A Comparison between the da Vinci Xi Endowrist Stapler and a conventional Laparoscopic Stapler in Rectal Transection: A Randomized Controlled Trial

doi:10.21203/rs.3.rs-2071813/v1

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Research Article

A Comparison between the da Vinci Xi Endowrist Stapler and a conventional Laparoscopic Stapler in Rectal Transection: A Randomized Controlled Trial

https://doi.org/10.21203/rs.3.rs-2071813/v1

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PURPOSE

Distal rectal transection following robotic total mesorectal excision (TME) for rectal cancer can be challenging especially in the deep and narrow pelvis. This can be performed transabdominally using either a robotic stapler (RS) or laparoscopic stapler (LS). We compared the operative outcomes and ergonomic differences between RS and LS after robotic TME.

METHODS

We performed a single center randomized controlled trial. 40 patients with rectal or rectosigmoid cancer who were planned for elective robotic rectal surgery were randomized to either RS (N = 20) or LS (n = 20). Primary outcome was the number of stapler cartridges required to completely transect the rectum. Secondary end points included technical ease and efficacy of stapler use, completeness of the staple line, staple line bleeds, and clinically significant anastomotic leaks.

RESULTS

The mean number of stapler cartridges expended was similar between RS and LS (1.75 versus 2.05, p=0.082). While significantly less stapler adjustments were required in the RS group (1.55 versus 2.75, p = 0.014), complete rectal transection took a comparable amount of time (p=0.149). There were no differences in integrity of staple line, staple line bleeding and anastomotic leaks. Results from the user experience survey showed that RS scored better for control, engagement, visualization and overall experience. Experience with firing and disengagement was similar between both groups.

CONCLUSION

The RS was more ergonomic than the LS. While this complemented the use of robotics in rectal surgery, it did not result in a significant reduction in the number of stapler cartridges required for rectal transection.

Minimally invasive surgery

colorectal

surgical stapler

robotic stapler

stapler firings

Since it was first described in 2006 [1], robotic total mesorectal excision (TME) has gain 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 mobilizing 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 being 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., Sunnyvale, CA, USA) touts a wider range of articulation and more ergonomic surgeon control that potentially allows for improved stapler engagement and therefore reduced number of stapler cartridges required to complete the distal rectal transection [5 – 7].

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.

Patients

A single center 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 diagnosis of rectal or rectosigmoid adenocarcinoma, (3) who were planned for elective robotic rectal surgery. The following patients were excluded: those who were planned for (1) an abdominoperineal resection, (2) transanal rectal transection, (3) multivisceral resections that required the use of additional endoscopic staplers, and (4) patients who declined randomized allocation. All patients were preoperatively staged with a computed tomography (CT) scan of the chest, abdomen, and pelvis. Magnetic resonance imaging (MRI) scan was also performed for all patients with rectal cancer. Neoadjuvant and adjuvant therapies proceeded as recommended by a multidisciplinary tumour board, unaffected by the participation in this trial. The study was approved by the Singhealth Institutional Review Board and informed consent was obtained from all patients. Research data was maintained in accordance with national privacy laws.

Randomization and blinding

Eligible patients were randomly assigned on a 1:1 basis to undergo distal rectal transection using either a LS or RS according to a computer-generated random sequence which was kept concealed by an independent clinical trial coordinator. Taking into consideration that a lower rectal transection would be more difficult, patients were stratified according to the level of transection – above (HIGH) or below (LOW) the peritoneal reflection. The assignments were contained in sealed envelopes and were only revealed after the surgeon had completed the rectal dissection and was ready to perform distal transection of the rectum. The surgeons and trial coordinators were not blinded and only the patients were masked to the assigned stapler group.

Surgical procedure and follow-up

All patients underwent robotic surgery using the da Vinci® Xi surgical system (Intuitive Surgical Inc., Sunnyvale, CA, USA). After general anesthesia, patients were placed in a Lloyd-Davies position with Trendelenburg and right tilt. Following initial pneumoperitoneum, three 8mm robotic ports and one 12mm robotic port were placed along an offset costo-femoral line 6-8cm apart from each other. The 12mm port was placed in the right iliac fossa as the R3 robotic stapler port. Another 12mm port was placed in the midline suprapubic region – this incision would later be incorporated into the Pfannenstiel extraction site. Apart from acting as a vent for surgical plume, this suprapubic port also served as an alternative access site for the LS. Either a 5 or 12mm port was inserted at the right hypochondrium for use by the bedside assistant (Figure 1).

