Abstract
Background and Objectives:
To demonstrate the feasibility and potential of robotic single-site cholecystectomy, the study aimed to compare it with conventional laparoscopic cholecystectomy.
Methods:
In total, 791 consecutive patients underwent conventional laparoscopic cholecystectomy or robotic single-site cholecystectomy at our center between 2019 and 2022. After 1:1 propensity score matching, 117 patients for each group were selected.
Results:
After propensity score matching, the only statistically significant difference between conventional laparoscopic cholecystectomy and robotic single-site cholecystectomy was operative time, which was 29.15 ±11.45 min in the conventional laparoscopic cholecystectomy group versus 38.57 ± 12.59 min in the robotic single-site cholecystectomy group (P < 0.001). Because the difference in surgical time between the two groups was minimal, it has little clinical relevance. Using cumulative sum analysis, the maturation phase of the total operation and docking times occurred after the 53rd case. To reduce bias, a comparison of results with conventional laparoscopic cholecystectomy and cases of robotic single-site cholecystectomy was performed in the maturation phase, which revealed only total operative time as statistically significant (P < 0.001).
Conclusion:
Robotic single-site cholecystectomy is a technically feasible and safe method for treating benign gallbladder diseases, with a relatively short learning curve and reasonable operative time.
Keywords: Benign gallbladder disease, Cumulative sum analysis, Learning curve, Propensity score matching, Robotic single site cholecystectomy
INTRODUCTION
Single-incision surgery is the result of ongoing trends in minimally invasive laparoscopy and is preferred by patients over multiport laparoscopic surgery. Moreover, surgeons have been trying to reduce pain and hospital stays and minimize the size of surgical incisions through technical improvements.1
The use of laparoscopic cholecystectomy, a well-known method for the treatment of benign gallbladder diseases, is also changing in line with this trend. With efforts to reduce the number of ports in laparoscopic cholecystectomy, single-incision laparoscopic cholecystectomy (SILC) and robotic single-site cholecystectomy (RSSC) have evolved. The former surgical method has already proven its inherent limitations and drawbacks.2–7 In a meta-analysis, SILC seemed to increase adverse events compared to conventional laparoscopic cholecystectomy (CLC). RSSC, on the other hand, has overcome the shortcomings of SILC, such as narrowing of the working space, improper triangulation, collision between laparoscopic instruments, and challenges in delicate movement by maximizing the advantage of single incision surgery.2,5,7–9
In the present study, RSSC was conducted for three years, and it was during this period that the early experience of RSSC10 was compared to the results of CLC. Furthermore, to eliminate the bias of the RSSC as an initial experience, the learning curve was determined. Thus, the present study aimed to demonstrate the feasibility and potential of RSSC.
MATERIALS AND METHODS
Study Population
Between January 1, 2019 and December 31, 2022, 791 consecutive patients underwent RSSC or CLC performed by a single surgeon at Dong-A University Hospital. RSSC was performed in 175 patients, and CLC was performed in 616 patients. Of these, 175 patients who visited the emergency department and 28 who underwent combined surgery were excluded from the CLC group to reduce bias (Figure 1). The exclusion criteria for RSSC selection were the following: 1) diagnosed with severe acute cholecystitis, 2) patients who visited the emergency department, 3) with suspected malignancy, and 4) refusal to undergo RSSC due to cost.
Figure 1.
Study design with a flow diagram.
After obtaining Institutional Review Board approval, data were collected retrospectively, and propensity score matching (PSM) was conducted to address the selection bias. After a 1:1 PSM, 117 patients were selected from each group.
