Perioperative outcomes of uniportal robotic-assisted thoracic surgery (U-RATS) for lung resection: state of the art—a narrative review

Introduction

Background

Robotic-assisted thoracic surgery (RATS) is a minimally invasive surgical technique with complex but precise movements, an extended range of movements, an enhanced three-dimensional (3D) view, better comfort for the surgeon and the ability for controlled teaching through dual consoles (1,2).

The evolution of minimally invasive thoracic surgery led to the development of uniportal video-assisted thoracic surgery (U-VATS) over the past several years (3). Concurrently, the use of RATS is increasing worldwide as a reliable alternative to both traditional and U-VATS (4). The converging advantages of both methods lead to the idea of performing robotic surgery through a single port. The early attempt of subxiphoid uniportal RATS (U-RATS) was conducted in 2018 and described by Gonzalez-Rivas and Ismail in 2019 on cadavers using the da Vinci Single-Port (SP) Surgical System by Intuitive Surgical (Sunnyvale, California, USA) (5).

This system has a 2.5-cm cannula, an articulating 3D camera, and 3 fully articulating instruments with 7 degrees of freedom of movement. However, some limitations were encountered with this system, which prevented the performance of standard anatomic lung resections. These problems were mainly the size of the trocar, which prevented it from passing through the ribs, the limited access offered by the subxiphoid view, the need for a 15-cm space to deploy the arms inside the patient’s body, and the absence of robotic staplers (6,7).

In September 2021 the Da Vinci Xi System was adapted to develop the U-RATS approach using robotic staplers with the first case reported in Spain (8). This was achieved after completing several cases of biportal RATS (B-RATS) and hybrid operations using thoracoscopic staplers to gain the necessary confidence (9).

Despite the description of several multiportal robotic-assisted approaches, the uniportal approach was described as less traumatic and timesaving mainly due to rapid docking and undocking which reduces the operation time and simplifies the management of possible intraoperative bleeding with the necessary experience to convert to uniportal/multiportal VATS or open surgery (10). In the multiportal robotic operations three to four ports and a 4-cm utility incision is used. CO₂ insufflation, cap seals, and 8-mm trocars or 12-mm trocars for stapling devices are the standard. The B-RATS and the U-RATS spare 3 to 4 port incisions for the patients (10).

Rationale and knowledge gap

U-RATS, a novel surgical technique introduced in 2021, has rapidly become a significant focus in thoracic surgery research. In March 2023, Wilson-Smith et al. published a systematic review detailing the perioperative outcomes from the initial cohort studies and case reports (11). Since then, further cohort studies and case reports on U-RATS perioperative outcomes have been published. Additionally, a notable knowledge gap persists in comparing the perioperative outcomes of U-RATS with other minimally invasive thoracic surgical techniques, such as multiportal RATS (M-RATS) and U-VATS.

Objective

This paper aims to present the latest state-of-the-art results from cohort studies and case reports on the perioperative outcomes of the U-RATS technique. Additionally, it seeks to compare U-RATS with other techniques where possible, to share and report on the international experience with this emerging surgical method. We present this article in accordance with the Narrative Review reporting checklist (available at https://ccts.amegroups.com/article/view/10.21037/ccts-24-26/rc).

Methods

In this review eight articles met our review criteria. An electronic based literature search on PubMed was conducted on 15 June 2024 to identify data on U-RATS for lung resections. Articles published in any language was considered. The inclusion criteria encompassed primary studies covering U-RATS lung surgery, including cohorts, case series, and observational studies. The exclusion criteria comprised secondary studies, such as literature reviews, systematic reviews, and meta-analyses. Our objective was to review the articles published to date on this emerging surgical technique to analyse the short-term peri- and postoperative experience, as this operative method is relatively new in the last 3 years. Table 1 summarises the search strategy used. The search strings were: ((((((uniportal robotic assisted lung) OR (uniportal robotic assisted thoracic)) OR (uniportal robotic assisted lobectomy)) OR (uniportal robotic assisted segmentectomy)) OR (uniportal robotic assisted pneumonectomy)) OR (uniportal robotic assisted sleeve)) OR (uniportal robotic assisted carina) (uniportal robotic-assisted thoracic surgery) OR (uniportal robotic assisted thoracic surgery). Eighty-two results were found and reviewed. Seventy-four of these articles were excluded because they were not relevant to U-RATS or lung resections or were not original articles with cohorts or case series. A total of 8 articles were read in full and analysed for the focus of this review. Table 1 summarises the search strategy and the study selection identification process is illustrated in Figure 1.

