Important Triangles in Thyroid Surgery

Thyroidectomy is a surgical procedure involving removal of the thyroid glands. The procedure can be a hemi-thyroidectomy (partial removal) or can be a total thyroidectomy.

triangles in thyroidectomy
Triangles in thyroid surgery

The most important thing about thyroidectomy is the meticulous dissection needed for preserving the two nerves and bilateral parathyroid glands. These two nerves are the Recurrent laryngeal nerve (RLN) and External branch of superior laryngeal nerve (EBSLN).

Knowing the anatomy and landmarks in relation to thyroid helps in preservation of these vital structures during thyroidectomy. Classically multiple triangles are described for identification of these important nerves in thyroidectomy.

In this article we summarize these triangles in relation to thyroidectomy.

Beahrs Triangle or Riddle’s triangle

This is one of the most important triangle in relation with thyroid. This triangle is named after O H Beahrs. Its synonymous as Riddle’s triangle.

Baehr’s triangle is bounded by

  • common carotid artery as base,
  • inferior thyroid artery superiorly and
  • recurrent laryngeal nerve as the third side.

The triangle lies posterior to the thyroid gland, in the tracheo-esophageal groove.

Boundaries of Baehr’s triangle can be identified after retracting the ipsilateral thyroid lobe medially to safe guard the recurrent laryngeal nerve.

Simon's triangle

Classically, the RLN is identified intraoperatively in Simon’s triangle, which  is formed by

  • the common carotid artery laterally,
  • the oesophagus medially, and
  • the inferior thyroid artery superiorly.

The nerve  crosses the triangle.

Lore’s Triangle

This triangle described by Lore et al., is also for identification of recurrent laryngeal nerve.

  • Medial border of the triangle is formed by the trachea / esophagus,
  • the lateral border by carotid artery
  • and superior border by the surface of inferior pole of thyroid.

RLN triangle

This is an inverted triangle with

  • apex formed inferiorly by thoracic inlet,
  • trachea medially
  • the medial edge of retracted strap muscles as the lateral margin
  • the superior border is lower edge of the inferior pole of the gland

Recurrent laryngeal nerve exits as a single trunk here at thoracic inlet.

Joll's Triangle

Joll’s triangle is concerned with identification and preservation of External branch of superior laryngeal nerve (EBSLN).

  • The superior border is formed by superior attachment of strap muscles,
  • medial border by the midline and
  • lateral border formed by the upper pole of thyroid gland and superior thyroid vessels.

EBSLN lies in the floor of the triangle formed by the cricothyroid muscle. The triangle is also named as sternothyroid-laryngeal triangle.

Cricothyroid space of reeves

Reeve’s space is an avascular space between the upper pole of the thyroid gland and the cricothyroid muscle. Identification and opening up of the space is important for preservation of EBSLN.

The space opens up once the medial dissection is performed at the superior pole of thyroid gland. The ipsilateral thyroid lobe is given traction in a downward and outward direction to open up the sternothyroid—laryngeal triangle or “Jolls triangle”

Triangle of concern

The commonest site for bleeding in thyroidectomy is the ‘triangle of concern’, comprising the

  • trachea medially
  • RLN nerve laterally,
  • with the thyrothymic ligament and loose fat above the sternum at the base and
  • Berry’s ligament at the apex

This triangle has the small branches of small branches of the inferior thyroid artery that require meticulous haemostasis with in the vicinity of RLN, which can cause injury to nerve.

References

  1. Kumar, Prem & Premkumar, Anandan. (2018). The rationale of triangles in relation to thyroid surgery: A proposed unified ‘area of danger’ for safe thyroidectomy. 48. 10.18231/2581-5229.2018.0013.
  2. Jain, Vikas. (2017). Beahrs’ Triangle: The Surgical Anatomy. World Journal of Endocrine Surgery. 9. 35-35. 10.5005/jp-journals-10002-1206.
  3. Upile T, Jerjes W, Mahil J, Tailor H, Balakumar R, Rao A, Qureshi Y, Bowman I, Mukhopadhyay S. How to do it: the difficult thyroid. Head & neck oncology. 2011 Dec;3(1):54.

Meet the author

Dr Sanu P Moideen is an Indian-born oto-rhino-laryngologist (ENT) based in Cochin, Kerala, India. He is currently working as Post-Doctoral Fellow in Head and Neck Oncology at Regional Cancer Center, Trivandrum, Kerala.

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