Introduction

According to Global Cancer Statistics 2020, it was estimated that there were 586,000 thyroid cancer cases, ranking 9th in cancer incidence worldwide1. Differentiated thyroid cancer (DTC) accounts for more than 90% of all thyroid histological types, and papillary thyroid carcinoma (PTC) is the most common histological type of DTC2.

Radical surgical treatment is the first choice for DTC, which is an essential element in decreasing cancer recurrence and metastasis3. In the past 20 years, outstanding achievements have been achieved in radical resection, scar minimization, and protection of essential glands and nerves in endoscopic thyroidectomy4,5. Several researchers have suggested that endoscopic thyroidectomy can meet the needs of radical resection, functional protection, and cosmetic purposes compared to conventional thyroidectomy6. The endoscopic approach includes transaxillary and bilateral axillary and breast access, retroauricular and transoral route7. In China, in the scarless neck endoscopic thyroidectomy (SET), the anterior chest approach is preferred outside the neck8.

In current clinical practice, closing the platysma muscle layer after open thyroidectomy or suturing the linea alba cervicalis after endoscopic thyroidectomy seems to be recommended as a standard procedure9. However, there is a lack of sufficient evidence for the efficacy and feasibility of this practice, and so far, there have been no reports related to the potential clinical benefits of endoscopic thyroidectomy without suturing the linea alba cervicalis.

In addition, due to the establishment of the endoscopic space in the loose connective tissue under the neck and chest, cavity complications, such as subcutaneous effusion, infection, and fat necrosis, may occur after the operation, which affects the wound healing time and the quality of life of patients10. Presently, the complications related to cavity construction mainly rely on the intraoperative grasp of the surgical level and the separation direction, which is associated with the technical level of the surgeon. However, there are still no satisfactory prevention and treatment measures.

Negative pressure wound therapy(NPWT), which emerged as an advanced therapy in wound healing, has been broadly applied in acute and chronic open wounds and closed surgical incisions11. However, no one has studied the effect of NPWT on the prevention of cavity-related complications after endoscopic thyroidectomy through the chest-breast approach. NPWT, also known as “vacuum-assisted closure therapy,” was first proposed for modulating wound healing in 199712. NPWT enables the stabilization of the wound environment, reduces wound edema, decreases bacterial burden, improves topical blood circulation, stimulates growth factor expression, and promotes the growth of granulation tissue and angioneogenesis13,14,15, and for the closed surgical incisions, can help to reduce complications of wound dehiscence, infection, hematoma, and seromas13,14,16.

Endoscopic thyroidectomy via chest-breast approach requires free anterior subcutaneous neck and chest space17. Complications followed by building endoscopic space after surgery are worthy of our attention. According to our clinical experience, postoperative cavity-related complications can prolong the hospital stay and increase the risk of infection. To prevent and solve this problem, we do not suture the cervical white line, but we use NPWT after endoscopic thyroidectomy through the chest-breast approach to evaluate the effect. In this study, we conduct a retrospective collection of patients treated by endoscopic thyroidectomy via the chest-breast approach to assess the feasibility and efficacy of this strategy.

Methods

Study design and patients

A total of 142 patients from May 2021 to February 2023 in the Department of General Surgery, the Second Affiliated Hospital, Xi’an Jiaotong University were enrolled and divided into 2 groups, including 71 individuals in the improvement group (no suture of the linea alba cervicalis) and 71 in the conventional group (suture the linea alba cervicalis). This study is a retrospective case-control study. All written informed consent was obtained from patients before the operation, and the study was approved by the Ethics Committee of the Second Affiliated Hospital of Xi’an Jiaotong University (No.2023318). All experiments were performed in accordance with relevant guidelines and regulations.

Participants

Inclusion criteria

(1) Patients who underwent endoscopic thyroidectomy via the chest-breast approach; (2) Patients with benign or papillary thyroid tumors confirmed by postoperative pathology; (3) Preoperative evaluation using cervical ultrasound or computed tomography (CT) showing thyroid tumors had no external invasion and distant metastasis; (4) Patients with cosmetic needs.

Exclusion criteria

(1) Patients with secondary thyroid surgery or previous radiofrequency thyroid ablation; (2) Patients who have been previously treated with other neck surgery or radiotherapy; (3) Patients converted to open thyroidectomy; (4) Surgical contraindications that cannot tolerate general anesthesia and surgery, such as severe heart failure, coagulation dysfunction; (5) cases with incomplete clinical data.

