7 Technique of Thyroidectomy

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7.1 Introduction

Thyroidectomy is the most frequent intervention in endocrine surgery. When performed in specialized centers, the operation is safe with low morbidity and a virtually 0% mortality [1]. Complications of thyroid surgery are directly correlated to the extent of resection and inversely proportional to the experience of the operating surgeon [1–4]. Thus, the cornerstones of safe and effective thyroid surgery are an adequate training, the understanding of the anatomy and pa- thology, as well as a meticulous dissection technique.

The dissection must be based on a sound knowledge of three-dimensional topographic anatomy, typical landmarks, and possible anatomic variations. The meticulous dissection technique is achieved by a proper exposure of all fine anatomic structures in a bloodless dry surgical field. The use of magnifying glasses (magnification 2.5–3.5 ×), bipolar coagulation, and fine titan clips or ligatures is highly recommended.

Neuromonitoring has proved useful for identifying the recurrent laryngeal nerve (RLN), in particular if

the anatomic situation is complicated by prior surgery [5]. However, neuromonitoring does not reliably predict postoperative outcome [6,7]. A recent study based on 288 patients undergoing thyroid surgery with intraoperative identification and intraoperative neuromonitoring showed that the incidence of recurrent nerve lesions in benign, malignant, and recurrent thyroid disease was not lowered by the use of intraoperative neuromonitoring [8]. Although an intact nerve function can be verified by this method, we do not recommend the routine use of RLN neuromonitoring.

The endocrine surgeon’s success depends completely on his or her devotion to a stepwise meticulous and fine dissection technique. Several dissection devices have recently been propagated for thyroid surgery. The harmonic scalpel using ultrasonic frictional heating to seal vessels is widely used in laparoscopic and open abdominal surgery. It is documented to be safe and fast for cutting and coagulating tissue. Its use for dissection during thyroidectomy has been evalu- ated in several studies and has been compared to the conventional clamp-and-tie technique. Two randomized studies [9,10] and two case-controlled studies [11,12] have shown that the harmonic scalpel significantly shortens the operative time compared to the conventional technique. This reduction of up to 20%

in operative time has proved to be cost-effective [13].

Thyroidectomy using the electrothermal seal- ing technique has also been introduced and tested [14,15]. However, this technique did not significantly reduce operative time, blood loss, or the complica- tion rate compared to conventional knot-tying but it increased operative costs in one study [15]. All men- tioned studies compared new ultrasonic or diathermy dissection devices with the conventional clamp-and- tie technique. However, no comparison with the utilization of hemoclips to secure smaller vessels was done. Personally, I make liberal use of hemoclips for thyroid and parathyroid surgery and I am convinced that this speeds up the operation similarly to the use of the quite costly new devices.

7 Technique of Thyroidectomy

Daniel Oertli

Contents

7.1 Introduction . . . 81

7.2 Extent of Surgery and Definitions . . . 82 7.3 Preoperative Measures . . . 82

7.4 Positioning and Draping . . . 82 7.5 Surgical Steps . . . 82

7.5.1 Skin Incision and Creation of Skin Flaps . . . 82 7.5.2 Strap Muscles . . . 83

7.5.3 Upper Pole . . . 83

7.5.4 Isthmus and Pyramidal Lobe . . . 84 7.5.5 Hilum of the Gland . . . 84

7.5.6 Handling of the Parathyroid Glands . . . 85 7.5.7 Lower Thyroid Pole . . . 86

7.5.8 Removal of the Lobe . . . 86 7.5.9 Wound Closure . . . 86

7.6 Reoperative Thyroid Surgery . . . 86 7.7 Minimally Invasive Thyroidectomy . . . 87

References . . . 87

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7.2 Extent of Surgery and Definitions

Until 2000 there was no uniformly applied definition in the literature regarding the extent of thyroidectomy that should be performed for benign and malignant pathologies. To fill this gap, Kebebew and Clark formulated such a classification (Table 7.1) [16].

