid decapitation technique”. This naturally preserves the superior parathyroid glands. Until the superior thyroid pole is sufficiently free, the thyroid cone, if present, should be completely detached at this time, and the isthmus can be detached through an approach from the subcricoid surface of the trachea. After the upper pole of the thyroid is sufficiently free, we begin to separate and ligate the inferior thyroid veins and arteries entering the thyroid gland one by one. The key at this point is to deal with the tertiary vascular branches located in the peritoneum, gradually ligating and separating them and gradually working backwards to the inferior thyroid artery and the area of the laryngeal nerve. The lateral lobe of the thyroid gland is freed with a smooth true peritoneum, and the laryngeal nerve and branches of the inferior thyroid artery can be seen near the posterior border of the lateral lobe of the thyroid gland. By performing thyroid dissection in this manner, the laryngeal nerve and parathyroid glands are protected from damage. After both the superior and inferior thyroid glands are free, the entire lateral lobe of the thyroid gland is turned inward, and the medial side of the lateral lobe of the thyroid gland and the isthmus are separated from the trachea while the lateral ligament of the thyroid gland is cut at the same time, while the medial side of the laryngeal nerve may bleed. When the thyroid gland is separated to the contralateral trachea, the thyroid gland is broken and the stump is interrupted with mattress sutures to stop bleeding, and the stitches should be crossed. The operation is completed after lobectomy, saline cleaning of the wound, complete hemostasis of the operative cavity, placement of negative pressure drainage tube, and then suturing of the skin [3]. The difficulties in surgery Thyroid surgery is a kind of delicate surgery, and the difficulties in surgery are generally in the following three aspects: first, the identification and protection of the recurrent laryngeal nerve, second, the identification and protection of the superior laryngeal nerve, and third, the identification and preservation of the parathyroid gland. This requires skillful head and neck surgery and a good knowledge of neck anatomy. 3.1 Identification and protection of the recurrent laryngeal nerve Identification and protection of the recurrent laryngeal nerve is critical in thyroid surgery. It is well established that finding the recurrent laryngeal nerve rather than avoiding it is the safest way not to damage the recurrent laryngeal nerve in thyroid surgery. The ideal method and anatomic landmarks for identifying the recurrent laryngeal nerve have always been controversial. The traditional surgical approach of finding the recurrent laryngeal nerve in the tracheoesophageal groove does not appear to be very effective because the surgical dissection is different from the cadaveric dissection, and the surgical dissection often deviates the recurrent laryngeal nerve from the tracheoesophageal groove or the tracheoesophageal groove is not visible or disappears under the strain. Some scholars also advocate finding the inferior thyroid artery first and then the inferior end of the recurrent laryngeal nerve, but because of the large amount of variability in nerve and vessel anatomy, it can sometimes be difficult to find the recurrent laryngeal nerve with this approach. Our experience is to locate the distal laryngeal nerve near the cricothyroid joint and then follow the course of the laryngeal nerve to find the proximal laryngeal nerve, because the entry point of the laryngeal nerve is constant at the cricothyroid joint. If the nerve cannot be fully dissected, it should be identified by its direction and the course of the longitudinal nerve. At this time, the descending branch of the hypoglossal nerve and the anastomosing branch of the sympathetic nerve and the recurrent laryngeal nerve should be identified, so that they are not mistaken for the non-recurrent laryngeal nerve. The laryngeal nerve that has not yet been discovered. The laryngeal nerve should be dissected close to the side of the thyroid envelope when seen, rather than deliberately exposing it, so that the nerve is theoretically covered and protected by a layer of fascia, which minimizes damage to the blood supply. Adequate hemostasis can be ensured by using an electric knife to stop the bleeding point on the trachea away from the area of the recurrent laryngeal nerve. Bipolar electrocoagulation can be used to treat small portions of tissue adjacent to the recurrent laryngeal nerve. It is safe to suture the troublesome bleeding point in the Berry ligament area using a small vessel suture. If the nerve is not found, please note the following: 1) the laryngeal nerve does not return; 2) the nerve is encapsulated by an extraglandular lesion of thyroid cancer; 3) a large Zuckerkandl node makes the laryngeal nerve look like it has entered the gland; 4) anatomical variations are more on the right side than on the left. 3.1.1 Identification of anastomosing branches of the sympathetic nerve and RLN There is an occasional direct connection between the cervical sympathetic ganglion and the recurrent laryngeal nerve (anastomosing branch of the sympathetic nerve and RLN, SILAB), and it is now recognized that there are many direct anastomosing branches between the sympathetic ganglion and the recurrent laryngeal nerve and between the lateral branch of the superior laryngeal nerve (EBSLN), and it has been reported that there are more than 2 SILABs thicker than the recurrent laryngeal nerve and mistaken for The non-returning recurrent laryngeal nerve has been reported to be thicker than 2 and mistaken for the non-returning recurrent laryngeal nerve, putting the true recurrent laryngeal nerve at risk of being cut. Intraoperatively, if there