Operative procedure

Patients in both groups were treated with general anesthesia by endotracheal intubation. Patients were supine with their heads elevated and legs separated, with a shoulder pad allowing for a certain extent of neck overextension. Then, the medical staff performed routine disinfection and towel laying. A surgical incision, which served as an observation port, was made with a length of approximately 10 mm and a depth into the subcutaneous fascia’s superficial layer on the right areola’s medial margin. Next, the “inflation liquid,” a mixture of 1 mg adrenaline and 500 ml normal saline, was subcutaneously injected into the subcutaneous deep fascia to distend subcutaneous tissues, preparing for the next step of separating the subcutaneous tissue toward the suprasternal fossa using a subcutaneous separation stick. A 10 mm trocar was placed to introduce a laparoscope. CO2 was continuously injected to maintain a pressure of 6 mmHg. Three incisions measuring 5 mm in length were made respectively at the 11-o’clock positions on the left and right edges of the areolas, then three 5 mm trocars were inserted through the incisions, which served as the primary and auxiliary operation approach. After the subcutaneous tunnels were successfully created, the ultrasonic scalpel and toothless graspers were performed through operation ports to separate the anterior cervical subcutaneous loose connective tissues up to the cricoid cartilage plane and laterally to the inner margin of the sternocleidomastoid (Fig. 1a and b). The linea alba cervicalis was cut open with the ultrasonic scalpel, and then the bilateral infrahyoid muscles were sutured and suspended to expose the thyroid gland (Fig. 1c and d). The operative method of thyroidectomy was based on the guidelines of the American Thyroid Association (ATA), and a right-side thyroid lobectomy or a total or near-total thyroidectomy was performed based on the tumor’s size, location and benign or malignant nature. After surgery, the negative pressure drainage tube was placed in the deep surface of the strap muscles through the subcutaneous tunnel and fixed on the left areola incision site (Supplementary Fig. S1A). Finally, all patients are treated with NPWT on the chest (Supplementary Fig. S1B and S2).

Fig. 1
figure 1

Endoscopic thyroidectomy operative procedure. (a) Chest-breast approach. (b) Laparoscope and operative device. (c) Cut the linea alba cervicalis open with ultrasonic scalpel. (d) Expose thyroid gland.

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Alterations

Improvement group: after careful examination, no bleeding was observed in the operation area, and no closure of the linea alba cervicalis was performed to evaluate drainage efficacy(Fig. 2a and b).

Fig. 2
figure 2

(a) No closure of the linea alba cervicalis (case 1). (b) No closure of the linea alba cervicalis (case 2). (c) Closure of the linea alba cervicalis (case 3). (d) Closure of the linea alba cervicalis (case 4).

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Conventional group: after careful examination, there was no bleeding in the operation area, and absorbable sutures were used to close the linea alba cervicalis(Fig. 2C and D).

Outcomes

Generally considered outcomes were age, gender, body mass index(BMI), combination with hypertension, diabetes or Hashimoto’s thyroiditis, number of lesions, largest tumor size, type of histopathology, incidence of lymph node metastasis, operation time, the intraoperative blood loss, the surgical resection extent, the postoperative drainage volume, postoperative hospital stays and the overall incidence of postoperative complications including temporary recurrent laryngeal nerve(RLN) injury and transient hypocalcemia, the incidence of neck edema and the score of Visual Analogue Scale(VAS) of 5 days after the operation.

Statistical analysis

SPSS 26.0 was used for statistical analyses to compare the two groups’ differences. The continuous variables were expressed as mean ± standard deviation and analyzed using the independent-sample t-test or Mann-Whitney U test according to its distribution pattern. Categorical variables were expressed as frequency (percentage) and analyzed using Chi-square or Fisher exact test as appropriate. Statistical significance was recognized with P < 0.05.

Results

Basic characteristics

The basic characteristics of all patients were summarized in Table 1. These basic outcomes had no significant differences (P > 0.05).

Table 1 Comparison of basic characteristics between improvement and conventional group.
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Pathological characteristics

There were no significant differences in the largest tumor size, histopathology type, or lymph node metastasis incidence (P > 0.05), as shown in Table 2.

Table 2 Comparison of pathological characteristics between improvement and conventional groups.
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Surgical outcomes

No statistically significant differences were observed in terms of the operation time, the intraoperative blood loss, the surgical resection extent, the postoperative drainage volume, postoperative hospital stays, and the overall incidence of postoperative complications, including temporary RLN injury and transient hypocalcemia between the two groups (P > 0.05). There are no cases of superior laryngeal nerve injury, hematoma, tracheal and esophageal injury, and lymphatic leakage. There were statistical differences in the incidence of neck edema (3/71,4.2% vs. 10/71,14.1%) and the score of VAS of 5 days after the operation (3 ± 1.2 vs. 4 ± 1.3) between the two groups (P < 0.05) (Table 3).