Lumpectomy or nodulectomy refer to removal of a thyroid nodule alone with minimal surrounding thyroid tissue. Partial thyroidectomy involves removal of a nodule with a larger margin of normal thyroid tissue. The definition of subtotal thyroidectomy belongs to the bilateral removal of more than 50% of each lobe including the isthmus. Lobectomy or hemithyroidectomy refers to the complete removal of one lobe with the isthmus. Near total thyroidectomy is defined as the total extracapsular removal of one lobe including the isthmus with less than 10% of the contralateral lobe left behind. During total thyroidectomy both lobes and the isthmus are completely removed leaving behind only viable parathyroid glands.

7.3 Preoperative Measures

All patients should be rendered euthyroid before surgery. Preoperative preparation of patients with thyro- toxicosis is particularly critical to avoid operative or postoperative thyroid storm. The planned procedure should be discussed with the patient and informed consent must be obtained. Routine preoperative laryngoscopy is not necessary if the patient does not report voice changes [17]. However, if patients have previously undergone any type of neck surgery or if the voice appears to be altered, laryngoscopy is indicated.

The tentative skin incision is marked preoperatively using a permanent marker pen on the awake patient with reclined neck. This is done in a symmetric fashion along the Langer’s skin lines or in a skin crease in

between the medial borders of the sternocleidomastoid muscles. The appropriate position of the neck incision is approximately two finger breadths above the sternal notch or in the middle between the sternal notch and the thyroid cartilage. If the incision is too low, the tendency to keloid formation and resulting unsatisfactory cosmesis is increased.

7.4 Positioning and Draping

The patient is positioned with the neck extended.

Rolled towels are placed under the shoulders which allow sufficient neck extension. A sponge doughnut is placed under the occiput for adequate head support.

In order to prevent venous congestion in the neck, the head of the table is elevated to a 30° position during surgery. Disinfection is performed using an alcoholic agent without iodine which might interfere with postoperative radionuclear scanning and ablative therapy.

The surgical field is draped from below the sternal notch up to the chin and on the posterior margin of the sternocleidomastoid muscles.

7.5 Surgical Steps

Every surgeon should adopt a stepwise, standardized strategy for thyroidectomy. One possible way (the author’s recommendation) for a successful thyroidectomy is presented below. Modifications may be necessary in the case of perithyroidal inflammation, large goiters, or unexpected intraoperative findings.

7.5.1 Skin Incision and Creation of Skin Flaps

A curvilinear collar-type incision is placed trans- versally along the Langer’s line of the skin, i.e., the

Table 7.1 Definition of extent of resection

Thyroidectomy procedure Removal of: Indications

Partial (nodulectomy, lumpectomy) Nodule + margin of normal tissue Benign lesion

Subtotal More than one half of the thyroid gland

and isthmus

Benign lesion

Lobectomy (= hemithyroidectomy) One entire lobe and isthmus Standard initial treatment for all indeter- minate nodules

Near-total Lobectomy on one side, isthmectomy and

subtotal resection of contralateral lobe

Papillary carcinoma in a low-risk patient, not requiring radioiodine ablation

Total Both lobes and isthmus Any other type of thyroid carcinoma

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standard Kocher’s incision. The use of a natural skin crease if present seems attractive. In order to optimize cosmesis, the skin incision should be as long as necessary but as short as possible. Personally, the author believes that a 4- to 5-cm incision allows safe thyroidectomy in most cases and results in excellent cosmesis. However, patients with larger tumors or goiters or those with short necks will require a larger incision for optimal exposure. The incision is carried out through the skin and the subcutaneous layer through the platysma muscle to the lateral extent of the skin incision. The two skin flaps are created by dissect- ing them away from the strap muscles upward to the thyroid cartilage and downward to the sternal border.

Elevation of the two flaps is almost bloodless if the layer beneath the platysma is followed and dissected.

The cranial flap is transfixed using stay sutures that are secured on two hooks placed on a horizontal rod which is placed above the patient’s head (Fig. 7.1). The caudal flap is pulled downward using a Roux retractor enabling optimal exposure to the strap muscles.

7.5.2 Strap Muscles

The approach to the thyroid capsule is done by split- ting the strap muscles in the midline. Small crossing vessels are treated with bipolar coagulation. For a bilateral approach, the left thyroid lobe is first dissected.