Figure 1 Flow diagram of study selection from literature. *, please see the PubMed search string used in the methods section and Table 1. U-RATS, uniportal robotic-assisted thoracic surgery.

Results

Eight cohort studies were selected for this narrative review and are presented in Table 2. Table 2 also reports the demographic characteristics and main perioperative outcomes of the included 8 cohort studies identified for use in this study (10,12-18). Although we didn’t limit the search for studies involving cohorts in uniportal robotic assisted lung resection by time, articles found were published between September 2022 and June 2024. In each of the cohorts, all patients were operated on by the same surgeon. In all articles the Da Vinci Xi system by Intuitive Surgical (Sunnyvale, California, USA) was used. Cohort size ranged from 5 and 101 patients, where only the number of patients operated on per U-RATS was taken into consideration. A total of 354 patients (60.2% male) were identified across the eight cohort studies and case reports. The mean age of the patients ranged from 58.9 to 74.0 years. Mean operation time varied between 76.0 and 216.0 minutes. Preoperative lung function was not reported in all 8 studies. The pre-operative mean predicted forced expiratory volume in one second (predicted FEV1) was between 78.9% and 94.5%. The mean size of the tumour ranged between 1.9 and 3.6 cm. All 8 studies reported the use of one chest tube.

The mean chest tube time was 1.0 to 4.8 days. The mean length of stay varied between 3.8 and 6.8 days. The perioperative mortality ranged from 0 to 20%; with the 20% being the death of 1 out of 5 patients post-operatively (17). The chosen intercostal space for the incision ranged from the 4th to the 7th intercostal space. Five out of eight studies reported the mean perioperative blood loss which ranged between 25.0 and 513.0 mL (13-15,17,18). However, the 513.0 mL reported figure was a median in a cohort of 5 patients only (17), when excluded, the range of the remaining 4 cohorts is a mean of 25.0–131.7 mL blood loss (13-15,18). Malignancy of the lung was the major indication for operation in all 8 studies. Other indications included benign tumours and infections. Four of the 8 studies reported the mean number of lymph nodes dissected which ranged from 11.0 to 17.6 lymph nodes (10,12,13,16). The most used instruments for the right hand were Maryland bipolar and the needle holder, for the left hand the fenestrated bipolar forceps. Of the 8 studies included, 5 used robotic staplers (10,12,14,16,18). Two studies utilised and demonstrated the feasibility of endoscopic staplers primarily due to the lack of availability of robotic surgical staplers at their centre (13,15). Conversions from U-RATS to another form of surgery ranged between 0% and 6.9% with a total number of 3 conversions in only 2 of the 8 studies (13,15). One conversion was to M-RATS and two conversions to U-VATS. All operations reported were anatomic lung resections including lobectomy, bilobectomy, segmentectomy, sleeve resection, extended resection and pneumonectomy.

In three of eight studies postoperative mortality was reported with one patient, which represents a total of 3 of 354 patients (0.85%). None of the included studies reported on the long-term clinical or oncological outcomes. Their primary outcomes concentrated on perioperative and short-term clinical results achieved with the U-RATS technique. The proportion of more complicated procedures such as sleeve and double sleeve resections was heterogeneous between the studies, thus the comparison of many parameters such as mean operation duration and length of hospital stay are not comparable one to one.

