Clinical outcomes of subxiphoid uniportal video-assisted thoracoscopic thymectomy using a double sternum retractor versus conventional approaches

Introduction

Anterior mediastinal masses encompass a heterogeneous group of pathological entities characterized by varied histological profiles, including thymic epithelial tumors (TETs), thymic neuroendocrine tumors, benign cysts, etc. (1). Despite variability in histological classification, the cornerstone of treatment for anterior mediastinal masses involves surgical resection (2,3).

Median sternotomy was previously regarded as the gold standard for conducting a complete thymectomy. However, as video-assisted thoracoscopic surgery (VATS) continues to advance, characterized by reduced trauma, decreased operative blood loss, and fewer postoperative complications, it is increasingly favored for managing anterior mediastinal masses (4,5). There are many different approaches to VATS thymectomy, including unilateral or bilateral transthoracic approaches, subxiphoid approaches, and a combination of them (6). At present, the transthoracic approach is most utilized. However, patients undergoing the VATS thymectomy through the transthoracic approach often experience significant postoperative pain due to the injury of intercostal nerves (7,8).

The subxiphoid approach was first reported by Kido et al. in 1999 (9). However, it has not ascended to the primary choice for thymectomy because of several limitations, such as the constricted retrosternal region and the potential mutual interference between surgical instruments. Afterward, Suda et al. introduced using carbon dioxide (CO₂) insufflation to generate an artificial pneumothorax during the subxiphoid thymectomy (10). Zhao et al. described the subxiphoid and subcostal arch thymectomy (SASAT), which utilizes a three-portal approach for enhanced surgical access and visualization (11). The subxiphoid VATS thymectomy has gradually emerged as an alternative to transthoracic VATS thymectomy (8). However, the abovementioned methods do not effectively elevate the retrosternal superior mediastinal region. In addition, these conventional approaches are generally performed with CO₂ insufflation and multiple portals, which have been associated with a potential risk of cardiopulmonary impairment, suboptimal recovery, and cosmetic outcomes (7,12,13).

In 2013, Zielinski et al. introduced 24 thymoma resections performed through the right intercostal combined subxiphoid approach using double sternum retractors (14). Subsequently, Aramini and his colleagues reported a subxiphoid thymectomy employing a double sternum retractor with two portals (15). In this article, we first described the subxiphoid uniportal VATS thymectomy (SUVT) using a double sternum retractor without CO₂ insufflation and compared the initial findings of this innovative technique with those of traditional VATS thymectomy. We present this article in accordance with the STROBE reporting checklist (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2024-2267/rc).

Methods

Patients

This study analyzed clinical data from patients undergoing VATS thymectomy for anterior mediastinal mass at West China Hospital, Sichuan University, between June 2023 and May 2024. The surgical approach was changed in June 2023 due to the advantages of the SUVT using a double sternum retractor. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the ethics committee of West China Hospital, Sichuan University (No. 2024842) and informed consent was obtained from all participating patients. A total of 186 patients with anterior mediastinal masses underwent complete VATS thymectomy. Exclusion criteria for this cohort included patients who had a history of thoracic surgery, long-term use of analgesics, psychiatric cognitive impairments, or required conversion to thoracotomy. Following these criteria, 133 patients were ultimately included in our study. Patients who underwent the SUVT using a double sternum retractor were assigned to the SUVT group (Figure 1). Correspondingly, patients who underwent VATS thymectomy through the subxiphoid and subcostal arch approach or transthoracic approach were assigned to the non-SUVT group. According to the National Comprehensive Cancer Network (NCCN) Clinical Practice Guidelines in Oncology for Thymomas and Thymic Carcinomas (Version 1. 2024) and the Chinese Expert Consensus on The Diagnosis and Treatment of Thymic Epithelial Tumors (2023 Edition), the surgical objectives include complete excision of the lesion, encompassing total thymectomy, resection of the mass, removal of pericardial fat tissue, and clearance of contiguous or noncontiguous disease (16,17). Therefore, all patients in the SUVT group, regardless of the presence of myasthenia gravis (MG), underwent extended thymectomy. In the non-SUVT group, only patients with MG underwent extended thymectomy, while other patients underwent total thymectomy. D.T. performed the SUVT procedures, while the non-SUVT procedures were performed by other surgeons in the Department of Thoracic Surgery from West China Hospital, Sichuan University.

Figure 1 The diagram of patients enrollment.

Data collection

The clinicopathological features were collected, including demographics, operation time, intraoperative blood loss, postoperative complications, the time and volume of postoperative chest drainage, and the postoperative hospital stay. Additionally, the radiological and pathological information of anterior mediastinal masses was evaluated. The diameter and location of the masses were measured by reviewing computed tomography (CT) images by one experienced thoracic surgeon (L.M.) and radiologist (C.Z.). The boundaries of the superior mediastinum were defined as the level between the sternal angle to the inferior margin of the fourth thoracic vertebrae, as we previously described (18). The Visual Analog Scale (VAS) pain score was used to evaluate patients’ pain on postoperative days 1, 3, 7, and 30.

