Changes in utilization of robotic bariatric surgery and effect on patient outcomes from 2015–2020

Robotic surgery is an increasingly popular alternative to laparoscopy for performing bariatric operations. To describe changes in utilization and complication rates of this technique over the last six years an analysis of the 2015–2020 Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program participant use files (MBSAQIP PUF) was performed. All patients who underwent laparoscopic or robotic bariatric surgery from 2015 to 2020 were included. 1,341,814 robotic and laparoscopic bariatric operations were included. Both the number and proportion performed robotically increased from 2015 (n = 9866, 5.87%) to 2019 (n = 54,356, 13.16%). In 2020, although the number of cases decreased, the proportion performed robotically still increased (17.37%). Yet, there has been no significant change in 30 day risk of death (p = 0.946) or infection (p = 0.721). In fact, the risk of any complication has decreased from 8.21% in 2015 to 6.43% in 2020 (p = 0.001). Robotic cases are being increasingly performed on high-risk patients with 77.06% of patients being American Society of Anesthesiologists (ASA) class 3 or higher in 2015 versus 81.03% (p = 0.001) in 2020. Robotic cases are also more likely to be revision operations than laparoscopic cases (12.16% vs 11.4%, p = 0.001). From 2015 to 2020 robotic bariatric surgery became more prevalent yet both complication rates and length of operation decreased suggesting it is an increasingly safe option. The risk of robotic complications remains higher than laparoscopy, however there are significant differences in the patient populations suggesting there may be specific patients and/or operations in which robotic bariatric surgery is being used.


Introduction
Obesity is a serious health problem in the United States and the world contributing to many of the leading causes of preventable death [1]. From 2017 to 2020 the prevalence of obesity in the US was 41.9% and obesity related costs were 173 billion dollars in 2019. Bariatric surgery is an effective and durable option for achieving significant weight loss [2]. In 1994 the first laparoscopic gastric bypass was performed by Wittgrove et al. and since then the technique has continued to improve and evolve [3]. The laparoscopic approach to bariatric surgery is now regarded as the gold standard but as robotic surgery has become more prevalent and been increasingly utilized by urology, gynecology, colorectal and general surgery, robotic bariatric surgery has emerged as an alternative. Previous studies have shown that robotic bariatric surgery is increasing in popularity with utilization nearly doubling from 2015 to 2018 [4,5]. As with any new technology a learning curve is expected, and so as utilization increases the data on outcomes is changing and requires re-evaluation. Previous studies have shown improvement over time in robotic outcomes including re-admission, reintervention, leak rates, and overall complication rates [4,5]. However, there are also criticisms of the robotic platform, including increased cost, longer operative times, and lack of clear benefit compared to laparoscopy [5][6][7][8][9]. The data comparing robotic and laparoscopic outcomes in bariatric surgery is heterogeneous with different studies showing increased, decreased and no difference in complication rates between the two modalities [4,8]. This leaves the question of what role robotic surgery should play in bariatric surgery unanswered. This paper represents an updated look at the data through 2020 and includes the largest population studied to date.

Methods
The Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program (MBSAQIP) Participant Use Files (PUF) contain de-identified data on patients undergoing bariatric surgery at over 900 accredited centers across the country. The data collected includes patient demographics, operative details and peri-operative outcomes. Data are collected at participating institutions by a certified clinical reviewer using standardized definitions. Institutional Review Board (IRB) approval was not required for this study as all analyzed data was previously de-identified and entered in a HIPPA compliant manner. We performed a retrospective analysis of this data looking at all patients who underwent laparoscopic or robotic bariatric surgery from 2015 to 2020. This included over 1.3 million operations performed in the US. Data collected for use in this study was patient age, sex, race, pre-op BMI, pre-op diabetes, hypertension, hyperlipidemia, American Society of Anesthesiologists (ASA) class, and operative time. The outcomes studied included mortality within 30 days of operation, length of stay, deep and superficial infection rates, and rates of any complication. This data was collected for each year between 2015 and 2020 and for both laparoscopic and robotic operations. Conversion and revision operations were also included and the incidence of these noted.

Statistical analysis
Statistical analysis was performed using STATA software version 14.2 (StataCorp LLC, College Station, TX). Quantitative variables were reported as means with 95% confidence intervals (CI) and descriptive categorical variables were reported as frequencies and proportions. Univariate analysis using t test or χ 2 test was used to compare demographic, operative characteristics, and postoperative outcomes between groups. Statistical significance was set at p < 0.05.