This is usually the more cumbersome preparation

when the operating surgeon is positioned on the right side of the patient. By predominantly blunt dissection, the anterior aspect of the respective thyroid gland is exposed. Caution should be applied while retracting the strap muscles to avoid disrupting the medial thyroid veins. These veins are isolated and either ligated or clipped and divided. Proper exposure to the lateral aspects of the thyroid gland is achieved using right- angled (de Quervain) retractors. Division of the strap muscles may be necessary in the case of a very large goiter, when a central neck dissection is indicated, or in reoperative cases. The two muscles (sternohyoid and sternothyroid) are separated using diathermia.

Their borders are secured with 2-0 threads that serve as stay sutures.

7.5.3 Upper Pole

Using Kocher’s forceps, lateral retraction of the upper pole of the thyroid lobe is applied in order to open up the avascular space [18] between the lobe and the cricothyroid muscle, thus exposing the external branch of the superior laryngeal nerve [19,20]. This nerve can sometimes be identified as it descends with the vessels and anterior to the cricoid muscle but is often not visible (Fig. 7.2). A recent study showed that the identification and dissection of the superior laryngeal nerve do not lower the risk of damage compared with the simple transection of the superior vein and ar-

Fig. 7.1 Intraoperative situation after creation of the superior skin-platysma flap which is secured with threads. The inferior flap is retracted using a Roux retractor

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tery close to the thyroid [21]. The superior vessels are usually ligated with transfixing sutures. Large goiters with prominent superior poles often require more than one transection step.

7.5.4 Isthmus and Pyramidal Lobe

By blunt dissection, the isthmus is freed from the underlying trachea and divided between transfixing ligatures. If subtotal or total thyroidectomy is performed, the division of the isthmus is often not necessary. The pyramidal lobe, which originates more often from the left thyroid lobe, is traced upward and removed as completely as possible.

7.5.5 Hilum of the Gland

Only the complete division of the superior vessels enables the surgeon to medially rotate and anteriorly mobilize the gland which results in optimal exposure of the hilar structures. Capsular dissection, as described by Thompson et al. [22], refers to the development of a plane between the thyroid capsule and the tertiary branches of the inferior thyroid artery. The branches are ligated or clipped individually directly on the surface of the thyroid gland. This method, which is widely practiced today, minimizes surgical damage to both the parathyroid glands and the RLN [23]. Me- ticulous dissection steps will then enable identification of the RLN where it crosses the inferior thyroid artery, as well as the two parathyroid glands. It is wise to preserve as much of the inferior thyroid artery and its branches as possible, since it supplies the blood to the two parathyroid glands. Truncal ligation of the inferior thyroid artery should be omitted. However, it is sometimes helpful to hold the trunk of the artery

using a vessel loop in order to facilitate further exposure of the RLN. The nerve may easily be found at its constant landmark, the so-called Zuckerkandl tuberculum [24,25], where it crosses beneath the thyroid gland and enters below Berry’s ligament of the thyroid cartilage (Fig. 7.3). The RLN can always be identified laterodorsally to the ligament of Berry; it never penetrates the ligament [26]. The left RLN leaves the vagus nerve as the vagus crosses over the arch of the aorta. It hooks around the aorta and ascends again, similarly to the right RLN, laterally to the trachea to its terminal branches within the laryngeal muscles.

This explains why the left RLN runs closer to the tra- cheoesophageal groove than the right RLN [27]. The RLN may pass posteriorly or superficially to the inferior thyroid artery or its branches intertwine with many variations. Although several methods of local- izing the RLN have been described, surgeons should be aware of the variations and must have a thorough knowledge of the normal anatomy to achieve a high standard of care. This will ensure the integrity and safety of the RLN during thyroid surgery. The identification of the RLN may be assisted by palpation; it may be felt like a cord that can be rolled against the trachea [28]. The nerve appears as a white cord com- monly accompanied by a small artery. To clearly iden- tify the RLN, dissection of its crossing point with the inferior thyroid artery is critical. Gentle dissection, best performed with a fine curved jaw hemostat, is necessary at this point. Although there are many dif- ferent anatomic relationships between the nerve and the artery, the crossing point is one constant anatomic landmark where the RLN can usually be identified.