Surgical Procedures
Robotic Single-Site Cholecystectomy
The patients were placed in the supine and reverse Trendelenburg positions, with both arms secured at the sides of the body. A 2 – 2.5-cm transumbilical incision was made. A glove port (NELIS; Bucheon, Korea) was inserted through the incision. When pneumoperitoneum was established, the DaVinci Xi® system (Intuitive Surgical, Sunnyvale, CA) was positioned at the right upper section. We inserted an 8 mm camera cannula into the blue channel and targeted the gallbladder. Subsequently, a 5 × 250-mm curved cannula was inserted on the right side into the white channel for a permanent cautery hook. The same cannula was inserted under the hook on the left side of the crocodile grasper. Subsequently, the first assistant retracted the gallbladder cranially using a laparoscopic grasper through another white channel. The docking time was from the skin incision to this point. Once all the ports were in place, the cystic duct and artery were ligated using robotic Hem-o-lok® clips (Weck® Closure System; Research Triangle Park, NC, USA). Finally, the gallbladder was dissected from the fossa and retrieved using a glove port. The fascia was then closed using interrupted sutures. Detailed methods were the same as in a previous paper.10
Conventional Laparoscopic Cholecystectomy
The patients were prepared for RSSC. All CLCs were performed by installing a 12-mm periumbilical port, 5-mm right flank port, and 5-mm subxiphoid area. The surgical procedure was conducted by clarifying Calot’s triangle dissection, ligating the cystic duct and cystic artery using 5 mm Hem-o-lok® clips (Weck® Closure System, Research Triangle Park, NC, USA), and removing the gallbladder from the liver bed. The gallbladder was removed using an endobag through the periumbilical port. The fascia and skin were closed routinely.
Statistical Analyses
The results are expressed as percentages for category variables and mean ± standard deviation for continuous variables. The t test or Mann-Whitney U-test was performed for continuous variables, and the χ2 or Fisher’s exact tests were used for the analysis of categorical variables. PSM was used to account for confounding factors according to indication. The propensity score was estimated using a logistic regression model with the following covariates: gender, age, body mass index (BMI), American Society of Anesthesiologists (ASA) physical status classification, preoperative diagnosis, presence or absence of preoperative symptom, preoperative abdominal operation history, difficulty of operation (adhesion around gallbladder wall, thickening of gallbladder wall, fibrosis of Calot’s triangle). SAS version 9.4 (SAS Institute Inc., Cary, North Carolina, United States) was used for statistical analysis. Statistical significance was set at P < 0.05. A cumulative sum analysis (CUSUM) was performed. The cases were ordered chronologically, and denotes the total operative time of the docking time for each patient, and μ is the mean of each time. Therefore, CUSUM at the total operative and docking times were calculated as follows.11
Ethical Approval
This study was reviewed and approved by Institutional Review Board. The requirement for informed consent was waived because of the retrospective nature of this study. The study was conducted in accordance with the principles of the Declaration of Helsinki.
RESULTS
Demographic and Perioperative Factors
Between January 1, 2019 and December 31, 2022, RSSC or CLC was performed on 791 consecutive patients by a single surgeon at Dong-A University Hospital. RSSC was performed on 175 patients, and CLC was performed on 616 patients. Of these, 175 patients who visited the emergency department and 28 patients who underwent combined surgery were excluded from the CLC group. Between the two groups, all factors, including sex, age, BMI, preoperative diagnosis, preoperative symptoms, preoperative abdominal operation history, and difficulty of operation, were statistically significant (P < 0.001). Thus, 1:1 PSM was used to correct for selection bias, which revealed no significant differences in 117 patients in each group in any of the preoperative factors (Table 1).
Table 1.
