The objective of this study is to compare shoulder and neck morbidity and the effectiveness of cervical lateral nodal dissection in patients with differentiated thyroid cancer and lateral metastases between the anterior and posterior approaches to the sternocleidomastoid muscle (SCM)

The incidence of thyroid cancer has increased in recent decades, being responsible for 586,000 cases worldwide, ranking ninth in incidence in 2020. The rapid increase of thyroid cancer, particularly papillary thyroid cancer, has been largely attributed to the increasing use of ultrasound, along with increased use of other imaging modalities.

Similarly, analyzing the pattern of lymph node dissemination of well-differentiated thyroid carcinoma, Eskander et al., 2 reviewed all the pertinent literature up to 2011 (a total of 1,145 patients and 1,298 neck dissections) and reported an overall metastasis rate in patients taken to to surgery of 53.1%, 15.5%, 70.5%, 66.3%, 7.9% and 21.5% in levels IIa, IIb, III, IV, Va and Vb, respectively. For the Thus, the primary surgical treatment for lateral neck disease generally includes lateral neck dissection in conjunction with total thyroidectomy. Lymph node dissection should be performed in patients with biopsy-proven metastatic lateral cervical nodes. Jugular nodes located at levels II, III, and IV are the lateral neck compartments most commonly affected by CBDT and should be included in all therapeutic lateral neck dissections. Level V, which represents the posterior triangle of the neck, is affected less frequently. However, the Vb level must be dissected along with the other levels, and careful visualization and dissection of the spinal accessory nerve is paramount. Level V can be approached by an anterior approach by retracting the sternocleidomastoid muscle posteriorly, or by dissecting the posterior triangle behind the muscle sternocleidomastoid to the trapezius muscle. The precise extent of the neck dissection is a decision made based on the volume and location of the disease. The ATA recommends complete lymph node dissection (CLND), including levels II and V, for most patients with clinically evident lateral neck metastatic disease, although nuances regarding the extent of level V dissection are not clarified, in relation to whether level V should be included. Regarding the difference between the surgical techniques, the posterior approach to the sternocleidomastoid muscle involves a longer incision, where the dissection proceeds from the anterior edge of the trapezius muscle in a medial direction that includes the lymphatic contents of the supraclavicular fossa. The upper margin of this area presents the greatest risk of damage to the spinal accessory nerve. Furthermore, during the dissection of this region, several supraclavicular branches of the cervical plexus can be found. Some branches of the deep cervical plexus follow a course similar to that of the accessory nerve and may confuse the novice surgeon. In the case of the anterior approach, the incision is made up to the anterior edge of the ECM and once the accessory nerve has been identified at its insertion in the sternocleidomastoid, its course is traced superiorly to the posterior belly of the digastric. However, the effect of the anterior approach on the lymph node count and the risk of future recurrence at level V is uncertain. With these differences in terms of the approach in these two techniques, a greater length of skin incision, and greater dissection of the accessory nerve can be observed. and of the deep cervical plexus given the similar course to the XI nerve in the posterior approach, the question arises as to whether the surgical approach influences the patient's morbidity.

The main objective of the present study was to compare the morbidity and effectiveness measured in terms of lymph node count of emptying levels II to V by the anterior versus the posterior route in patients with well-differentiated thyroid cancer with lateral metastases.

Inclusion Criteria:

1. Patients ≥ 18 years.
2. Patients with macroscopic lymph node involvement identified by physical examination, imaging or intraoperatively in lateral neck.
3. Patients with microscopic nodal involvement confirmed by FNAB (definition by the pathologist of suspected or confirmed metastatic papillary carcinoma according to the Bethesda criteria)
4. Candidates for lateral lymph node dissection due to suspected or confirmed disease metastatic lymph nodes as defined by the treating surgeon.
5. Patients requiring or not requiring thyroidectomy and/or central dissection concomitant with the dissection

Exclusion Criteria:

1. Patients with a history of previous neck dissection
2. Histological confirmation of medullary or anaplastic carcinoma
3. Previous spinal nerve injury

Single (Participant)