One exception to this rule is the non-recurrent inferior laryngeal nerve (Fig. 7.4). This anomaly is found virtually only on the right side and is associated with an anomalous right subclavian artery with a reported frequency of 0.2–0.8% [29–31].

Fig. 7.2 Lateral and caudal retraction of the upper pole of the thyroid in order to open up the avascular space between the lobe and the cricothyroid muscle, thus exposing the external branch of the superior laryngeal nerve

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7.5.6 Handling of the Parathyroid Glands

Regardless of whether a unilateral lobectomy or total thyroidectomy is performed, all identified parathyroid tissue should be preserved on its native blood supply. If a gland is devascularized during dissection, it should be transplanted. Although there have been sporadic reports of parathyroid autotransplantation, it has only been in the last 30 years that the technique has become used and only recently has it become ac- cepted as part of routine clinical practice during total thyroidectomy [32]. The best way to preserve the parathyroid glands in situ is the extracapsular dissection of the thyroid gland. With the utilization of the extracapsular dissection, the parathyroid glands are swept off the thyroid capsule and are left in situ with their vascular pedicles. The superior parathyroid gland is usually found after mobilization of the superior pole of the thyroid. The lateral aspect of the thyroid gland superior to the inferior thyroid artery usually reveals a fat pad where the parathyroid can be found. This fat pad including the parathyroid gland should be mobilized off the lateral aspect of the thyroid starting at its superior medial edge and sweeping the pad inferiorly and laterally. It is important not to disrupt the fat pad

and not to dissect the gland further than just beyond the edge of the thyroid to preserve its blood supply.

The inferior parathyroid gland is usually found at the inferior pole of the thyroid or within the tongue of the thymus. Once identified, it is taken off the inferior pole in a similar fashion to the superior gland.

Disruption of the thyroid-thymic ligament should be avoided as it provides most of the blood supply to the inferior parathyroid gland.

All normal but devascularized parathyroid tissue should be transplanted into the sternocleidomastoid muscle or other convenient muscle at the time of thyroidectomy. Sometimes, the gland is partly devascularized and should then be trimmed back to the area of good arterial flow and viability. The remaining portion is removed, minced, and autotransplanted.

Histologic confirmation of parathyroid tissue is cru- cial in the setting of thyroid cancer. Nodal metasta- ses from thyroid cancer can mimic parathyroid tissue and should not be transplanted. There are principally two ways to do a parathyroid autotransplantation.

First, the gland tissue is removed and minced into tiny cubes that are smaller than 1 mm3. By separating the muscle fibers of the sternocleidomastoid muscle, a pocket containing about a 1-ml space is created using

Fig. 7.3 Topographic relationship between the inferior thyroid artery and the tubercle of Zuckerkandl to the recurrent laryngeal nerve and the superior parathyroid gland

Fig. 7.4 Intraoperative finding of a non-recurrent inferior laryngeal nerve

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blunt dissection. The minced tissue is then transplanted into the pocket which is closed and marked by hemostatic clips or a non-absorbable thread. It is essential to leave a completely dry pocket behind since hematoma formation within the pocket would be prone to phagocytosis including the parathyroid tissue. The second possibility to achieve the parathyroid transplantation is the creation of a parathyroid suspension using saline which is then aspirated with a 2-ml syringe and injected into the sternocleidomastoid muscle with an 18-gauge needle.

7.5.7 Lower Thyroid Pole

The transection of the vessels running to the lower pole is usually done after proper exposition of the RLN. Veins from the anterior superior mediastinum are exposed and divided very close to the thyroid gland. In up to 12% of cases an accessory ima artery may spread into the lower pole. This vessel may origi- nate either from the brachiocephalic trunk, the right carotid artery, directly from the aortic arch, the inter- nal thoracic artery, or from a mediastinal artery. This vessel may cause intraoperative bleeding especially when a large retrosternal goiter is bluntly mobilized.

