Introduction

The global adoption of robotic surgery continues to rise in different surgical specialties like colorectal [1,2,3], urology [4, 5], bariatrics [6,7,8], upper gastrointestinal [9,10,11] and gynecology [12,13,14]. While a large proportion of the robotic systems currently installed are the well-established da Vinci robotic surgical system (Intuitive Surgical Inc, California, USA), various manufacturers have developed and introduced alternative robotic systems. A few examples are the Revo-i (Meerecompany, Inc., Seongnam, Republic of Korea) [15, 16], Senhance (formerly ALF-X) (Asensus Surgical, North Carolina, USA) [17, 18], Versius (CMR Surgical, Cambridge, UK) [19], Micro Hand S (Wego, Qingdao, China) [20], Hugo™ RAS (Medtronic, MN, USA) [21, 22], and Hinotori™ surgical robot system (Medicaroid Inc., Kobe, Japan) [23, 24].

Most of these newer robotic surgical systems have been developed with distinctive capabilities such as haptic feedback, modular system, single port operating and implementation of artificial intelligence. In addition, there is also a target for a value-driven healthcare by reducing the device acquisition and ongoing operational cost. These are promising developments especially for ‘robot-naïve’ healthcare systems contemplating to adopt robotic surgical technologies.

Over the last few years, most publications on these novel robotic systems were early model development, preclinical results, feasibility studies and small case series. However, some centers have started publishing their results comparing these novel platforms to conventional laparoscopic approaches and even the da Vinci surgical system.

The aim of this study is to systematically review the existing literature on the clinical outcomes of these newer robotic surgical systems.

Methods

This systematic review of literature and meta-analysis was conducted in accordance to the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines [25]. No ethical approval was required. This systematic review was registered in The International Prospective Register of Systematic Reviews (PROSPERO) with the registration number CRD42023475626.

Electronic search

An electronic search was performed on the following databases: Embase, Medline, Pubmed, Cochrane library and Google Scholar independently by two reviewers on 1st May 2023. The search period was set from year 2012 to May 2023 to identify all published and indexed studies comparing clinical outcomes of newly developed multi-port soft tissue robotic surgical systems against laparoscopic (lap) or da Vinci (DV) robotic approach. A combination of “MeSH” and non- “MeSH” search terms: robotic surgery, robotic console, robotic surgical system, robotic surgical device, laparoscopic surgery, and laparoscopic procedure were used. A manual search of the reference lists of relevant studies was performed to identify additional studies.

Study selection

Two reviewers (Y.L., Z.M.) screened the studies independently to identify articles for potential inclusion. Studies were screened by their titles, abstracts, followed by their full texts. Any conflicts were resolved by consensus.

Studies were considered eligible for inclusion if patients were adult (18 \(\ge \) years old) undergoing robot-assisted soft tissue surgery using newly developed robotic surgical systems with clinical outcomes being compared against laparoscopic or da Vinci robotic approach. Only articles published in English were considered. Studies with insufficient outcome reporting, duplicated data, missing either a laparoscopic arm or da Vinci arm as comparison, case series or reports were excluded.

Data extraction

The primary outcomes of interest were clinical outcomes, including but not limited to the following: surgical complication rate: Clavien–Dindo grading (CD), length of stay (LOS), estimated blood loss (EBL), conversion rate being defined as conversion from the intended robotic approach to any other approaches or a different robotic platform, and standard oncological outcomes in cancer resection studies.

Data were extracted from studies that met the eligibility criteria. Parameters extracted included title, first author, year of publication, country where the study was conducted, study design, number of patients, patient characteristics, type of surgery and outcomes of interest.

Risk of bias assessment

The quality of the included studies was assessed by two reviewers independently using the Newcastle–Ottawa scale (NOS) for non-randomized studies [26] or Jadad scale for randomized control trial (RCT) [27].

Data analysis

Descriptive statistics were used to report patient and outcome data. A meta-analysis was not performed due to the heterogeneity of the procedures and reported clinical outcomes. A systematic narrative review was provided for each outcome.

Results

Literature search

The literature search conducted on the electronic databases revealed 1904 records. Six additional studies were identified from bibliography citation (Fig. 1). After excluding duplicates and records that did not match the main topic, 22 articles were evaluated in full text. Ten articles were excluded as 4 contained overlap data from studies published earlier, 5 articles had no control group, and 1 article did not report clinical outcomes. Twelve studies were included for qualitative analysis [28,29,30,31,32,33,34,35,36,37,38,39].