Table 3 Comparison of surgical outcomes between improvement and conventional group.
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Subcutaneous effusion after endoscopic thyroidectomy through thoracic approach

All patients were successfully treated with NPWT. Results showed that gender, age, histopathology, combination with hypertension, diabetes, and Hashimoto’s thyroiditis, largest tumor size, number of lesions, suturing or not the linea alba cervicalis, and surgical resection range were not the risk factors that obviously could affect the occurrence of subcutaneous effusion, as shown in Table 4.

Table 4 Risk factors of postoperative subcutaneous effusion.
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The therapeutic effect of NPWT on wound healing after endoscopic thyroidectomy

The overall incidence of cavity-related complications in all patients was 3.52% (5/142), and the overall orifice healing rate was 96.48% (137/142). Mild dermatitis and blister incidence were 9.15% (13/142) and 4.93% (7/142), respectively. No patients developed severe dermatitis and infection after the use of NPWT. There were no significant differences in the incidence of postoperative subcutaneous effusion (3/71,4.23% vs. 2/71,2.82%), mild dermatitis (7/71,9.86% vs. 6/71,8.45%), blister (3/71,4.23% vs. 4/71,5.63%) between the improvement and conventional groups (P > 0.05), as shown in Table 5.

Table 5 Analysis of the therapeutic effect of NPWT after endoscopic thyroidectomy.
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Discussion

Nowadays, endoscopic thyroidectomy has been widely applied to treat thyroid diseases in many countries. With its characteristics of both “treatment and beauty,” endoscopic thyroidectomy has gradually attracted attention and made significant progress in the medical field, which can be performed by axillary, axillary-breast, anterior chest-breast, transoral, and retro auricular approaches18,19. Breast approach endoscopic thyroidectomy(BAET) is the most widely used one in clinical practice, which was first reported by Ohgami in 200020. The previous study demonstrated that BAET has significant advantages in cosmetic results and operation outcomes, including (1) Clothes can easily cover the scars after surgery to achieve no scar in the neck, which dramatically reduces psychological pressure on patients; (2) The operation space is large enough to make the thyroid gland exposed clearly, which would enable surgeons to perform bilateral resection at the same time and selective lymph node dissection; (3) A wide range of indications that make it possible to perform difficult endoscopic thyroidectomy8,21. However, some hold the opposite opinion that SET, transferring the scars to an area concealed by clothing, is not a minimally invasive technique but a maximally invasive one with a more cumulative length of scars in the anterior chest, a longer operative time and more incredible postoperative pain22.

In recent years, robotic thyroidectomy has been increasingly applied in the treatment of thyroid carcinoma. The robotic system could overcome the limitations of endoscopic thyroidectomy, provide a 3-D field of view, and improve instrumental dexterity23. A study has revealed that robotic transaxillary thyroidectomy had a shorter total operative time, especially for the inferior pole dissection and the identification of parathyroid glands(PTGs) and the RLN. The incidence of postoperative outcomes had no significant difference with fewer sacrificed PTGs24. Another retrospective study including 240 individuals with PTC was performed to compare the surgical outcomes of these two types of transoral methods, indicating that robotic thyroidectomy has the advantages of central compartment node dissection, shorter hospital stays, and 48 h postoperative pain score in PTC25. Nowadays, thyroid surgeries are becoming more comprehensive. Therefore, more attention should be paid to preventing and reducing cavity complications.

Closing the platysma muscle layer after open thyroidectomy or suturing linea alba cervicalis after endoscopic thyroidectomy is a standard procedure in clinical practice9,26,27. However, there is insufficient evidence of potential benefits for patients in preventing postoperative complications. On the one hand, suture can reduce wound space, which helps minimize fluid accumulation and promote wound healing; on the other hand, suture material may lead to granuloma formation as a type of foreign body, which might negatively influence postoperative pain and cosmetic results. Controversy also exists in abdominal surgery. It is considered that suturing peritoneum accords with the anatomical characteristics, which could reduce the occurrence of postoperative adverse consequences, including abdominal adhesion, incision hernia, and incision infection. The short-term outcomes, such as saving operation time and reducing postoperative pain, are inconsistent with the surgery’s primary purpose. However, the latest view is that not suturing the peritoneum does not increase the incidence of complications but also has the advantages of reducing abdominal wall tension, shortening operation time, reducing intraoperative blood loss, and relieving postoperative pain28,29,30. Some trials have been conducted to determine whether there is a difference between platysma muscle sutures versus no after thyroid surgery on the operation time, wound complications, and cosmetic outcome31,32. These results have preliminarily proved no significant clinical benefits of suturing the platysma muscle in open thyroidectomy. Although there is no need to cut open the platysma muscle during endoscopic thyroidectomy, this practice provides a reference for no suturing of the linea alba cervicalis. In our study, no closure of the linea alba cervicalis resulted in a lower incidence of neck edema and less postoperative pain with no significant differences in surgical outcomes, which may be due to the aseptic inflammatory reaction in the tissue caused by suturing the linea alba cervicalis.