Results
Between 2015  Outcomes including death during operation or within 30 days, operative length, length of stay, infection, and overall complication rate were also reported for robotic cases each year (Table 3). Over the study period of 2015-2020, as case numbers increased, complication rates decreased. In 2015 the rate of any complication for robotic bariatric surgery was 8.2%. This decreased to 7.2% in 2016, 6.81% in 2017, 7.17% in 2018, 7.06% in 2019, and the lowest rate was in 2020 at 6.43% (p = 0.001) ( Table 3). The peri-operative mortality rate did not significantly change over this time period ranging from 0.07 to 0.11% (p = 0.946). Rate of infection, including superficial and deep space infections, was also stable (p = 0.721, 0.89% in 2020). Both operative length and hospital length of stay significantly decreased from 2015 to 2020. Operative length went from a mean of 128.48 min in 2015 to 118.40 min in 2020 (p = 0.007) and length of stay went from 2 days in 2015 to 1.47 in 2020 (p = 0.007).
Outcomes were also compared between laparoscopic and robotic surgery each year (Table 4). In 2020 operative times for robotic surgery were significantly higher than laparoscopic (118.4 versus 86.76 min, p = 0.001). Risk of complications was also significantly higher for robotic compared to laparoscopic surgery, 6.43% versus 5.55% (p = 0.001). However, there were also important differences in the two patient populations. The proportion of robotic bariatric operations that were revisions was 12.16% in 2020, significantly higher than the percentage of laparoscopic cases (11.4%, p = 0.001). The average BMI (body mass index) was also significantly higher for robotic patients compared to laparoscopic in 2020 (45.14 vs 44.65, p = 0.001).

Discussion
Ultimately, the data show that robotic bariatric surgery is an increasingly safe option. Over our study's time period the utilization of robotic bariatric surgery has more than tripled. In this same time period the rate of complications and hospital length of stay have both significantly decreased. This is even more notable given that over this same time period the patient population has become more high risk. From 2015 to 2020, the average operative time also significantly decreased, suggesting that both surgeons and operating room staff are becoming more familiar with and more adept at robotic surgery. This may be one of the factors contributing to the decrease in complication rates as increased operative time is itself associated with a higher risk of complications in bariatric surgery [7]. The fact that complication rates decreased for this relatively novel surgical approach despite both early and mid-career surgeons newly adopting the technique speaks to another benefit of robotic surgery, that it is widely considered easier to learn than conventional laparoscopy [7,9]. A study by Gray et al. compared outcomes for a first year robotic bariatric attending with two 4-8 year laparoscopic bariatric attendings and found equivalent outcomes [10]. Li et al. performed a meta-analysis, which quantified this difference finding the learning curve for robotic Roux-en-Y Gastric Bypass (RRYGB) to be 10 cases and 20 cases for robotic sleeve gastrectomy (RSG) versus 70-100 for laparoscopy [9]. Robotic surgery has also been widely praised for the ergonomic benefits it offers surgeons and the improved dexterity and visualization compared to conventional laparoscopy. Despite the benefits of robotic surgery, our results showed that laparoscopic bariatric surgery still has a significantly lower risk of complications. That being said, patients undergoing robotic surgery had a higher average BMI and were more likely to have had previous bariatric surgery. Revision bariatric surgery has a higher complication rate than primary surgery and as such this could represent a significant confounding factor [6]. This also suggests that there may be specific high-risk populations in which surgeons are choosing a robotic approach. Previous studies have suggested that the role for robotic bariatric surgery is in complex cases such as revisions or in patients whose anatomy is more challenging, and laparoscopy would be particularly difficult [7]. Studies have specifically compared outcomes for revisional laparoscopic and robotic bariatric surgery but the body of literature is heterogenous. The most recent study was a meta-analysis by Bertoni et al., which looked at 6 studies with a total of 30,000 patients who underwent revision bariatric surgery and they found no difference in complication rates between robotic and laparoscopic approaches [6]. A 2019 review of the MBSAQIP database and its data on revision operations by Nasser et al. found that for patients undergoing revision sleeve gastrectomy a robotic approach was associated with increased operative time, length of stay and increased complication rates [7]. However, in revision roux en Y, robotic surgery had equivalent length of stay, overall morbidity and mortality when compared to laparoscopy. They in fact found a decreased risk of several complications including respiratory complications, SSI (surgical site infection) and bleeding in robotic Roux-en-Y. This shows that there are situations in which robotic bariatric surgery is a better option than laparoscopic. Additionally, in cases where there are no differences in outcomes then the benefits to the surgeon may make the robotic approach superior to conventional laparoscopy.

Limitations of study
Limitations of this study include its retrospective design, although the data has been collected prospectively the analysis is retrospective. Also, as cases are continuously added to the database the data set continues to evolve and studies such as this one require frequent updating as the popularity of robotic surgery and surgeons' skill level continues to improve. In addition, our analysis looked at robotic bariatric surgery as a whole and the trends over the last several years. We did not analyze our outcomes by type of operation or directly compare revision versus primary procedures.

Conclusion
From 2015 to 2020 robotic bariatric surgery became significantly more prevalent yet complication rates, length of hospital stay, and length of operation all significantly decreased showing that robotic bariatric surgery is an increasingly safe option. The data for 2020 show that patients undergoing robotic bariatric surgery tend to be higher risk with higher average BMI and increased rates of prior bariatric surgery compared to laparoscopy. This suggests that surgeons are using the robotic approach not only as a replacement for laparoscopic bariatric surgery but as an alternative option for procedures and patients that would be challenging laparoscopically.
Author contributions All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by AL, MG and EK. The first draft of the manuscript was written by EK and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.
Funding The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.

Data Availability
The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

Conflict of interest
The authors have no relevant financial or non-financial interests to disclose.
Ethical approval This is an observational study, no ethical approval is required.