All surgeries were completed in a single docking, with complete mobilization of the splenic flexure. The procedural steps were standardized in the following manner: (1) medial to lateral mobilization and ligation of the inferior mesenteric vein at the inferior border of pancreas, (2) complete mobilization of the splenic flexure and dissection of the mesocolon off the pancreas, (3) high ligation of the inferior mesenteric artery and complete mobilization 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 45mm LS (Powered Echelon FLEX™ Endopath®, Ethicon) was introduced either through the 12mm robotic port in the right iliac fossa or the 12mm suprapubic port, whichever was more ergonomic to complete the rectal division. In cases where another specialist Colorectal surgeon was not available as the bedside assistant, the robot would be completely undocked and the staple transection would be performed by the Lead Surgeon, aided by laparoscopic retraction. If an experienced bedside assistant was present, then the Lead Surgeon would continue controlling the robotic instruments to provide retraction and exposure during the stapling process, undocking only the R3 port to allow insertion of the LS. For the RS group, a 45mm RS (EndoWrist Stapler, Intuitive Surgical) was inserted through the 12mm R3 robotic port and rectal transection was performed by the Lead Surgeon using the robotic console. Green color stapler cartridges were used for all cases. 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. After dividing the proximal mesenteric margin intracorporeally, bowel perfusion was evaluated using Firefly-ICG fluorescence imaging before exteriorizing the transected rectum through a wound protector. The specimen was removed, and the circular stapler anvil was inserted before returning the bowel to the peritoneal cavity for a colorectal or coloanal anastomosis under laparoscopic guidance. 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 color 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 where enteral intake was allowed immediately, and early ambulation was facilitated by the ward physiotherapist. Patients were discharged when they were able to tolerate oral intake and achieve their pre-morbid ambulatory status. The first follow-up visit was within 2 weeks of discharge, then every 3 months for the first 2 years, and 6 months subsequently for a total of 5 years. Surveillance was performed in accordance with National Comprehensive Cancer Network (NCCN) guidelines, including clinical assessment, serum carcinoembryonic antigen (CEA), colonoscopy and CT scans of the chest, abdomen, and pelvis [8].

Outcomes

Patient demographics and operative variables were recorded in a predefined database. Pelvimetric parameters – pelvic inlet, interspinous distance, pelvic outlet – were measured using preoperative CT imaging.

The primary end point was the number of stapler cartridges required to completely transect the rectum. Secondary end points included (1) technical ease and efficacy of stapler use, (2) the completeness of the staple line, (3) staple line bleeds, and (4) clinically significant anastomotic leaks. Technical evaluation of the stapler included (1) the number of times the stapler had to be readjusted, defined as the number of times the operator had to release the rectum after having completely clamped it with the stapler, (2) total time required to complete the rectal transection, defined as the time the stapler was first inserted till the rectum was completely divided, and (3) the subjective ease of performing the transection based on a 5-point Likert questionnaire evaluating the following components of the stapling process: (1) control of stapler, (2) engagement of the rectum with the stapler, (3) visualization of the stapler, (4) firing of the stapler, (5) disengagement and retrieval of stapler and (6) overall experience (Appendix 1). A score of 1 was given if the operator found it very easy and 5 if it was very difficult. The staple line was visually inspected for completeness, and whether there were any staple malformations or areas of dehiscence. The assessment of active staple line bleeding was performed using the da Vinci endoscope for the serosal surface, and a flexible sigmoidoscope for the intraluminal aspect. Any interventions required to secure hemostasis were documented.

Statistical Analysis

To achieve a power of 80% with a 95% confidence interval, assuming a reduction in stapler cartridges from two in the LS group to one in the RS group based on retrospective analysis of our institution case series, the estimated sample size required would be 16 in each arm. Buffering for a 20% drop out rate, we recruited 20 patients into each group.

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 t-test or the Mann Whitney U test. Qualitative data was presented in absolute numbers or proportions and analysed using the χ² 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., Armonk, NY, USA)

Between March 2018 and July 2022, a total of 79 patients were planned for robotic surgery after being diagnosed with rectosigmoid and rectal cancer. Thirty-nine patients were excluded for the following reasons: planned abdominoperineal resection (n=6), planned transanal distal transection (n=6), multivisceral resections (n=7), and declined participation (n=20). The remaining 40 patients who fulfilled our study criteria were randomized into LS (n =20) and RS (n=20). All surgeries were completed robotically with no conversions. Transanal intersphincteric dissection was performed for one patient in the LS group after rectal transection to secure a more definite distal margin. See Figure 2. For the consort flow diagram.

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. The was no significant difference in tumor characteristics in terms of location, T-stage and size (Table 1).