Operation

Installation of the double sternum retractor: the preparation for thymectomy

A 4 cm vertical incision from the upper edge of the xiphoid process. One sternum retractor was positioned behind the lower portion of the sternum, and the second sternum retractor was placed behind the manubrium, situated at the suprasternal fossa. Each hook was then connected to a traction frame via two retractors. During the operation, the surgeon manipulated the device to lift the sternum gradually by elevating the retractor. This action typically created an adequate visual field and operative space, achieved by raising the lower hook by more than 10 cm and the upper hook by over 5 cm. The height of the sternum hooks could be adjusted to meet the operation’s specific requirements, ensuring optimal surgical access and facilitating a successful procedural outcome. The double sternum retractor we used was manufactured by Jiangsu Suchuang Medical Devices Co., Ltd. and Hangzhou Chuangmeng Medical Equipment Co., Ltd., commercially termed the Mediastinal Exposure Sternum Retractor.

The SUVT using the double sternum retractor

The SUVT using the double sternum retractor was performed with the patient in a supine-lithotomy position. The primary surgeon stands between the patient’s legs, while an assistant responsible for operating the camera scope is positioned on the patient’s right side (Figure 2).

Figure 2 The panoramic view of SUVT using a double sternum hook retractor. SUVT, the subxiphoid uniportal video-assisted thoracoscopic surgery thymectomy.

The surgeon dissected the retrosternal space up to the level of the left innominate vein. Subsequently, the anesthesiologist modified the ventilation settings to facilitate the collapse of the right lung, optimizing the surgical field visibility. Utilizing the right phrenic nerve as the boundary, the detachment of the prepericardial thymus and surrounding adipose tissues initiated on the right side of the mediastinum. The entire process should expose the critical anatomical landmarks of great vessels, trachea, and pericardium.

The right lung was re-expanded after the procedure on the right side of the mediastinum. In contrast, the left lung collapsed to enhance visibility and detached in the left mediastinal pleural. Upon revealing the distal end of the left innominate vein, the dissections from both sides of the mediastinum converged (Figure 3). For some certain excessively large masses, the upper left pole of the thymus can be detached to facilitate the overall traction of the masses and achieve complete resection. The resected mass was carefully preserved at the bottom of a specimen bag and retrieved through the subxiphoid incision. The details of the SUVT were presented in Video 1. The procedure was performed via direct manipulation and endoscopic assistance without traditional ports or retractors. To address potential contamination risks, we implemented strict safety measures: (I) rigorous aseptic protocols for surgical field and endoscope sterility; (II) sterile saline irrigation to clear contaminants; (III) standardized postoperative anti-infection care.

Figure 3 The endoscopic view of SUVT using a double sternum hook retractor. The adipose tissue around the thymus was removed, and the aortic arch, the brachiocephalic trunk, the left common carotid artery, the left subclavian artery, the left innominate vein, the right innominate vein and the trachea was fully exposed. SUVT, the subxiphoid uniportal video-assisted thoracoscopic surgery thymectomy.

The VATS thymectomy via subxiphoid and subcostal arch approach and transthoracic approach

During the procedure of VATS thymectomy utilizing conventional approaches, multiple portals are typically established to facilitate the insertion of surgical instruments. For the SASAT, a vertical port is created caudally to the xiphoid process, with the other two ports positioned under the bilateral costal arches. Subsequently, an artificial pneumothorax is induced via CO₂ insufflation at a positive pressure of 8 cmH₂O (11). Similarly, the transthoracic approach involves placing an observation port in the 6th intercostal space along the anterior axillary line, with two primary operation ports positioned in the 3^rd intercostal space at the anterior axillary line and in the 5^th intercostal space at the midclavicular line, respectively (7).

Postoperative management

All patients were administered analgesia with nonsteroidal targeted analgesics until the drainage tube was removed. The chest tube was removed once the drainage volume decreased to less than 200 mL/day. The patients were discharged following confirmation of normal chest X-ray or CT results. The patient’s pain level using the VAS score was evaluated on postoperative days 1, 3, 7, and 30.

Statistical analysis

Statistical analysis was conducted using SPSS 25.0 (SPSS, Chicago, IL, USA, www.ibm.com/software/analytics/SPSS). Measurement data were expressed as mean ± standard deviation and categorical data were expressed as frequencies and percentages. The Chi-squared and Fisher’s exact tests were used to analyze categorical data. The independent samples t-test was used to compare the continuous variables between all groups using different approaches. A P value of<0.05 indicated statistical significance, and all analyses were two-tailed.