Fig. 1
figure 1

PRISMA 2020 flow diagram of literature search

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Characteristics and quality of included studies

A total of 1142 patients were presented in the 12 studies with a range between 22 and 168 patients in each study (Table 1). All the studies were published within the last 5 years with 7 studies reported from China and 5 other studies from Croatia, South Korea, Pakistan, India, and Lithuania, respectively. There were 6 newly developed robotic systems being compared in the 12 studies including: Micro Hand S robotic system (Wego, Qingdao, China), Senhance surgical system (Asensus Surgical, NC, United States), Revo-i, model: MSR-5000 (Meerecompany, Inc., Seongnam, Republic of Korea), KangDuo surgical robot (Suzhou KangDuo Robot Co., Ltd., Suzhou, China), Versius robotic surgical system (CMR Surgical, Cambridge, UK), and Hugo™ RAS system (Medtronic, Minneapolis, MN, USA).

Table 1 Characteristics of eligible studies
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There were 2 multi-center RCTs, 5 prospective studies, and 5 retrospective studies. All the non-randomized studies were single-center studies. Wang et al. [30] and Liu et al. [35] both report outcomes of total mesorectal excisions (TME) from the same center with overlap of study period from January 2017 to November 2018 (23 months). However, Liu et al.’s study was a prospective trial with different inclusion criteria. Hence, all patients were assumed to be independent and included. Hussein et al. reported outcomes of a mixture of urology cases following a propensity matched analysis. Therefore, outcomes for each procedural types were extracted and grouped accordingly for qualitative comparison and analysis in this review [33].

All 10 prospective and retrospective studies scored 6 or more on NOS, and therefore were deemed good quality studies [28,29,30,31,32,33,34,35,36, 39]. Two RCTs: Wang et al. [37] and Li et al. [38] scored 3 and 5, respectively, on the Jadad scale indicating moderate and good quality.

Outcomes

Colorectal resections

Four studies reported clinical outcomes on colorectal resections: 1 sigmoid resection, 1 right hemicolectomy, and 2 total mesorectal excision (TME). The studies originated from China and all surgeries were conducted using their locally developed multi-port robotic system: Micro Hand S (MH), (Table 2).

Table 2 Summary findings in colorectal resections
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In the sigmoid resection study, Luo et al. presented their retrospective cohort study of 45 patients (24 DV versus 21 MH) comparing outcomes of 2 different robotic platforms on radical sigmoid colon cancer resection [28]. All patients had histologically confirmed sigmoid colon carcinoma, no distant metastasis and underwent curative resection by experienced surgeons with a primary colorectal anastomosis. Patients with an American Society of Anaesthesiologists (ASA) classification more than 3 were excluded. The patients’ demographics and tumor characteristics were equally matched. There was no difference in short-term outcomes: lymph node yield, EBL, LOS, conversion rate, and moderate to severe post-operative complications (CD Grade ≥ 3) between the DV and the MH group. Operative time and long-term oncological outcomes were not reported.

Zeng et al. reported their outcomes on laparoscopic versus robotic right hemicolectomy using the MH robotic platform [29]. It was a retrospective cohort of 22 patients (12 lap versus 10 MH). All patients had histologically confirmed adenocarcinoma of the right colon, no distant metastasis and underwent elective curative resection by the same surgical team within the study period with pre-operative bowel preparation. The patients’ demographics and tumor characteristics were well matched. The robotic group had a significantly shorter LOS (11.4 ± 3.3 days vs. 15.2 ± 4.7 days, p = 0.046). There was no difference in other short-term outcomes: lymph node yield, EBL, conversion rate and moderate to severe post-operative complications (CD Grade ≥ 3) between the laparoscopic and the MH group.

In terms of rectal resections, Wang et al.’s study [30] retrospectively compared consecutive cases performed by a single surgeon early in the learning curve of both laparoscopic and robotic TME (RTME) using the MH robotic platform. The patients underwent routine investigation for pathological confirmation of rectal carcinoma and staging with both computed tomography (CT) and magnetic resonance imaging (MRI). There were 65 patients in the laparoscopic group versus 40 patients in the MH group. Both groups were evenly matched in general demographics, comorbidity, TNM stage, rate of neoadjuvant chemoradiotherapy (lap 7.7% vs. RTME 12.5%), procedure type (low anterior resection (LAR) and abdominal perineal resection (APR)) and protective ileostomy (lap 51.7% vs. RTME 55%). Clinical outcomes between the 2 groups were not different in terms of completion of TME, lymph node yield, EBL, operative time, LOS, conversions, and post-operative complications (CD Grade ≥ 3).