Patient Characteristics Before and After Propensity Score Matching
| Variables | Unmatched Data | Matched Data | ||||||
|---|---|---|---|---|---|---|---|---|
| Method | Method | |||||||
| 1 |
2 |
Total |
P-value | 1 |
2 |
Total |
P-value | |
| 413 | 175 | 588 | 117 | 117 | 234 | |||
| Sex | 0.010 | 0.504 | ||||||
| Male, N (%) | 201 (48.7) | 65 (37.1) | 266 (45.2) | 44 (37.6) | 49 (41.9) | 93 (39.7) | ||
| Female, N (%) | 212 (51.3) | 110 (62.9) | 322 (54.8) | 73 (62.4) | 68 (58.1) | 141 (60.3) | ||
| Age (year) | 55.6 ± 13.3 | 45 ± 10.7 | 52.5 ± 13.5 | < 0.001 | 47.9 ± 12 | 48.2 ± 9.9 | 48.1 ± 11 | 0.831 |
| BMI (kg/m2) | 25. ± 4 | 23.8 ± 3.4 | 24.7 ± 3.9 | < 0.001 | 24.4 ± 3.9 | 24.5 ± 3.3 | 24.5 ± 3.6 | 0.941 |
| ASA (score) | 1.88 ± . 67 | 0.20 ± . 40 | 1.38 ± . 98 | < 0.001 | 1.62 ± . 64 | 1.64 ± . 53 | 1.63 ± . 59 | 0.740 |
| Preoperative diagnosis | < 0.001 | 0.725 | ||||||
| Acute cholecystitis, N (%) | 39 (9.4) | 10 (5.7) | 49 (8.3) | 9 (7.7) | 8 (6.8) | 17 (7.3) | ||
| GB stone, N (%) | 273 (66.1) | 103 (58.9) | 376 (63.9) | 78 (66.7) | 73 (62.4) | 151 (64.5) | ||
| ADM, N (%) | 18 (4.4) | 25 (14.3) | 43 (7.3) | 10 (8.5) | 9 (7.7) | 19 (8.1) | ||
| GB polyp, N (%) | 83 (20.1) | 37 (21.1) | 118 (20.4) | 20 (17.1) | 27 (23.1) | 47 (20.1) | ||
| Symptom | 0.210 | 0.081 | ||||||
| No, N (%) | 256 (62.0) | 118 (67.4) | 374 (63.6) | 65 (55.6) | 78 (66.7) | 143 (61.1) | ||
| Yes, N (%) | 157 (38.0) | 57 (32.6) | 214 (36.4) | 52 (44.4) | 39 (33.3) | 91 (38.9) | ||
| OP history | < 0.001 | 0.497 | ||||||
| No, N (%) | 297 (71.9) | 80 (45.7) | 377 (64.1) | 77 (65.8) | 72 (61.5) | 149 (63.7) | ||
| Yes, N (%) | 116 (28.1) | 95 (54.3) | 211 (35.9) | 40 (34.2) | 45 (38.5) | 85 (36.3) | ||
| Adhesion | < 0.001 | 0.909 | ||||||
| Absent, N (%) | 170 (41.2) | 109 (62.3) | 279 (47.4) | 67 (57.3) | 64 (54.7) | 131 (56.0) | ||
| Moderate, N (%) | 195 (47.2) | 59 (33.7) | 254 (43.2) | 44 (37.6) | 46 (39.3) | 90 (38.5) | ||
| Severe, N (%) | 48 (11.6) | 7 (4.0) | 55 (9.4) | 6 (5.1) | 7 (6.0) | 13 (5.6) | ||
| Thickening | < 0.001 | 0.958 | ||||||
| Absent, N (%) | 162 (39.2) | 107 (61.1) | 269 (45.7) | 63 (53.8) | 62 (53.0) | 125 (53.4) | ||
| Moderate, N (%) | 202 (48.9) | 61 (34.9) | 263 (44.7) | 48 (41.0) | 48 (41.0) | 96 (41.0) | ||
| Severe, N (%) | 49 (11.9) | 7 (4.0) | 56 (9.5) | 6 (5.1) | 7 (6.0) | 13 (5.6) | ||
| Fibrosis | < 0.001 | 0.861 | ||||||
| Absent, N (%) | 163 (39.5) | 105 (60.0) | 268 (45.6) | 65 (55.6) | 61 (52.1) | 126 (53.8) | ||
| Moderate, N (%) | 201 (48.7) | 63 (36.0) | 264 (44.9) | 46 (39.3) | 49 (41.9) | 95 (40.6) | ||
| Severe, N (%) | 49 (11.9) | 7 (4.0) | 56 (9.5) | 6 (5.1) | 7 (6.0) | 13 (5.6) | ||
BMI, body mass index; ASA, American Society of Anesthesiologists; GB, gallbladder; ADM, adenomyomatosis; OP, operation.
Operative Outcomes
In our paper, the operation time was defined as either 1) total operation time: spanning from the initial skin incision to final skin closure, or 2) docking time: spanning from the skin incision to the installation of the second robotic arm into the cannula.10 After PSM, the only statistically significant difference between CLC and RSSC was operative times: 29.15 ± 11.45 minutes in the CLC group versus 38.57 ± 12.59 minutes in the RSSC group (P < 0.001). The total operative time in CLC and total operative time except docking time in RSSC were not statistically different. Other postoperative outcomes, including hospital stay and postoperative day 1 pain scores, were not significantly different. Although the open conversion rate and complications could not be statistically proven after PSM, there seemed to be no significant difference between the two groups, even before PSM (Table 2). No additional ports were used in either group.
