Comparison of Surgical Outcomes of da Vinci Surgical Systems X and Xi: A Single-center Study

doi:10.21203/rs.3.rs-4152339/v1

Background: The da Vinci surgical systems (X and Xi) are fourth-generation systems marketed by Intuitive Inc. The X system is less expensive compared with the Xi system. This study compared the surgical outcomes of patients who underwent hysterectomy using the X and Xi systems.

Methods: Data of 172 patients who underwent robot-assisted total hysterectomies by four surgeons between April 2019 and March 2023 were retrospectively analyzed in a single-center study. The patients were divided into two groups based on the system used for the surgery. Approval was granted by the Institutional Review Board of the Tottori University Hospital (22A134). All patients provided opt-out consent in accordance with institutional guidelines.

Results: The operative and console times in group X were shorter than those in group Xi after propensity score matching for age, body mass index, nulliparity, previous history of abdominal or pelvic surgery, pre-operative diagnosis, and surgical approach. No statistical differences were observed in a subgroup analysis of patients who underwent robot-assisted total laparoscopic hysterectomy without lymphadenectomy.

Conclusion: Perioperative outcomes for the X and Xi da Vinci surgical systems were equivalent. The cost-effective X system may allow the widespread use of robotic surgeries.

Hysterectomy

Robotic surgery

Treatment outcome

Cost effectiveness

Robot-assisted gynecological surgery was approved by the U.S. Food and Drug Administration in 2005 [1]. Robot-assisted hysterectomy is associated with reduced hospital stay, fewer complication and fewer blood transfusions than open surgery [2]. Furthermore, robot-assisted hysterectomy has an early learning curve [3]. Since its approval, various improvements have been made to the robots and new models have been released. The da Vinci Xi (Xi) is a fourth-generation surgical system that includes a greater endoscope, thinner arms, and an automated patient-side cart [4]. For radical prostatectomy, the docking and operation times of the Xi system are shorter than those of the da Vinci Si system [5].

Da Vinci X (X) is a fourth-generation system that was released 3 years after the Xi system and is more affordable [6]. The robotic arms of the X system are fixed to the patient-side cart. Therefore, access to target organs is sometimes impaired. However, the X and Xi systems use the same vision cart and surgeon console, and the instruments are interchangeable.

No previous studies have compared the Xi and X systems for hysterectomy. Robot-assisted hysterectomy using the Xi and X systems was introduced at our institution in 2018. This study compared the perioperative outcomes of patients who underwent robot-assisted hysterectomy with the da Vinci Xi and X systems.

The clinical records of 172 patients who underwent robot-assisted total hysterectomies by four surgeons at Tottori University Hospital between April 2019 and July 2023 were retrospectively reviewed. The patients who underwent sacrocolpopexy were excluded. The patients were divided into two groups based on the robotic system used for the surgery. The choice of the surgical system (X or Xi) was determined by the surgical department rather than the operating surgeon. Patient data, including age, body mass index (BMI), history of abdominal or pelvic surgery, parity, operative time, blood loss, uterine weight, frequency of perioperative adverse events (included Clavien-Dindo class II or higher), length of hospital stay, surgical approach (robot-assisted total laparoscopic hysterectomy [RATLH] or robot-assisted modified radical hysterectomy [RAmRH] and pelvic lymphadenectomy or not), and success rate of vaginal tissue removal were collected. The operative time was divided into pre-console time (defined as the time from the skin incision to the start of the console), console time, and post-console time (defined as the time from the end of the console to the end of the operation).

RATLH and RAmRH were conducted with the patient in an 18–20° head-down position. A closed or opened first-puncture approach was used, and the pneumoperitoneum pressure was set at 8–12 mmHg CO₂. Five port sites were used (Fig. 1). An automated setup function directed towards the pelvic floor was used when the Xi system was used. As the X system does not include a positioning function, the surgeons manually and subjectively adjusted the arms prior to docking (Fig. 2). During the operation, Maryland bipolar forceps, monopolar curved scissors, and a large needle driver were used. Furthermore, Cadiere forceps were used with the X system and Synchro Seal was used with Xi system. The second assistant used a Vagi pipe (Hakko Medical, Chikuma, Japan). The primary surgeons were certified by the Japan Society of Gynecologic and Obstetric Endoscopy and Minimally Invasive Therapy [7].