In contrast, Liu et al. [35] conducted a prospective trial comparing outcomes of 3 different minimally invasive approaches: lap, DV and MH in TME. This was not a randomized trial as patients were free to select their method of surgical resection albeit performed by the same surgeon. The number of patients were similar in all groups. No significant differences were found in general demographics, comorbidity, TNM stage, rate of neoadjuvant chemoradiotherapy and diverting stoma rate. In comparison between the laparoscopic group, DV and MH groups, the laparoscopic group had a higher rate of Hartmann’s (6.7% vs. 0%, 0%, p = 0.033) and APR (13.3% vs. 4.3%, 2.3%, p = 0.035), higher volume of blood loss [95.1 ± 78.9 ml vs. 65.4 ± 35.8 ml (p = 0.037), 66.6 ± 35.2 ml (p = 0.041)], lower lymph node yield [15 ± 4.2 vs. 17.5 ± 4.6 (p = 0.0310), 17.3 ± 4.1 (p = 0.033)], higher rate of conversion to open [6.8% vs. 2.2% (p = 0.038), 2.3% (p = 0.04)], and higher rate of severe complications, in particular anastomotic leak [13.9% vs. 4.4% (p = 0.023), 2.3% (p = 0.031)]. Operative time in the lap group was shorter than the robotic groups, DV and MH [205.5 ± 85 min vs. 230.1 ± 75.5 min (p = 0.043), 235 ± 70.5 min (p = 0.045)].

Radical prostatectomy

Three studies reported clinical outcomes on radical prostatectomy [31, 34, 39] (Table 3). All 3 studies compared different robotic platforms. Kulis et al. [34] conducted a prospective study comparing the Senhance robotic system (n = 107) to laparoscopic group (n = 61). Two operating surgeons with limited laparoscopic and robotic radical prostatectomy experience (< 20 cases as primary surgeon) conducted the procedures. The demographics and clinical stage of the prostate tumor were matched. The laparoscopic group was associated with a higher EBL and LOS with no differences in positive surgical margins and post-operative complications (CD Grade ≥ 3). The conversion rate in the Senhance group was significantly higher (8.7% vs. 0%) due to robotic platform issue and anatomical constraints.

Table 3 Summary findings in urological procedures
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Alip et al. [31] published their outcomes of radical prostatectomy in South Korea comparing 2 robotic platforms: DV versus Revo-i developed in South Korea. All surgeries were performed by an experienced robotic surgeon who had performed more than 1000 robotic prostatectomies using the DV platform. A 1:1 propensity score matching analysis was performed using the following co-variates: age, ASA score, body mass index (BMI), previous abdominal and endoscopic surgery, pre-operative prostate specific antigen (PSA), prostate volume, International Society of Urological Pathology (ISUP) grade group, tumor stage, and need for pelvic lymphadenectomy resulting in 33 patients in each group. The Revo-i group had a significant longer operative time (126.2 ± 55.2 min vs. 92.4 ± 26.1 min, p < 0.01) but shorter LOS (5 ± 1.9 days vs. 5.8 ± 2.2 days, p = 0.036) compared to the DV group. There was no difference in EBL, surgical complications, and surgical margins.

Ragavan et al. [39] published their series of 17 patients who underwent robotic radical prostatectomy with the new Hugo™ RAS system (Hugo) platform. Seventeen matching patients who underwent robotic radical prostatectomy using the DV platform were selected from their database as controls for comparison. Demographics, pre-operative PSA, and tumor stage were evenly matched. A shorter operative time was noted in the Hugo™ group (153.8 ± 24.3 min vs. 165 ± 12.1 min). No differences in surgical complications, surgical margins, or conversion to open were detected.

Pyeloplasty

Two studies published outcomes on pyeloplasty [32, 33] (Table 3). Fan et al. [32] reported their early outcomes of 16 patients operated on a newly developed robotic platform: KangDuo (KD) surgical robot versus 16 patients on the established Dd Vinci robotic platform. The 2 groups were evenly matched in terms of demographics, BMI, comorbidity, pathology, and anatomy. There were no differences in operative time, EBL, LOS, success rate and complication rate between the 2 groups. Similarly, Hussein et al. [33] described their early experience and outcomes with the Versius robotic system in comparison to the more established DV system in their center. Patients in the DV group were matched to the same proceduralist performing the same operation on 2 different platforms. There were 25 patients in the DV group and 9 in the Versius group with slightly better outcomes in the DV group in operative time, EBL and LOS.