Results

Patient

The study included 41 patients who underwent the SUVT using a double sternum retractor (SUVT group) and 92 patients who underwent thymectomy via subxiphoid and subcostal arch approach (SASAT group) or transthoracic approach (transthoracic group). This cohort comprised 66 men and 67 women aged 17 to 80 years.

The SUVT group versus the non-SUVT group

The patient demographic characteristics, operative data, clinical outcomes, and pathological diagnosis are summarized in Table 1. The demographic characteristics, operation time, intraoperative blood loss, the time and volume of drainage duration, postoperative hospital stay, and VAS on the postoperative 1^st day did not differ significantly between the two groups (all P>0.05). Compared to the non-SUVT group, the SUVT group demonstrated significantly lower VAS pain scores on the postoperative 3^rd day (0.7±0.7 vs. 1.5±0.8, P<0.001), 7^th day (0.1±0.3 vs. 1.2±1.3, P<0.001), and 30^th day (0.0±0.0 vs. 0.7±0.9, P<0.001), larger mass size (5.18±2.59 vs. 3.46±1.83 cm, P<0.001), and a higher incidence of masses located in the superior mediastinum (17 vs. 14, P<0.001). Subsequently, we classified the non-SUVT group into the SASAT and transthoracic groups and analyzed the difference with the SUVT group (Table S1). The indicators showed similar significant differences compared to the SASAT or transthoracic groups (all P<0.05). The pathological evaluations confirmed the complete resection of masses in all cases. Among all patients, 68 (51.1%) were diagnosed with TETs, 42 (31.6%) with benign cysts, 12 (9.0%) with hyperplastic thymus, and 11 (8.3%) with lymphoma, lymphadenopathy, or teratoma. The World Health Organization (WHO) classification and tumor-node-metastasis (TNM) staging for patients diagnosed with TETs were illustrated in Table 2. Notably, there was a statistical difference in the WHO classification between the two groups (P=0.02), and a higher TNM staging of TETs was observed in the SUVT group (P=0.004).

Therapeutic efficacy in patients with MG

Table S2 details the information of 16 patients diagnosed with MG who underwent extended thymectomy, with 5 patients in the SUVT group and 11 patients in the non-SUVT group. According to the Myasthenia Gravis Foundation of America (MGFA) classification, the distribution of patients was as follows: 3 patients were in stage I, 8 in stage IIa, 1 in stage IIb, 2 in stage IIIa, 1 in stage IIIb and 1 in stage IVa. Among them, all patients in the SUVT group experienced relief of symptoms (1 in stage I, 3 in stage IIa, and 1 in stage IIIa), whereas, in the non-SUVT group, 4 patients (1 in stage I, 2 in stage IIa and 1 in stage IIb) reported a reduction in symptoms. Regarding postoperative complications, two patients in the SASAT group experienced a postoperative pulmonary infection, and one patient in the SASAT group experienced arrhythmias. No postoperative complications specifically related to surgical wounds, endoscope contamination, or surgical site infections were observed in either the SUVT or non-SUVT groups. During the ongoing follow-up period, no recurrence or deaths have occurred.

Discussion

Currently, VATS thymectomy has supplanted the median sternotomy as the preferred method for resecting anterior mediastinal masses (8). In this article, we described a novel technique: the SUVT using a double sternum retractor without CO₂ insufflation. This is the first study to compare this innovative technique with other traditional VATS thymectomy to investigate its efficacy and safety.

In our study, the diameter of masses in the SUVT group was significantly larger than that in the other group. This result was consistent with the report of Song et al. in 2022 (19). The subxiphoid approaches with a double elevation of the sternum could more efficiently harvest the larger specimens. Furthermore, our analysis revealed that more masses located in the superior mediastinum were more completely resected through the SUVT using a double sternum retractor. The subxiphoid approach affords superior exposure of the left innominate vein and the upper poles of the thymus, thereby facilitating more effective surgical resection of mediastinal masses situated in the superior mediastinum. The above demonstrated that this technique may particularly benefit patients with larger or superior mediastinal masses. Additionally, the importance of complete mass resection for the prognosis of patients has been well-documented in previous studies (7,20).

The average operation time of SUVT groups was shorter than the previous study reported by Song and colleagues, who created two portals (19). Our result indicated that the operation time in the SUVT group is comparable to that in the non-SUVT group despite the presence of more masses with larger diameters or located in the superior mediastinum in the SUVT group. This is likely because the double sternum retractor created ample vision and operating space, which improved the endoscopic view and minimized the interference of the heart and great vessels during mass resection. This elevation device increased the gap and tension between the mass, adipose tissue, heart, and blood vessels, facilitating easier mass separation. Our technology provides a more complete thymus and adipose tissue removal strategy with reduced operation time.

