Fig. 5.1
Preoperative photograph demonstrating both a healed mini-incision at 3 weeks on the left and matching skin crease 2.5-cm mini-incision placement on the right in a patient undergoing completion thyroidectomy for follicular cancer (From Palazzo FF, et al. Safety and feasibility of thyroid lobectomy via a lateral 2.5-cm incision with a cohort comparison of the first 50 cases: evolution of a surgical approach. Langenbecks Arch Surg. 2005;390:230–5; with permission)
MITS and Toxic Nodules
Solitary autonomous or toxic nodules are ideally suited to a MITS procedure. The principle aim of surgery (as distinct from the use of radioiodine ablation for toxic nodules) is to maximise preservation of normal thyroid tissue and avoid long-term hypothyroidism. Radioiodine has a significant risk of inducing long-term hypothyroidism, while thyroid lobectomy has reported rates of postoperative hypothyroidism between 15 and 35 %. This risk is even lower with MITS because only part of the thyroid lobe containing the toxic nodule is excised.
Surgical Technique of MITS
The Central Mini-incision Approach for Thyroid Lobectomy
Minimal invasive thyroidectomy with a central mini-incision is a technique that is performed through a small central incision, usually 3 cm or less. This is placed higher in the neck compared to the classic Kocher collar incision, usually directly over the cricoid. The surgeon needs to have a headlamp, as good illumination is critical, and usually magnified glasses. Because of the higher incision location, it is not necessary to develop large subcutaneous flaps, making this approach well suited for the use of local regional anaesthesia. A direct ligation of the superior pole vessels can be performed as a first step, as the incision is situated in the skin crease close to the cricoid cartilage. This procedure is best undertaken as a sutureless technique, using either electrothermal or ultrasonic energy devices for vessel ligation. Finally, the target lobe can be removed through the minimal incision by pulling it in a superior-medial direction, as the superior pole of the thyroid is usually more rigid and fixed than the mobile inferior pole. At this stage the opportunity arises to identify the recurrent laryngeal nerve (RLN). To improve exposure and allow identification of the key anatomical structures, the incision must be moved around the operative field and maintained in precise position with retractors.
The Lateral Mini-incision Approach
The major concern with the central mini-incision approach is the limited view of the lateral structures, in particular the RLN, especially if it is in an anatomically challenging relationship with the inferior thyroid artery or passes medial to an enlarged tubercle of Zuckerkandl. For this reason we prefer the lateral mini-incision approach for MITS procedures, providing, as it does, direct visualisation of the entire lateral anatomy related to the thyroid gland, including the RLN and the parathyroid glands. Concurrently it provides the cosmetic advantages of a laterally placed, high skin crease incision.
For the lateral approach general anaesthesia is used and the patient is placed in the supine position with the neck held in mild extension. A headlight is used to provide appropriate illumination of the operative field within the mini-incision. The procedure starts with a 2.5-cm lateral transverse incision made in a skin crease near the level of the thyroid nodule, directly over the medial border of the sternocleidomastoid (SCM) muscle. The sub-platysmal plane can be developed digitally to be able to fully use the mobility of the skin incision and move it over the relevant anatomy during the procedure. After the medial margin of the SCM is exposed together with the lateral border of the strap muscles, the SCM is retracted laterally and the space posterolateral to the strap muscles is developed to reveal the lateral border of the thyroid gland. This is then retracted medially to enable division of the middle thyroid vein. The space medial to the common carotid artery is then dissected down to the prevertebral fascial plane.
Superior Pole Dissection
The upper aspect of the dissection is achieved by moving the surgical field in the cranial direction and gently pulling the upper thyroid pole laterally to open up the avascular plane between the medial border of the upper pole and the cricothyroid muscle. In this way the external branch of the superior laryngeal nerve can be visualised and preserved. The superior thyroid artery is then divided (Fig. 5.2).
Fig. 5.2
Exposure and dissection of the superior pole achieved by retraction of the wound superiorly (From Palazzo FF, et al. Safety and feasibility of thyroid lobectomy via a lateral 2.5-cm incision with a cohort comparison of the first 50 cases: evolution of a surgical approach. Langenbecks Arch Surg. 2005;390:230–5; with permission)
Trachea and Isthmus
The skin incision is now repositioned to the midline to expose the trachea and to allow division of the isthmus. This results in increased mobility of the thyroid gland and permits the lateral dissection to be completed. It must be emphasised that routine division of the isthmus at this stage is a vital manoeuvre, in order to provide sufficient mobility of the thyroid lobe to enable it to be subsequently delivered through the mini-incision for the final stage of dissection (Fig. 5.3).
Fig. 5.3
Exposure and dissection of the isthmus achieved by retraction of the wound medially (From Palazzo FF, et al. Safety and feasibility of thyroid lobectomy via a lateral 2.5-cm incision with a cohort comparison of the first 50 cases: evolution of a surgical approach. Langenbecks Arch Surg. 2005;390:230–5; with permission)
Lower Pole Dissection
The skin incision is now moved caudally to facilitate mobilisation of the lower pole of the thyroid gland and to undertake a capsular dissection. At this stage it is important to identify and preserve the inferior parathyroid gland. If the parathyroid gland cannot be preserved on a vascularised pedicle, it is autotransplanted by injection into the adjacent SCM muscle (Fig. 5.4).
Fig. 5.4
Capsular dissection of the inferior pole of the thyroid achieved by retraction of the wound inferiorly (From Palazzo FF, et al. Safety and feasibility of thyroid lobectomy via a lateral 2.5-cm incision with a cohort comparison of the first 50 cases: evolution of a surgical approach. Langenbecks Arch Surg. 2005;390:230–5; with permission)
Lateral Dissection
The last step is to return the skin incision to its initial lateral position to enable delivery of the thyroid lobe, thereby improving the exposure of lateral gland (Figs. 5.5 and 5.6). This is performed, as with any open thyroid procedure, with capsular dissection encountering the recurrent laryngeal nerve as it passes medial to the tubercle of Zuckerkandl. At this stage the superior parathyroid is preserved if possible on a vascularised pedicle, or else autotransplanted. Finally, from the medial side, the ligament of Berry is progressively divided allowing the entire thyroid lobe to be delivered through the mini-incision. The entire lobe can then be removed at this stage if the location of the nodule requires a lobectomy. Once haemostasis has been confirmed, the skin incision is closed with subcutaneous absorbable sutures.
Fig. 5.5
The lateral aspect of the thyroid can be dissected after delivering the lobe through the mini-incision (From Palazzo, FF et al. Safety and feasibility of thyroid lobectomy via a lateral 2.5-cm incision with a cohort comparison of the first 50 cases: evolution of a surgical approach. Langenbecks Arch Surg. 2005;390:230–5; with permission)
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