Partial nephrectomy

Two studies published outcomes on partial nephrectomy [33, 38] (Table 3). Li et al. [38] conducted a double-center RCT comparing outcomes of partial nephrectomy in patients with T1aN0M0 renal carcinoma between KD and DV. 50 patients were recruited into each group but 1 patient in the KD group did not undergo the procedure due to an equipment sterilization issue. Both groups were well matched in terms of age, BMI, pathology, and anatomical factors. Although the total operative time was similar between the 2 groups, the robot-docking time and suture time per stitch were significantly longer in the KD group (4.26 ± 1.69 min vs. 3.44 ± 1.26 min, p = 0.015), (48 ± 15 s vs. 31 ± 7 s, p = 0.000). No difference was reported in conversion, warm ischemia time, success rate, EBL, LOS and renal function up to 12 weeks post operatively between the 2 groups.

Hussein et al. [33] in their early outcomes only reported a very small series of DV (n = 4) versus Versius (n = 6) of partial nephrectomy. Versius had a shorter total operative time, EBL and conversion rate. No data were reported for post-operative complications and LOS.

Cholecystectomy

There were 2 studies which published their outcomes on cholecystectomy: 1 multi-center RCT [37] and 1 retrospective propensity score matched analysis [36] (Table 4). Wang et al. [37] conducted a single-blinded multi-center RCT comparing early surgical outcomes of cholecystectomy performed using the DV versus the MH platform. The study had strict selection criteria and only recruited patients with benign cholelithiasis, non-inflamed gallbladder, were relatively well with low ASA scores and minimal comorbidities. All surgeons within each center were skilled surgeons in robotic cholecystectomy. There were 84 patients in each group. The mean age in the MH group was younger (45.2 ± 10.8 years vs. 48.8 ± 10.7 years, p = 0.028). The MH group had a lower robot-docking time (12 ± 10.5 min vs. 16.4 ± 13.9 min, p = 0.025) with no difference in console time. Breach of gall bladder was significantly higher in the DV group (15.7% vs. 4.8%, p = 0.021). No difference was noted in success rate, LOS, and post-operative complication rate.

Table 4 Summary findings in cholecystectomy
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Samalavicius et al. [36] compared early outcomes of Senhance robotic cholecystectomy against a matching number of laparoscopic cholecystectomies within the same institution (n = 20). The operative time in the robotic group was significantly higher (88.5 ± 24.5 min vs. 60.8 ± 16.7 min, p = 0.001). No difference in EBL, LOS, and post-operative complications were detected in this small cohort study.

Discussion

This systematic review examined 12 trials comprising of 1142 patients with the aim of evaluating the clinical outcomes of newly established multi-port robotic surgical systems. All studies included in this review were published in the last 3 years arising from Asia and Europe encompassing colorectal, urology and biliary procedures. Eight studies were head-to-head comparisons of novel robotic platforms: Micro Hand S, Senhance, Hugo™ RAS, and KangDuo robotic systems against the da Vinci robotic platform. The outcomes between the novel robotic systems and Da Vinci robotic system were comparable. Three studies comparing the conventional laparoscopic approach with the robotic group demonstrated longer operative time [35, 36] and lower EBL [28, 34, 35] in the robotic group.

All 8 direct comparison studies between robotic platforms included in this review showed little difference in surgical outcomes in sigmoid colectomies, rectal resections, prostatectomy, pyeloplasty, partial nephrectomy and cholecystectomy. The newly developed robotic platforms had achieved a high level of technical capabilities and mechanical precision. This is especially true in procedures which rely on superior technical execution such as the TME studies showing > 70% of complete TME [30, 35] and comparable clear resection margins in radical prostatectomy [31, 39]. However, most of the studies consisted of carefully selected patient cohorts with low BMI, minimal comorbidities, and ASA scores less than 3. Therefore, the results may not be readily applicable to the general cohort of patients with high BMI or complex pathologies. These difficult surgical circumstances can be very challenging with conventional laparoscopic techniques even for experienced surgeons and may theoretically benefit from the superior ergonomics of robotic platforms.

Unsurprisingly, when compared against conventional laparoscopic approaches, the novel robotic systems (Senhance and Micro Hand S) showed longer operative time and lower blood loss volume. The longer operative time ranged from mean increase of 3 min to 30 min [30, 34,35,36]. Interestingly, Kulis et al. reported a longer operative time in the first 30 cases and subsequently became shorter than the robotic group in the last 31 cases likely reflective of a steeper learning curve associated with the Senhance robotic platform consistent with a significantly higher conversion rate in the robotic group which the author attributed to the early learning curve [34].

