A comparison between the da Vinci Xi EndoWrist Stapler and a conventional laparoscopic stapler in rectal transection: A randomized controlled trial

Distal rectal transection following robotic total mesorectal excision for rectal cancer is challenging. This can be performed with either a robotic stapler (RS) or laparoscopic stapler (LS). We compared the operative outcomes and ergonomic differences between RS and LS.


| INTRODUCTION
Since it was first described in 2006, 1 robotic total mesorectal excision (TME) has gained widespread adoption and acceptance. Robotic surgery achieves at least similar oncological outcomes to laparoscopic surgery, 2 while providing improved ergonomics during rectal dissection. 3 However, after mobilising the rectum, the robotic surgeon still needs to complete the distal rectal transection, which can be performed either transabdominally using a robotic stapler (RS) or conventional laparoscopic stapler (LS), or transanally.
The use of LS in a deep and narrow pelvis can be technically challenging due to the limited articulation and maneuverability of these devices. This can result in a greater number of stapler cartridges required to complete the rectal transection, contributing to an increased risk of anastomotic dehiscence. 4 In contrast, the da Vinci Xi EndoWrist Stapler (Intuitive Surgical Inc.) touts a wider range of articulation and more ergonomic surgeon control that potentially allows for improved stapler engagement and ease of use. [5][6][7] Studies have shown that the RS is safe, simplifies rectal transection, reduces the average number of stapler firings, and therefore potentially decreases the incidence of anastomotic leakage. 5,7 These studies are however retrospective in nature and are prone to bias.
The aim of this randomized controlled trial was to compare the operative outcomes and ergonomic differences between the use of RS and LS after robotic rectal dissection.

| MATERIALS AND METHODS
A single centre prospective, parallel group randomized controlled trial was conducted between March 2018 and July 2022. The inclusion criteria consisted of (1) patients aged 18 or older, (2) with a histological ligation of the inferior mesenteric artery and complete mobilisation of the left colon, followed by (4) rectal dissection, and finally (5) rectal transection with the assigned stapler device. If the patient was assigned to LS, a 45 mm LS (Powered Echelon FLEX™ Endopath®, Ethicon) was introduced either through the 12 mm robotic port in the right iliac fossa or the 12 mm suprapubic port, whichever was more ergonomic to complete the rectal division. For the RS group, a 45 mm RS (EndoWrist Stapler, Intuitive Surgical) was inserted through the 12 mm R3 robotic port and rectal transection was performed by the Lead Surgeon using the robotic console. To ensure technical proficiency, the operator of either stapling device was required to have performed at least 50 successful fires of the stapler in live cases before being allowed to participate in the study. This was in addition to the minimum case experience of 50 robotic surgeries. Bowel perfusion was confirmed with Firefly-ICG fluorescence imaging, and a circular stapler was used to complete the colorectal or coloanal anastomosis. An on-table flexible sigmoidoscopy was performed post-anastomosis to evaluate the staple line integrity (intact and complete staple line with no air leak) and perfusion (no mucosal colour demarcation and no staple line bleeding). Defunctioning stomas were fashioned for all patients who had undergone neoadjuvant radiotherapy and/or those who had coloanal anastomoses.
Postoperatively, all patients were placed on an Enhanced Recovery pathway. Patients were discharged when they were able to tolerate oral intake and achieve their pre-morbid ambulatory status.
Surveillance was performed in accordance with National Comprehensive Cancer Network (NCCN) guidelines. 8 Patient demographics and operative variables were recorded in a predefined database. Pelvimetric parameters-pelvic inlet, interspinous distance, pelvic outlet-were measured using preoperative CT Anastomotic defects, if any, were also documented.
Data was collected prospectively and recorded on a data collection sheet which was then uploaded onto an institution REDCap database.
Quantitative data was presented as mean (standard deviation) or median (interquartile range) and was analysed using the student's ttest or the Mann Whitney U test. Qualitative data was presented in absolute numbers or proportions and analysed using the χ 2 test or Fisher's exact test. We used an intention to treat principle for all analyses. A p value of less than 0.05 was taken to be significant. All statistical analyses were performed using the SPSS 16.0 (IBM Corp.). Most of the patients were male (63%), with a median age of 65 (57-75.8), and a mean BMI of 24.0 (5.1). Baseline characteristics were similar between both groups except for the RS group having a smaller mean pelvic inlet diameter of 11.7 (0.9) cm versus 12.6 (1.6) cm, p = 0.038. There was no significant difference in tumour characteristics in terms of location, T-stage and size (Table 1).   Results from the user experience survey (   Similarly, Tejedor and colleagues reported that transection of the rectum using one or two firings was achieved in a higher proportion of RS cases (91%) compared with LS cases (60%; p < 0.001) and concluded that rectal division with RS requires fewer stapler firings, with a potential reduction in the incidence of anastomotic leakage. 7 While retrospective analysis of rectal resections performed in our institution previously also suggested a possible reduction in the number of stapler fires required for rectal transection using RS, the current prospective randomized trial did not show this to be statistically significant. This could be partly explained by the inclusion of rectal transections that were performed above the peritoneal reflection. At this level, the relative dimensions of the bony pelvis and the stapler did not result in much difficulty during rectal transection -the majority (90%) of HIGH transections were either 'very easy' or 'easy' to perform, regardless of which stapler was used. When RS was used in this group of patients, the overall ease of staple transection was 'very easy' in all cases. In comparison, half of the LS transections amongst the LOW cases were completed with difficulty. In addition, the RS was credited for 90% of the LOW transections that were 'very easy' to perform. Subgroup analyses of LOW cases did not show any statistically significant difference for number of stapler cartridges, adjustments and time required to complete the rectal transection, but this was likely due to the limited sample size.

Between
Although there was a trend towards a reduction in the number of stapler cartridges in firings that were easier to perform, this was not T A B L E 2 Operative and post-operative outcomes.  In terms of the safety profile of the staplers studied, our results showed no significant material difference. All staple lines were wellformed with satisfactory levels of haemostasis. Cases of mucosal bleeding were possibly reflective of the circular staple line instead of the linear staplers that were being studied, and the incidence was too low to perform meaningful analysis on the possible effects of crossstapling. There was also no difference in the anastomotic leak rate between both staplers. We did not routinely collect bowel functional outcome data for cases of HIGH rectal transection, but there was no difference in the low anterior resection syndrome score between RS and LS for the patients in the LOW group.
In a bid to standardise the length of the staplers used in this

| CONCLUSION
The Endowrist stapler required less adjustments and resulted in a