Discussion

Postoperative pain

Three of the eight studies reported pain scores using either the Numerical Rating Scale (NRS) or the Visual Analogue Scale (VAS) (14,15,18). Mercadante et al. measured pain at day 1, day 3, and the day of discharge post-operation using NRS (14). Kaneda et al. also used NRS, measuring pain at day 1, day 3, and 3 months post-operation (18). Ning et al. used VAS to measure pain at day 1, day 3, and day 30 post-operation (15).

Both Kaneda et al. and Ning et al. reported significantly improved short-term post-operative pain at day 1 and day 3 for patients who underwent U-VATS and B-RATS procedures, respectively. However, long-term post-operative pain was not significantly different at 3 months and 30 days post-operation, respectively (15,18). Mercadante et al. found that post-operative pain in their 24 U-RATS patients was comparable to those who had previously undergone U-VATS at their centre (14).

Challenges of U-RATS

They include the established challenges already known in multiportal M-RATS. These include the initial steep cost of procuring the robotic surgical system, the cost of maintenance, training expenses, and the additional surgical time required to overcome the learning curve (LC) (19,20). The lack of tactile feedback is another known issue.

LC

There is no study comparing the LC of U-RATS to M-RATS or U-VATS directly. A recent systematic review of 22 studies with a total of 3,246 patients receiving RATS estimated the LC needed to achieve technical proficiency at performing robotic-assisted lobectomy to be a mean of 25.3±12.6 cases (21). Within these cohorts, technical proficiency was achieved earlier at institutions where the surgeons were already considered experts in VATS or were the sole robotic surgeon at the centre (22-24). A possible reason for this is that the surgeon is used to adapting to highly magnified views, navigating around obstacles, learning through repetition and reducing blood loss to maintain visibility (23).

Docking

While the docking time of U-RATS is reportedly faster than standard M-RATS, one of the main challenges that arise in U-RATS is positioning the robotic arms to avoid collision between the trocars within a single incision (10). As a result, a limitation of the range of movement of instruments can possibly arise (10). Experience in U-VATS gave clues to small moves and manoeuvres that can avoid this. Tricks include good preoperative planning and choosing the optimal location and size of the incision depending on the target anatomy. Adjusting the trocars and their angles in the wound using the fist rule between the robotic arms and doing enough clearance also help to avoid collision between the trocars within a single incision (9,25,26).

Trocars

The use of transoral robotic trocars (TORS) can help minimise the size taken by the cuff of the trocars (9,10,26). Trocar placement parallel above the surgical wound and cross instrumentation inside the pleural cavity (14,26).

The table assistant needs to have both experiences in uniportal thoracoscopic operations as a surgeon as well as in assisting robotic operations (9,10).

Perioperative comparison of U-RATS with U-VATS and M-RATS

U-RATS combines the advantages of robotic operations with those of U-VATS including less tissue and musculoskeletal trauma, reduced postoperative pain (27), faster recovery, intraoperative blood loss (28), shorter hospital stays, better cosmetics and direct view on target anatomy. Three of the eight included studies had two patient groups: a U-RATS group and a U-VATS group, and directly compared their perioperative outcomes (16-18). Paradela et al.’s study, which compared 100 U-RATS to 100 U-VATS patients and used propensity score matching to reduce bias, demonstrated that U-RATS retrieved a significantly higher number of lymph nodes at the same number of stations. Additionally, patients who underwent U-RATS had a lower rate of postoperative complications and shorter chest drain duration than those who underwent U-VATS (16).

Stamenovic et al. retrospectively compared the outcomes of the first five U-RATS and the first five U-VATS operations conducted at their German centre, reporting an insignificant increase in operative time for U-RATS compared to U-VATS (17). Kaneda et al. found a significantly longer mean operative time in the initial 25 U-RATS compared to the initial 25 U-VATS operations conducted by the same surgeon (U-RATS =214±46.7 minutes vs. U-VATS =157±45.9 minutes; P=0.0035), suggesting that U-RATS has a longer mean operation duration during its LC than the U-VATS technique (18).

