Operative Technique of Endoscopic Thyroidectomy: A Narration of General Principles

Abstract

Endoscopic thyroidectomy is fast becoming a reality with increasing experience in endocrine surgery. Many techniques of minimally invasive video-assisted thyroidectomy through cervical and extra-cervical routes such as chest wall, transaxillary, trans-oral, post-auricular, trans-luminal approach have been attempted. At present anterior chest wall or trans-axillary routes are favourite extra-cervical routes. In this context, we describe our operative technique of endoscopic thyroidectomy through chest wall to highlight the surgical steps of practical importance.

Introduction

Endoscopic thyroidectomy (ET) has rapidly transformed from a fantasy into reality. Ever since the onset of laparoscopic era in early 1980s, minimal access surgery is occupying the major share of operation theater lists in most of the surgical disciplines. Increasing confidence and experience in laparoscopic surgical skills have permeated into endocrine surgery after demonstration of endoscopic parathyroidectomy and thyroidectomy in 1996 by Gagner [1]. In recent past, more centers are performing ET in increasing numbers, mostly in Western and affluent Asian countries [1–3]. Various techniques such as video-assisted, totally endoscopic, and gasless approaches have been performed [4]. To improve the cosmesis, extracervical access such as transaxillary (TA), chest wall (CW), and axillo-breast (AB) routes have been successfully employed. As applicable to any laparoscopic procedure, even ET requires adequate surgical experience and knowledge of surgical principles for its optimal performance. In this context, we present an overview of the operative technique of ET in the stepwise manner with specific emphasis on practical surgical steps irrespective of the access route.

Details of Surgical Technique

The operative technique is subdivided into 10 surgical steps in chronological order of surgery and each step is described in details:

1. Access, ports, and operative space creation: Surgical access can be broadly classified as cervical and extracervical routes. Within extracervical route, TA, CW, and AB approaches are more frequently practiced. It is still early days to comment on superiority of one technique over the other. Usually, a 10 mm camera port and two 5 mm working ports are used with an additional port optionally (Fig. 1).

Fig. 1.

Endoscopic thyroidectomy—port placements with triangulation over anterior chest wall

Irrespective of the access route, operative space (OS) has to be created in contrast to natural OS in abdomen or pleural cavity. We create OS through combination of blunt and sharp subcutaneous or subpectoral fascial dissection with long hemostats, balloon inflation, and diathermy dissection under vision (Fig. 2). This dissection is continued in subplatysmal plane of the neck beyond the clavicle. This latter dissection is done up to the level of thyroid cartilage and over the ipsilateral thyroid lobe.

• 2.Reaching thyroid gland in visceral space of neck: In ET, similar to open thyroidectomy, the thyroid goiter (TG) can be approached through midline between strap muscles or lateral approach between strap muscle and sternocleidomastoid (SCM) muscle. This lateral approach is especially useful in ET as it is an avascular plane, avoids anterior jugular veins, and aids in direct control of middle thyroid vein. With diathermy the deep fascia over this plane is incised and SCM is retracted. Lateral one-third of strap muscles can be cut for extra space. Middle thyroid vein is controlled with clips.
• 3.Mobilization of thyroid gland: Deep-to-deep cervical fascia, the avascular plane between thyroid lobe and carotid sheath, is further opened up till prevertebral fascia. Pretracheal fascia over the thyroid lobe is teased close to TG and it is rotated medially. This dissection continues till the lateral part of superior thyroid pedicle is visualized.
• 4.Control of superior thyroid pedicle: Strap muscle overlying the TG is retracted and if needed its lateral one-third is cut. Once superior pedicle blood vessels are visualized, they must be skeletonized, teasing away the pretracheal fascia and strap muscle fibers with bipolar diathermy. The skeletonized pedicle blood vessels are individually double clipped on proximal side and single clipped toward TG (Fig. 3). They are divided to devascularize TG superiorly.
• 5.Control of inferior thyroid pedicle: With the combination of blunt and sharp dissection assisted by diathermy, the trachea below the ipsilateral isthmolobar junction is visualized. The multiple inferior thyroid veins (ITVs) should be skeletonized from the medial to the lateral side. ITVs are individually clipped and divided (Fig. 4). Before dividing lateral most ITV, it is mandatory to differentiate it from recurrent laryngeal nerve (RLN) as it courses parallel to them. If in doubt, lateral ITV should be divided after demonstration of RLN only. However, with the endoscopic magnification, it is not as difficult to differentiate ITV from RLN as in open surgery.
• 6.Identification of recurrent laryngeal nerve (RLN): As ET is usually performed for smaller goiters, RLN lies in normal location in majority of cases. It courses in trachea-esophageal groove between the branches of ITA. With endoscopic magnification, RLN is seen very clearly as a white string-like structure with a vasa nervosum accompanying it, posterior to TG (Fig. 5). Low-amperage diathermy current is employed at least 2 mm away from RLN to divide vascular structures. RLN is followed up, until its entry at the lower border of inferior pharyngeal constrictor.
• 7.Parathyroid glands (PT): Thorough anatomical and embryological knowledge along with adequate experience in thyroid surgery is mandatory to identify PT. They should be looked for in usual anatomical locations. Superior PT, which is the most constant, is located posterosuperior to RLN in more than 80 % of individuals (Fig. 5). Capsular dissection close to the capsule of TG with meticulous hemostasis using bipolar diathermy is done to preserve PT. Inferior PT is located antero-inferior to RLN over the inferior pole of thyroid (Fig. 4), which is dissected and preserved similar to superior PT.
• 8.Ligament of Berry: Division of posterior suspensory ligament of thyroid also known as ligament of Berry is the penultimate step of ET. After identification of RLN over its entire course, the ligament of Berry is divided close to TG and away from RLN using bipolar diathermy, as it is a vascular structure (Fig. 5).
• 9.Separation of TG from thyroid bed: The only attachment of TG in neck after prior steps is flimsy, hypovascular areolar tissue between TG and tracheal perichondrium. It is dissected with sharp dissection using scissors after elevation of TG off the trachea.
• 10.Specimen extraction: Similar procedural steps are repeated on the contralateral side for total thyroidectomy. The thyroidectomy specimen is retrieved from the camera port under vision, after enlarging the incision by 1–2 cm. Placement of drain is optional after checking the thyroid bed for hemostasis.