Nowadays, the most commonly used methods for measuring pain intensity are the VAS, Verbal Rating Scale (VRS), Numerical Rating Scale (NRS), and Faces Pain Scale-Revised (FPS-R)33. VAS is widely used to rate pain intensity. It usually consists of a 10 cm straight line with a demarcation of two ends “no pain” to the left and “the worst possible pain” to the right, and then the patient is asked to mark on the line the point that best represents the intensity of their pain34. VAS has the advantages of simplicity, easy understanding, low cost, and short time consumption35. However, it has also several limitations. For example, the assessment of pain intensity relies on patients’ subjective evaluations34,36. Therefore, objective methods are necessary to assess patients’ postoperative pain in clinical practice. Recently, a meta-analysis revealed that the water swallow test (WST) had a better diagnostic performance in surgical patients with head and neck cancer37. Typically, a specific volume of water (30 ml) is given to the patient to swallow, and dysphagia patients are screened by observing several key factors, such as the number of swallows, the time taken, and the presence of airway responses such as coughing and choking, and level III and above indicate abnormalities38. Some other screening based on WST exhibited excellent potential in identifying oropharyngeal dysphagia in postoperative head and neck cancer patients39. We are considering using WST to assess patients’ swallowing function after endoscopic thyroidectomy.

Hematoma after thyroidectomy can be a potentially life-threatening complication. Hematoma is associated with male sex, older age, black race, hypertension, diabetes, inflammatory thyroid disease, chronic kidney disease, partial thyroidectomy, and bleeding disorders40,41. To prevent airway compression and construction, drain placement after the postoperative period is a common clinical practice to provide egress for accumulating blood and serous fluid from the surgical bed42. For endoscopic thyroidectomy, a procedure including an extensive surgical flap on the anterior chest wall could also raise the risk of postoperative bleeding and effusion, and the key to reducing hemorrhage and flow is to separate at the correct anatomical level-superficial layer of deep fascia10,43. In addition, applying pressure bandaging on the chest wall is routinely performed as a conservative treatment after surgery.

NPWT is widely accepted in treating wounds through increased perfusion, mechanical deformation-induced granulation stimulation, exudate removal, and bacterial control44. Closed surgical incisions can evenly distribute pressure on the wound surface to eliminate subcutaneous dead spaces, decrease drainage volume, and decrease the risk of infection45. Research shows that NPWT can significantly reduce closed surgical complications, including seroma, wound dehiscence, and wound necrosis, compared with traditional dressings46. In our previous study, we assessed the effect of NPWT on preventing and treating cavity-related complications after endoscopic thyroidectomy via the chest-breast approach47. 48 patients were enrolled, including 24 cases in the treatment group (NPWT group) and 24 cases in the control group (traditional compression group). With statistically significant differences(P<0.05), the incidence of subcutaneous effusion in the NPWT group was lower compared with the control group. We observed that the postoperative chest discomfort of patients treated with NPWT was less than that of the control group. As far as we know, this is the first attempt to apply NPWT after endoscopic thyroidectomy through the chest-breast approach, which provides a potential method for reducing cavity-related complications. In this study, patients who underwent endoscopic thyroidectomy via chest-breast approach were treated with NPWT after surgery, and the overall wound healing rate was 96.48%. 5 patients had subcutaneous effusion after surgery, of which 2 cases in the conventional group and 3 cases in the improvement group recovered gradually after improved drainage and part change of dressing. No significant differences were observed in the incidence of mild dermatitis and tension vesicle between the two groups, which are safe and effective.

Nevertheless, this study has several limitations. Firstly, the sample size is insufficient, and larger sample sizes are necessary to confirm our findings. Secondly, this study cannot evaluate the degree of postoperative pain due to the lack of objective relevant indicators. Finally, the follow-up time is too short to investigate the long-term outcomes thoroughly.

Conclusions

No closure of linea alba cervicalis is safe and feasible after endoscopic thyroidectomy, with significant postoperative benefits, including less incidence of neck edema and pain and no significant difference in the incidence of postoperative complications. Combined with the application of NPWT after thyroidectomy, this new method should be paid more attention to prevent and reduce cavity-related complications.