The safety of thymectomy via the subxiphoid and subcostal arch approach and transthoracic approach has been well-established (20-23). Our research found that the SUVT and non-SUVT groups did not differ significantly in terms of intraoperative blood loss, the time and volume of drainage duration, and postoperative hospital stay. The operation time in the SUVT group was not extended, even in the presence of larger masses or those located in a superior position. The complete resection of the masses is an important determinant of the success of thymectomy, directly impacting patient outcomes. However, because of the narrow retrosternal space, this goal also increases the risk of intraoperative injury to the innominate vein, superior vena cava, and other vascular structures. Introducing the double sternum retractor into the surgical procedure significantly mitigates these risks. By elevating the sternum, this tool improves visibility and access to the upper mediastinum and adjacent areas, thereby reducing the likelihood of inadvertently damaging the phrenic nerves, major blood vessels, and other vital structures. This enhanced exposure and control offer a safer operative environment, crucial for minimizing complications while ensuring thorough mass resection. Song et al. reported that intraoperative blood loss, indwelling drainage tube, and postoperative hospital stay increased significantly in two-portal subxiphoid VATS with double elevation of the sternum group compared to the uniportal intercostal VATS (19). They conjectured that the increased wound size following the dissection of thymic tissues was a primary contributor to the heightened drainage volume and extended postoperative hospital stay longer. Nevertheless, we did not obtain the same results in our study. This divergence may be related to the different inclusion and exclusion criteria. Our study included only 8 patients with pathological diagnosis of thymic carcinoma. In contrast, Song et al. additionally included more patients with mixed and rare type thymoma, thymic carcinoma and thymic neuroendocrine carcinoma, whose additional treatment operons, such as systematic anterior mediastinal and deep mediastinal lymph node dissection, might account for the heightened drainage volume and longer postoperative hospital stay time.

The transthoracic approach is generally associated with injury to the intercostal nerve, exacerbating postoperative pain (6,7). By avoiding the intercostal area, the subxiphoid approach reduces the risk of intercostal nerve injury, significantly minimizing postoperative pain and enhancing patient recovery (7). By selecting the subxiphoid approach, our method minimizes postoperative pain and enhances patient recovery more effectively than traditional approaches. Furthermore, unlike the three portals typically used in the SASAT, our technique requires only a single incision for the entire procedure. This not only benefits the patients who undergo the SUVT using a double sternum retractor for experiencing the lowest levels of postoperative pain but also offers superior cosmetic outcomes due to the reduced number of incisions.

The SUVT using a double sternum retractor did not demonstrate a significant advantage in patients’ pain on the first postoperative day. This result might be attributed to the subjective discomfort associated with the postoperative placement of a chest tube, which could mask the early pain reduction benefits of this technique. The distinct advantages of the double sternum retractor in alleviating pain become more evident after removing the chest tube, suggesting that the initial discomfort possibly contributes to the early postoperative pain levels. Many studies suggest that omitting chest tube drainage does not increase the risk of adverse events in patients undergoing subxiphoid thymectomy (24,25). In our study, chest drains were omitted in 6 patients, resulting in no complications and a significant reduction in reported pain levels.

There were several limitations in our study. First, differences in surgeons between the SUVT and non-SUVT groups introduced potential performance bias, necessitating cautious interpretation of the results. Second, while the SUVT approach enables minimally invasive treatment for patients with larger or superior mediastinal masses that are unsuitable for the non-SUVT approach, the inherent heterogeneity in mass size and location between groups reflects unavoidable selection bias in clinical practice. This bias stems from the SUVT approach specific indications for complex cases. In future studies, we plan to mitigate such bias through rigorous study designs, including standardized surgical training protocols, randomized controlled trials, or multicenter collaborative studies. Finally, the relatively short follow-up period of this study limits the generalizability of the findings. A longer follow-up period with larger sample sizes is required to validate our results comprehensively.

Conclusions

Compared with the traditional subxiphoid and subcostal arch approach and the transthoracic approach, the SUVT using a double sternum retractor enables patients to experience less postoperative pain and achieve better cosmetic results. Moreover, the SUVT using a double sternum retractor may provide a new treatment option for patients with anterior mediastinal tumors, demonstrating superior potential in achieving complete resection of masses. This is particularly relevant for larger masses or those located in the superior mediastinum, where traditional approaches may face limitations.

Acknowledgments

We sincerely appreciate the invaluable technical guidance provided by Professor Jiang Fan, Professor Wei Huang and their team at the Department of Thoracic Surgery from Shanghai General Hospital.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2024-2267/rc

Data Sharing Statement: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2024-2267/dss

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2024-2267/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2024-2267/coif). D.T. serves as an unpaid editorial board member of Journal of Thoracic Disease from March 2025 to February 2026. The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the ethics committee of West China Hospital, Sichuan University (No. 2024842) and informed consent was obtained from all participating patients.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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