Longer operative time has been a point of contention against robotic surgery. The length of the surgical procedure is intricately related to the learning curve when adopting a new technique. Our review demonstrated a shorter operative time with the established laparoscopic and the da Vinci robotic platforms most likely due to the surgeons’ progression beyond the learning curve with standard laparoscopic tools and the da Vinci robotic platform. Hence, as the proceduralist obtains more experience with these emerging robotic platforms and progresses beyond the learning curve, operative time should decrease over time. One study suggested a 43-min reduction in operating time after 43 cases of robotic rectal surgery [40] and Shaw et al. found a reduction in mean operating time of 53 min in robotic colorectal procedures after 15 cases, despite an increase in case complexity [41]. Looking beyond the additional minutes spent in theater, proponents of robotic surgery would argue on the point of reduced days of hospital stay. For example, Wang et al. [30] reported a mean reduction of 2.7 days in robotic TME versus laparoscopic TME. Similarly, Tewari et al.’s meta-analysis showed a mean reduction of 2.3 days in robotic versus laparoscopic prostatectomy [42].

While this review was aimed to review literature over the last 10 years, all included articles were published within the last 3 years. This indicated that all the novel robotic systems were in a similar phase of clinical development likely secondary to the lapse of several key patents in 2019 owned by Intuitive Surgical Inc. which allowed other manufacturers to introduce their new robotic systems [43]. Each new systems has been designed with different notable features (Tables 5, 6) to overcome the technical or cost constraints of the robotic platform. Furthermore, these are first generation and therefore further improvement, and optimization is expected. On the other hand, da Vinci had introduced 4 generations of their robotic system (2000/S/Si/Xi) with robust clinical data especially in the field of urology [44].

Table 5 Comparison of different robotic systems
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Table 6 Illustrations of the various robotic platforms
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Currently, the cost of robotic surgery remains a major barrier to widespread implementation [45,46,47], particularly in low and middle income countries even though the disease burden in these countries is significantly higher [48]. As a result, many countries such as China, Japan and Korea have developed their own robotic systems with the aim of improving cost-effectiveness. Only one study compared the hospital cost of the MH system to the DV system in sigmoid colectomy which accounted to 23.6% savings on the MH system. Other studies such as Alip et al. [31] predicted a 42% reduction of cost using the Revo-i robotic system for radical prostatectomy and Wang et al. [37] predicted a 75% reduction in cost using MH system for simple cholecystectomy. The achieved savings without compromising clinical outcomes are promising but must be interpreted with caution as these figures were not validated externally.

In addition to cost, another barrier to clinical implementation is robotic training. The learning curve for each system will be variable. Most of the procedures in this review were performed by the same group of surgeons on 2 different platforms suggesting the feasibility of skill transfer between robotic platforms. This concept has yet to be proven in clinical studies. A successful crossover of skills across different robotic platforms would open the possibility of health systems acquiring different robotic platforms to suit specific clinical circumstances without the need to retrain their robotic surgeons.

In this study, we focused our systematic review on novel multi-port soft tissue robotic systems with published comparison data to demonstrate the safe implementation and efficacy of these systems. Other emerging multi-port robotic systems with early clinical data did not fit our review criteria but possessed great potential due to their distinct design elements. SSI Mantra™ (Sudhir Srivastava Innovations Pvt. Ltd, Haryana, India) design featured a modular system with cardiac surgery specific instruments. Switzerland designed and manufactured Dexter robotic system (Distalmotion, Epalinges, Switzerland) used a modular platform and instruments compatible with standard laparoscopic ports. This facilitates seamless transition between laparoscopic and robotic approaches and extended the application of robotic surgery into the ‘hybrid realm’. Hinotori™ surgical robot system (Medicaroid Inc., Kobe, Japan) was designed with a compact operation arm that couples eight axes of motion to reduce interference between the robotic arms and bedside surgeon. Avatera robotic system (Avateramedical GmbH, Jena, Germany) featured a thin space-saving patient cart, equipped with disposable 5 mm robotic instruments. This eliminated the need for costly sterilization.

Other robotic systems such as the da Vinci’s single port robotic system which utilized a single surgical entry site and Endoquest robotic system (Endoquest Robotics, Houston, Texas, US) to conduct endoluminal procedures (i.e., submucosal dissection, endoscopic mucosal dissection) were beyond the scope of this review.

The main limitation of this review was the lack of data from RCTs. Most of the studies were retrospective case series. The retrospective nature of the studies would have inevitably introduced selection bias in our analysis with surgeons selecting surgical approaches most suitable for their skillset and robotic platform. The 2 RCTs compared patients with low ASA scores, low comorbidity state, and low BMI which limited the application in the obese and elderly population with higher burden of diseases.

Conclusion

This systematic review highlighted the safe implementation and efficacy of 6 new robotic systems. The clinical outcomes achieved by these new robotic systems were comparable to the established da Vinci robotic system in selected cases. There is emerging evidence that these new robotic systems are reliable and present an alternative to the current available robotic platforms.