is any doubt about the origin of the apparent anastomotic branch, it should be traced back laterally. The non-returning laryngeal recurrent nerve is derived from the vagus nerve, however SILAB often originates from the middle cervical sympathetic ganglion or occasionally from the superior or inferior cervical sympathetic ganglion. Occasionally, the sympathetic trunk originates from the superior cervical ganglion, accompanying the EBSLN, and is intertwined with the laryngeal return nerve via a more distal branch along the Galen nerve, although this nerve itself is thought to contain primary receptors and some motor fibers. Branches may also leave the RLN and enter directly into the thyroid parenchyma, and to avoid severing any of the small, true superior branches of the laryngeal recurrent nerve, any such branch that looks like it is going into the thyroid parenchyma should be carefully examined. This is important in identifying the presence of anastomotic branches of the sympathetic nerve during thyroidectomy. 3.2 Routine identification of the lateral branch of the superior laryngeal nerve (EBSLN) The lateral branch of the superior laryngeal nerve (EBSLN) was once known as a neglected nerve for thyroid surgery, and most surgeons simply believed that nerve injury could be prevented by avoiding exposure of the nerve. However, it is now recognized that injury to the EBSLN is relatively common and there is also the potential to cause potentially significant injury, especially to those patients who work by voice such as announcers. The approach in our unit has been to try to find the nerve, although this has previously been done in only 60 patients. Recently Aina and Hisham concluded that the EBSLN can be routinely found in patients above 90, a level that has reached a new baseline in the field of endocrine surgery. The authors concluded that the key to finding this nerve is to look for it in the avascular plane between the medial edge of the superior pole of the thyroid and the cricothyroid muscle, by having the lobe retract laterally to facilitate this operation. If the nerve is to be identified and preserved, vigilance for variation in the location of the EBSLN according to the CERNEA classification is mandatory. type 1: the location of the EBSLN in relation to the thyroid gland is quite clear, with direct access to the cricothyroid muscle more than 1 cm above the superior thyroid pole. type 2a: when the nerves enter the parenchyma of the glandular lobe, they pass through the adjacent area of the superior thyroid pole vessels. type 2b: the nerve passes through the thyroid gland lobe anterior surface. It is important to be alert to anatomical variations when avoiding injury to the nerves, such as the Galen nerve, which is the direct link between the RLN and the EBSLN. Zuckerkandl’s nodule was first proposed by Zuckerkandl in 1902, and this structure is a special anatomical structure. According to the method described by pelizzo, it can be graded from 0 to 3 depending on its size. It is a source of localized pressure symptoms, especially when the thyroid itself is relatively small. Also, the importance of the Zuckerkandl nodule is that it can be a source of persistent, unrelieved compression symptoms or recurrence if not sought and removed during surgery. Understanding the anatomy of the Zuckerkandl node is central to safe surgical excision of the thyroid gland, which is usually enlarged laterally to the point where the recurrent laryngeal nerve appears to enter the thyroid parenchyma through its lateral fissure, a location that some surgeons commonly describe as the nerve entering the thyroid parenchyma. Even if the recurrent laryngeal nerve is not first evident, the earlier stereotypic position of the Zuckerkandle node usually makes the RLN easy and safe to dissect. However, an uncommon, but highly dangerous location is where the RLN enters laterally into a enlarged Zuckerkandl node, placing the RLN at a higher risk of injury during dissection of this node. Another important aspect is that the normal superior parathyroid glands originate from the fourth gill slit, which is often closely associated with the Zuckerkandl nodule. 3.4 Identification and preservation of the parathyroid glands For many years, the basic principle of preserving the parathyroid glands in thyroid surgery has been to preserve all vascular branches of the parathyroid glands in situ. In addition, it is generally accepted that apparently preserved parathyroid glands should be maintained in tan color, which is easy to identify and can thus be preserved intact. In over 3000 procedures performed by the authors, not a single patient with permanent hypoparathyroidism has been identified. The incidence of temporary hypoparathyroidism is extremely low (0.4). This may be due to an unrecognizable or delayed local ischemia of the preserved parathyroid tissue. It is now recognized that not only is dissection of an ultimately vascular parathyroid gland a rather time-consuming procedure, especially when the parathyroid gland is located high on the thyroid surface, but it is not necessary to preserve the parathyroid gland. In many cases, the parathyroid gland is painstakingly dissected over each vessel terminus, only to have the vessel embolize shortly thereafter, either because of thrombosis of the slender blood supply vessels or because of swelling and edema of the gland during dissection of the envelope. In individual patients, the absence of terminal vessels allows these parathyroid glands to be fixed higher up on the lateral surface of the thyroid gland, making it difficult to dissect the terminal vessels. Or the terminal vessels may have been damaged. If there is any intraoperative doubt about the survival of the parathyroid gland, it can be removed, cut into 1 mm squares, and transplanted near the sternocleidomastoid muscle.