U-RATS has faster docking and undocking times compared to M-RATS. This allows for a faster conversion time to VATS or open thoracotomy in case of bleeding (9). Faster docking could also directly contribute to a shorter mean operative time. Manolache et al. compared 101 patients operated on using U-RATS by the same surgeon and assistant across centres in seven European countries with 101 patients operated on by a different surgeon and team using M-RATS at a centre in Barcelona, Spain (10). They noted that the mean operative time was statistically different (U-RATS =136±70.9 minutes; M-RATS =150±60.0 minutes; P=0.0001) and that the median length of stay was significantly lower in U-RATS than in M-RATS [U-RATS =4 (range, 1–18) days; M-RATS =5 (range, 2–31) days; P<0.0001] (10). Ning et al. compared 29 U-RATS operations with 80 B-RATS operations and found that the U-RATS procedure had a more convenient robotic arm arrangement and provided significantly lower short-term postoperative pain than B-RATS (15).

Studies suggest a more accurate lymphadenectomy and more harvested lymph nodes in U-RATS and M-RATS compared to VATS (16,29). Although standard VATS and U-VATS are widely adopted globally and generally more cost-effective than robotic surgeries, U-RATS offers several advantages. These include enhanced precision, improved 3D visualization of the surgical field, better depth perception, and reduced surgeon tremors. Additionally, the improved manoeuvrability of the surgical arms in U-RATS leads to superior lymph node dissection (16,18,30). Compared to M-RATS and B-RATS, U-RATS results in less post-operative pain, better cosmetic outcomes, and shorter mean operative times (10,15).

Strengths and limitations

Strengths

In this article, we reviewed the latest up-to-date published literature on the perioperative outcomes of U-RATS, and where applicable, compared these outcomes to other minimally invasive thoracic surgical procedures such as M-RATS and U-VATS.

Limitations

The study has several limitations. Most of the published studies are retrospective, single-centre, and conducted by a single lead expert surgeon, which may introduce certain biases such as selection bias. Lead expert surgeons performing these procedures typically have extensive experience with multiportal VATS, U-VATS, and RATS, resulting in faster procedure times for U-RATS operations. However, these operative times may not be applicable to surgeons with less experience or those who are early in their U-RATS LC. Furthermore, key comorbidities, such as patients’ past medical history and smoking status, were not detailed in most of the included studies. Margin clearance was also notably unreported. Additionally, the studies primarily focused on short-term perioperative outcomes and did not address long-term clinical and oncological outcomes. They also did not evaluate the cost-effectiveness of U-RATS compared to other established minimally invasive procedures.

Future research

Future research should include more randomized, prospective, multicenter studies involving multiple surgeons and long-term follow-up. These studies should focus on oncological parameters and outcomes, providing a comprehensive evaluation of the U-RATS approach. Additionally, they should compare U-RATS head-to-head with established minimally invasive thoracic techniques such as VATS, U-VATS, and M-RATS.

Conclusions

This review illustrates the security and effectiveness of using the emerging U-RATS technique by skilled surgeons in lung resections. The current publications also highlight the advantages of shorter mean operation time compared to traditional RATS, shorter mean length of hospital stays, and fewer conversion rates to VATS or open surgery, and it can be adopted if a well-experienced and harmonised team is present.

The main drawback is that these studies are retrospective, and report procedures performed mainly by a single surgeon, which makes it difficult to generalise across the thoracic surgery setting. However, as with any emerging technique, randomised, prospective, multicentre, multi-surgeon, long-term follow-up studies with a focus on oncological and clinical will be necessary to report conclusive results of the U-RATS approach, as well as studies comparing it with other established minimally invasive thoracic surgical techniques.

Acknowledgments

Funding: None.

Footnote

Reporting Checklist: The authors have completed the Narrative Review reporting checklist. Available at https://ccts.amegroups.com/article/view/10.21037/ccts-24-26/rc

Peer Review File: Available at https://ccts.amegroups.com/article/view/10.21037/ccts-24-26/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://ccts.amegroups.com/article/view/10.21037/ccts-24-26/coif). D.G.R. serves as an unpaid editorial board member of Current Challenges in Thoracic Surgery from March 2023 to December 2025. 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.

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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