Table 2.
Operative Outcomes Before and After Propensity Score Matching
| Variables | Unmatched Data | Matched Data | ||||
|---|---|---|---|---|---|---|
| Method | P-value | Method | P-value | |||
| 1 |
2 |
1 |
2 |
|||
| 413 | 175 | 117 | 117 | |||
| Open conversion | N/A | |||||
| No, N (%) | 411 (99.5) | 175 (100.0) | 0.356 | 117 (100.0) | 117 (100.0) | |
| Yes, N (%) | 2 (0.5) | 0 (0.0) | 0 (0.0) | 0 (0.0) | ||
| Optime (min) | 30.8 ± 12.9 | 37.7 ± 12 | < 0.001 | 29.2 ± 11.5 | 38.6 ± 12.6 | < 0.001 |
| Optime except docking time (min) | N/A | 31.3 ± 10.9 | 0.660 | N/A | 31.9 ± 11.3 | 0.059 |
| Hospital stay (days) | 2.5 ± 1.4 | 2.4 ± . 91 | 0.174 | 2.4 ± 1.1 | 2.4 ± . 77 | 0.724 |
| Pain NRS (POD #1) | 3.1 ± . 86 | 2.9 ± . 79 | 0.153 | 3.1 ± . 87 | 2.9 ± . 78 | 0.239 |
| Complication | N/A | |||||
| No, N (%) | 411 (99.5) | 175 (100.0) | 0.892 | 117 (100.0) | 117 (100.0) | |
| Yes, N (%) | 2 (0.5) | 1 (0.6) | 0 (0.0) | 0 (0.0) | ||
OP, operation; NRS, numeric rating score; POD, postoperative day; Optime, operative time.
Cumulative Sum Analysis in Total Operative Time and Docking Time
The total operative time was plotted in chronological order. The CUSUMOT learning curve consists of three phases: 1) the initial phase (1 – 18 cases), 2) intermediate phase (19 – 53 cases), and 3) maturation phase (54 cases) (Figure 2A). Subsequently, the CUSUMDT of the maturation phase occurred after the 53rd case (Figure 2B).
Figure 2.
Analysis of robotic single-site cholecystectomy. A) Learning curve for total operative time: Changes in operative times in chronological order (black). Cumulative sum analysis (CUSUM) (blue). B) Learning curve for docking time: changes in operative times in chronological order (black). CUSUM (blue).
Operative Outcomes After Learning Curve of Robotic Single-Site Cholecystectomy
Supplement 1 shows the demographics and perioperative factors of the patients after the RSSC learning curve, before and after PSM. Comparing the results with the CLC and the cases of the maturation phase of RSSC using PSM, statistical significance was found only on total operative time (P < 0.001) (Table 3). Other postoperative outcomes, such as hospital stay and postoperative day 1 pain score, were not statistically different.
Table 3.
Operative Outcomes After Learning Curve of Robotic Single-site Cholecystectomy
| Variables | Unmatched Data | Matched Data | ||||
|---|---|---|---|---|---|---|
| Method | P-value | Method | P-value | |||
| 1 |
2 |
1 |
2 |
|||
| 413 | 122 | 99 | 99 | |||
| Open conversion | > 0.999 | N/A | ||||
| No, N (%) | 411 (99.5) | 122 (100) | 99 (100) | 99 (100) | ||
| Yes, N (%) | 2 (0.5) | 0 (0) | 0 (0) | 0 (0) | ||
| Optime (min) | 30.8 ± 12.9 | 35.4 ± 11.0 | < 0.001 | 27.8 ± 10 | 35.8 ± 11.4 | < 0.001 |
| Hospital stay (days) | 2.5 ± 1.4 | 2.3 ± 0.9 | 0.137 | 2.2 ± 0.7 | 2.3 ± 0.6 | 0.882 |
| Pain NRS (POD #1) | 3.1 ± . 86 | 2.9 ± 0.7 | 0.005 | 3.0 ± 0.8 | 2.8 ± 0.6 | 0.034 |
| Complication | 0.541 | N/A | ||||
| No, N (%) | 411 (99.5) | 121 (99.2) | 99 (100) | 99 (100) | ||
| Yes, N (%) | 2 (0.5) | 1 (0.8) | 0 (0) | 0 (0) | ||
OP, operation; NRS, numeric rating score; POD, postoperative day; Optime, operative time.