Operative and postoperative outcomes are summarized in Table 2. The mean number of stapler cartridges expended was slightly lower in the RS group (1.75 versus 2.05, p=0.082) but this did not reach statistical significance. While significantly less stapler adjustments were required in the RS group (1.55 versus 2.75, p = 0.014), complete rectal transection took a comparable amount of time (p=0.149).

Staple lines were well-formed in all patients and there was no significant difference in hemostasis. There were two cases of anastomotic leaks in the LS group – one patient underwent surgery to repair the anastomosis, with a defunctioning stoma created; the other patient, who already had an ileostomy from the index surgery, was successfully managed with image-guided percutaneous drainage. One patient from the RS group underwent refashioning of the anastomosis with defunctioning stoma creation for the same reason. There were no other significant (Clavien-Dindo grade 3 or above) 30-day morbidities, and there were no mortalities in either group.

R0 resection was achieved for all cases and there was no significant difference in distal margin between the groups (p=0.583).

Results from the user experience survey (Table 3) showed that the RS scored better for control, engagement, visualization and overall experience. Experience with firing and disengagement was similar between both groups.

Table 1 Patient characteristics

Characteristic

(n = 20)

p value

Age, years ^a

67 (57-77)

64.5 (57 – 74.5)

0.635

Gender ^c

• Male

• Female

11 (55%)

9 (45%)

14 (70%)

6 (30%)

0.514

BMI (kg/m²) ^b

ASA classification ^c

• 1
• 2
• 3

ECOG classification ^c

• 0
• 1
• 2

Tumour location ^c

• Rectosigmoid
• Rectum

T stage ^c

• T1
• T2
• T3
• T4

Tumour size ^b

Pelvimetry ^b

• Inlet diameter (cm)
• Interspinous distance (cm)
• Outlet diameter (cm)

Neoadjuvant chemotherapy ^c

• No
• Yes

Neoadjuvant radiotherapy ^c

• No
• Yes

23.9 (5.1)

5 (25%)

12 (60%)

3 (15%)

9 (45%)

10 (50%)

1 (5%)

10 (50%)

5 (25%)

3 (15%)

8 (40%)

4 (20%)

3.9 (2.3)

12.6 (1.6)

10.9 (1.5)

9.6 (1.9)

17 (85%)

3 (15%)

15 (75%)

5 (25%)

24.1 (5.4)

5 (25%)

10 (50%)

5 (25%)

12 ((60%)

8 (40%)

9 (45%)

11 (55%)

6 (30%)

2 (10%)

9 (45%)

3 (15%)

3.8 (1.9)

11.7 (0.9)

10.2 (1.1)

8.6 (1.5)

18 (90%)

2 (10%)

18 (90%)

2 (10%)

0.947

0.772

0.527

0.5

0.911

0.038

0.108

0.058

0.407

^aData is presented as median (IQR); ^b Data is presented as mean (standard deviation); ^c Data is presented as number (%).

Table 2 Operative and Post-operative outcomes

Characteristic

(n = 20)

p value

Number of stapler cartridges required ^b

Number of stapler adjustments required ^b

Time taken to complete rectal transection (s) ^a

Staple complete ^c

• No
• Yes

Serosal bleed ^c

• No
• Yes

Mucosal bleed ^c

• No
• Yes

Anastomotic leak ^c

• No
• Yes

Distal margin (cm)

2.05 (0.51)

2.75 (1.65)

408.5 (279 – 553.8)

20 (100%)

19 (95%)

1 (5%)

19 (95%)

1 (5%)

18 (90%)

2 (10%)

4.17 (2.17)

1.75 (0.55)

1.55 (1.28)

361 (259.8 – 419.8)

20 (100%)

17 (85%)

3 (15%)

19 (95%)

1 (5%)

3.75 (2.59)

0.082

0.014

0.149

0.605

0.583

^aData is presented as median (IQR); ^b Data is presented as mean (standard deviation); ^c Data is presented as number (%).

Table 3 Mean user experience Likert score

Characteristic

(n = 20)

p value

Control ^b

Engagement ^b

Visualization ^b

Firing ^b

Disengagement ^b

Overall ^b

2.9 (0.9)

2.3 (1.2)

2.2 (1.2)

1.2 (0.5)

1.2 (0.4)

2.2 (0.8)

1 (0)

1.3 (0.6)

1.4 (0.7)

1 (0)

1.1 (0.2)

<0.01

0.003

0.018

0.487

0.231

<0.001

^b Data is presented as mean (standard deviation)