7.5.8 Removal of the Lobe

During the final steps of the thyroidectomy, the lobe is dissected away from the trachea under constant exposure and preservation of the RLN. The dense attachments at the level of the posterior suspensory ligament (Berry) usually require sharp dissection. At- tention must then be paid to the relatively constant superior branch of the inferior thyroid artery (crimi- nal branch) that often crosses underneath the RLN and spreads medially from beneath the nerve into the

thyroid gland. This small artery should be isolated and clipped before cutting (Fig. 7.5). The use of any cautery or other thermal dissection device should be avoided at this step due to the potential for thermal injury of the RLN that is in close proximity to the inferior thyroid artery. Inadvertent bleeding from this artery and uncontrolled attempts of hemostasis at this point of dissection may harm the RLN. Sudden bleeding is best handled, with the aid of suction, by identifying the vessel stump, and clamping or clipping, being constantly aware of the presence of the RLN. If oozing occurs at this point, the placement of a hemo- styptic gelatine sponge is advised.

7.5.9 Wound Closure

A postoperative drain can never replace accurate hemostasis and is of little or no use if severe postoperative bleeding occurs. Two randomized trials did not show any advantage of drainage after thyroidectomy [33,34]. The strap muscles are sutured continuously with a 3-0 absorbable thread, the platysma with a 4-0 thread, and the skin is closed by an intradermal running suture using 5-0 absorbable thread. A smooth collar may be used for the first 24 hours postopera- tively and the patient should be advised to keep a head up position of about 30° in order to minimize venous congestion and swelling of the soft tissues around the wound.

7.6 Reoperative Thyroid Surgery

Avoidance of RLN injury is best achieved by identification of the nerve early during reoperation. The best approach is the identification of the RLN in a previously undissected area and to follow the nerve into the dissected scarred region (“from the known

Fig. 7.5 Last steps of dissection for thyroid lobec- tomy: a small superior branch of the inferior thyroid artery usually crosses underneath the RLN and spreads medially from beneath the nerve into the thyroid parenchyma

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toward the unknown”). Although the use of intraoperative neuromonitoring for confirmation of the RLN has some theoretical applications for a difficult dissection, visual identification of the RLN is still essential. Principally three distinct approaches exist for reoperative thyroid and parathyroid surgery.

First, the lateral or “back door” approach enters the thyroid bed between the anterior border of sternocleidomastoid and the strap muscles (Fig. 7.6). Lat- eral mobilizing of the sternocleidomastoid muscle exposes the sternohyoid and underlying sternothyroid muscles, whose fibers spread out inferiorly and laterally over the carotid artery and jugular vein. Gentle retraction of the carotid artery exposes the paratracheal soft tissue. This area, which is located inferolat- erally to the inferior pole of the thyroid, is, if present, usually unchanged from previous interventions. Here, the RLN can usually be identified without difficulty.

Second, the low anterior approach enters the thyroid bed similarly to the primary operation. The strap muscles are separated in the midline down to the sternal notch and are reflected laterally. The dissection is then carried out in the paratracheal regions inferior to the area of previous dissection where the right or left RLN is identified.

Third, the anterior superior approach exposes the region between the superior pole of the thyroid, if present, and the larynx. The RLN can be identified as it enters the larynx with dissection in this avascular space between the superior thyroid pole and the larynx. This can even be realized without taking down the superior pole vessels. The RLN can be traced inferiorly and identified in the hilum of the thyroid which is often extensively scarred.

7.7 Minimally Invasive Thyroidectomy

Whereas minimally invasive parathyroidectomy has become popular among endocrine surgeons, experience with minimally invasive thyroidectomy remains limited. The feasibility and safety of fully endoscopic thyroidectomy or video-endoscopically assisted thyroidectomy have been proved in a few studies that reported a minor risk of complications and a low con- version rate of 3–11% [35–38]. The key to the success of these approaches is a rigorous selection of the patients. Inclusion criteria are solitary nodules smaller than or equal to 3 cm, thyroid volume less than 20 ml, absence of thyroiditis, absence of previous neck irra- diation, and absence of previous neck surgery. Thus, minimally invasive thyroidectomies are valid alterna- tives to conventional surgery for patients with small solitary nodules [39]. However, only 10.6% of patients requiring thyroid surgery eventually qualify for this approach [40].

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