DISCUSSION
As RSSC has emerged as a major method of cholecystectomy, previous studies have confirmed its efficacy compared with other surgical methods.4,6,12–17 In most studies, compared with CLC and SILC, RSSC showed similar results in terms of surgical outcomes while maximizing the advantages of single-incision surgery, demonstrating its safety and feasibility.
To our knowledge, this is the first study to compare the surgical outcomes of RSSC by controlling for surgical difficulty. Factors that determine the difficulty of surgery include adhesion around the gallbladder wall, thickening of the gallbladder wall, and fibrosis of Calot’s triangle, which are classified as absent, moderate, or severe. Determining the difficulty of surgery may be a subjective judgment; however, because the difficulty of all surgeries was judged by one surgeon, it could be an objective criterion. This study used PSM to control not only the difficulty of surgery but also other confounding factors that can affect the results, enabling an accurate comparison of surgical outcomes between the two groups.
When comparing the outcomes of surgery between the two groups, it may be questionable to compare the results of the first experience with RSSC, and many experienced CLC at the same time. Therefore, RSSC cases were compared with CLC after the learning curve. Other studies have revealed that the maturation phase of RSSC occurs after 19–50 cases18 and that the operation time will decrease after 55–85 cases.19 Similar to the findings of the present study, the maturation phases of the total operative time and docking time are after 18–53 cases and 37–53 cases, respectively (Figure 2A and B). The initial learning curve of docking time is longer than the total operation time, which is necessary to adapt to a new procedure that was not included in CLC. To reduce bias, surgical outcomes were compared between patients after the maturation phase of the RSSC and CLC groups, which revealed a significant difference in operative time in the two groups (Table 3). As shown in Tables 2 and 4, the average total operative time between the two groups decreased from 9.42 min to 7.99 min, but this was not statistically significant. In addition, the average operation time of RSSC was 37.70 ± 11.9 min in the present study, which was significantly shorter compared to the results of previous studies,1,12,14–16,20 with an average operation time of 61.02 ± 27.5 min to 101.57 ± 27.1 min. Hence, it may be difficult to reduce the total operative time even after the learning curve, and it could not be clinically significant.
Along with the efforts to reduce the number of ports, SILC and RSSC have emerged. SILC was found to have a higher incidence rate of bile duct injury during surgery or bile leakage after surgery than RSSC because of better ergonomics and advantages in acquiring a critical view of safety.4,6,18,20 However, in both groups, wound infection and port-site hernias should be considered carefully. In several recent papers,12,14,15 including systemic reviews,1 wound infection, and port site hernia rates are 4.7–6.6% and 6.5%–7.1%, respectively. However, there was one port site hernia in 175 patients conducted in our center (Table 2). In order to prevent these complications, extreme attention must be taken when closing the umbilical wound, as it is a very serious complication.
This study had several limitations. It had a retrospective design and involved only one surgeon in a small center. Multicenter trials are needed in the near future to validate the advantages of RSSC. Additionally, it is necessary to study the learning curve and surgical outcomes of RSSC for surgeons who are beginners in CLC.
In conclusion, RSSC is a technically feasible and safe method with a relatively short learning curve for benign gallbladder diseases because RSSC is comparable to CLC in terms of not only operative time but also postoperative results clinically, even though total operative time statically significantly longer than CRC. Therefore, RSSC can be an alternative surgical method for the management of benign gallbladder disease.
Footnotes
Disclosure: none.
Conflict of interests: none.
Funding sources: This study was supported by the Dong-A University Research Fund. The Dong-A university research fund had no part in the design, execution, analysis, or writing of the study, or the decision to submit for publication. No other entity had a role in funding, writing, designing, analyzing, or sponsoring the study.
Informed consent: Dr. Kwan Woo Kim declares that written informed consent was obtained from the patient/s for publication of this study/report and any accompanying images.
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