Apart from the technical demands of mesorectal excision, another challenge in rectal cancer surgery is the distal transection of the rectum. This is most appreciable in the patient with a deep and narrow pelvis, who also has a bulky rectal tumor or mesorectum. The ideal stapler for rectal transection should have (1) a compact profile that allows it to be passed beyond a bulky rectum, and perhaps even conform to the limited confines of the bony pelvis, (2) a wide enough stapler opening span to accommodate the target tissue between its jaws, (3) the ability to angulate and articulate ergonomically so that it engages the rectal axis perpendicularly, (4) a variable staple height or compression that accounts for the thickness and pliability of the rectum, especially in cases that have undergone neoadjuvant radiotherapy, and (5) a reliable staple deployment that securely seals the remnant stump with adequate hemostasis without compromising on anastomotic perfusion. Despite the advances in laparoscopic stapler technology, most devices are still hamstrung by limitations in the range of stapler jaw movement and the physical bulk of their rigid shafts. This is compounded by the suboptimal instrument trajectory from laparoscopic ports that are sited to accommodate intraperitoneal dissection instead of distal rectal transection.

The EndoWrist Stapler, on the other hand, has a 108-degree cone of wristed articulation. It also incorporates SMARTCLAMP technology, which indicates if the appropriate cartridge has been chosen for the tissue that the stapler has been applied to. In addition, by telemanipulating the EndoWrist Stapler from the surgeon console, the Lead Surgeon can maintain simultaneous control of the endoscope and retracting robotic instruments.

While retrospective analysis of rectal resections performed in our institution previously 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 resection. 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.

Although there was a trend towards a reduction in the number of stapler cartridges in firings that were easier to perform, this was not statistically significant. In this study, only Colorectal Specialists were involved in the rectal transection to avoid confounding by the learning curve of operating the stapler, especially in the challenging confines of the pelvis. This could account for the majority (90%) of transections being completed in two or less fires of the stapler. Notwithstanding, transections that required more than two stapler firings were predominantly seen in the LS group (75%).

The Likert scores for rectal transection using the RS were significantly better in terms of stapler control, engagement of the rectum, and visualization of this process within the pelvis. Coupled with the ergonomic advantages of the RS, this resulted in a significantly better user experience during rectal transection (p<0.001). The ease of stapler engagement resulted in a reduction in the number of readjustments that were required before final transection (p=0.014), but this benefit did not translate to a significant reduction in transection time (p=0.149). The authors postulate that this might be due to the additional amount of time that was required to undock the RS from the instrument carriage of the robot arm, reload the stapler cartridge, and subsequently redock and reintroduce it to the operative field. The ability of the Lead Surgeon to control the endoscope and robotic retracting instruments provided greater autonomy and coordination of tissue manipulation during the introduction of the RS into the pelvis. In the LS group, the Lead Surgeon must either forego his controls at the surgeon console and operate the LS personally, or he must depend on an experienced bedside assistant to perform this task.

In terms of the safety profile of the staplers studied, our results showed no significant material difference. All staple lines were well-formed with satisfactory levels of hemostasis. 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 cross-stapling.

In a bid to standardize the length of the staplers used in this study, only 45mm cartridges were used. The authors acknowledge that there might have been instances where a 60mm stapler might have resulted in less cartridges required, for example in patients with wider pelvic cavities.

A potential confounder to the study could have been the size of the tumor and mesorectum, in relation to that of the pelvic cavity. While this was not stratified at randomization, the T-stage and tumor size of the two groups did not differ significantly.

Another unforeseen setback to the study was the longer than expected accrual period. Due to the COVID-19 pandemic, recruitment was interrupted due to social-distancing regulations. In addition, there were initial concerns regarding COVID-19 transmission from pneumoperitoneum, restrictions in operating theater resources, and a reduction in case referrals. Due to the extended study period, newer stapler models have been launched. Intuitive Surgical introduced the SureForm stapler as an upgrade to, and replacement for, the EndoWrist stapler. This new RS features SmartFire technology and an even greater range of articulation – 120-degrees. Similarly, the Medtronic Signia powered stapling system (Covidien, New Haven, CT) is an upgrade to existing conventional laparoscopic staplers, offering fully motorized stapler jaw movements and microprocessor-controlled firing. While the results from the current study may not be directly extrapolatable to other surgical staplers, the benefits of the RS in terms of surgeon autonomy and ergonomics would likely persist.

The EndoWrist stapler was more ergonomic to use than the conventional laparoscopic stapler. While this complemented the use of robotics in rectal surgery, it did not result in a significant reduction in the number of stapler cartridges required for rectal transection. Future studies should focus on the use of the new SureForm stapler, particularly in low rectal transections.

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No competing interests reported.

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A Comparison between the da Vinci Xi Endowrist Stapler and a conventional Laparoscopic Stapler in Rectal Transection: A Randomized Controlled Trial

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Abstract

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Materials And Methods

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Discussion

Conclusion

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