Fig. 2.

Creation of operative working space in subplatysmal plane with diathermy

Fig. 3.

Intra-operative view of thyroid lobe (black arrow) and superior thyroid pedicle controlled with metallic clips (down arrow)

Fig. 4.

Intra-operative view showing inferior parathyroid (black arrow) and inferior thyroid pedicle (white arrow)

Fig. 5.

Intra-operative view showing superior parathyroid (down arrow) and recurrent laryngeal nerve (black arrow)

Discussion

There is need for general surgeons and practicing thyroid and endocrine surgeons to be aware of ET techniques and recent advances in the field. This is especially crucial in the scenario, wherein ET is likely to become a routine practice in future. It is feasible to perform ET for solitary thyroid nodule, Graves’ disease, multinodular goiter, low-risk differentiated thyroid cancer, central compartment neck dissections as demonstrated by many studies [1, 5, 6].

As women are predominantly affected with thyroid disease, endoscopic procedures with minimal or no scar in the neck are in demand. The ET techniques can be broadly divided into mini-incision minimally invasive, video-assisted gasless, and purely endoscopic with gas-insufflation methods [4]. According to anatomical access, ET can be performed through cervical, extracervical (chest wall, transaxillary), or combined approaches [7–9]. The obvious advantage of the extracervical approach is absence of visible scar in the neck and upper chest. The feasibility of the transaxillary approach has been demonstrated by many investigators, which further improves the cosmesis [10, 11]. Even novel access routes and methods such as postauricular approach [12], transoral approach [13], and robotic ET [14] have been reported.

All the ET techniques necessitate a subcutaneous or subpectoral working space creation, using internal or external maneuvers. External maneuvers for creation of space are special retractors with upward traction or skin hooks. The commonest internal maneuver is gas insufflation. Although various gases such as carbon dioxide, nitrogen, nitrous oxide, helium, air, krypton, and argon have been tested, CO₂ insufflation is proved to be the best option due to its high solubility, low cost, and noncombustibility [15]. But ET with gas insufflation is not without complications. It can be associated with hypercarbia, subcutaneous emphysema, and pneumomediastinum. Ochiai et al. used a long subcutaneous dissector to create a subcutaneous space, followed by low CO₂ insufflation pressure of 6 mm Hg to maintain it [16]. It is proposed to use lower CO₂ insufflation pressures of 4–6 mm Hg with intermittent desufflation to reduce gas-related morbidity [17].

Irrespective of different approaches for access, the operative steps around the thyroid gland are similar to open thyroidectomy. Thorough knowledge of thyroid surgical anatomy and extensive experience in standard thyroidectomy are mandatory to achieve optimal results with ET. Choice of laparoscopic instruments for dissection and hemostasis depends on surgeon’s experience. Although many studies have reported successful ET with various techniques, they are yet to be standardized. Technique of ET varies between individual or departmental or institutional practice. The proposed set of principles is a general overview of an ET technique for information, irrespective of approach and not a guideline for performing ET.