Propensity scores were used to control for potential covariate imbalances and create maximally non-biased groups. Propensity score matching involved the use of a logistic regression model based on six covariates: age, BMI, nulliparity, history of abdominal or pelvic surgery, pre-operative diagnosis, and surgical approach. The success of the matching was assessed for each variable using a standardized difference. A successful balance was inferred if the residual imbalance for all confounders was ≤10%.

Pearson's chi-square test and the Mann–Whitney U test were used to compare the categorical and continuous variables, respectively. Statistical significance was set at P < 0.05. All statistical analyses were conducted using SPSS Statistics for Windows (version 28, IBM Corp., Armonk, NY, USA). This study was performed in line with the principles of the Declaration of Helsinki. Approval was granted by the Institutional Review Board of the Tottori University Hospital (22A134). All patients provided opt-out consent in accordance with institutional guidelines.

A total of 172 patients underwent robot-assisted hysterectomy, including 95 (55.2%) and 77 (44.2%) for whom the X and Xi system was used, respectively (Table 1). After propensity score matching, 73 patients were included in each group. The demographic data and surgical approach used were not significantly different between the groups. RATLH was performed in approximately 70% of the patients in both groups. The mean number of harvested lymph nodes was 25.6 (± 9.9) with X and 28.9 (± 11.3) with Xi. The uterine weight and success rate of vaginal removal did not differ between the groups. No emergency conversion to open surgery was reported in either group.

The operative and console times were insignificantly shorter in group X than in group Xi (Table 2). There were no differences between the groups when the data of patients who underwent RATLH without lymphadenectomy were compared (Table 3). Despite the small sample size, no inferior aspects were identified in group X over group Xi in patients with BMI > 30 or uterine weight > 300 g (Online Resource 1 and 2).

To the best of our knowledge, this is the first study comparing the perioperative data of the X and Xi surgical systems for hysterectomy. Interestingly, the X system was not inferior to the Xi system and both systems were successfully used to perform hysterectomies. The operative and console times were shorter in group X than in group Xi, although the differences were insignificant. The surgeons reported similar frequencies of arm collisions in both groups.

A previous study reported that the pre-console time was significantly shorter, and the operative time tended to be shorter during total hysterectomy when the Xi system was used than with the Si system [8]. The X and Xi systems have been compared for other types of surgery. During robotic thyroidectomy surgery, the Xi system required a shorter operative time than the X system [9]. As the robotic arms of the X system are fixed to the patient-side cart, access to the patient’s head is impaired. However, Bergmann et al. [10] reported no serious adverse events associated with either system during rectal surgery. Therefore, the use of the two systems is expected to result in comparable outcomes since hysterectomy is a pelvic surgery. Advanced equipment, such as Synchro Seal, and the automated setup function of the Xi system may have accounted for the longer times in group X in this study.

Like the da Vinci Si system, the X system does not include an automated setup function. Furthermore, improvements to the operation fluency of the Xi system have resulted in a shorter operation time than that of the Si system [5]. Although a longer pre-operative time was expected in group X, there was no significant difference between the two groups in this study. Arm adjustments by the surgeons may have contributed to similar results between the two groups. Rama et al. [11] previously reported comparable docking times for the Si and Xi systems, suggesting the impact of the targeting process in the Xi system. Although the number of arm collisions was not reported in the current study, the surgeons did not report a difference in the frequency of collisions.

The intraoperative blood loss for robot-assisted hysterectomy has been reported as 77–119 mL and the adverse event rate as 2–13% [2, 12, 13], which are comparable to the results of the current study. The similar outcomes between both groups in this study may be attributed to the use of the same surgeon console and instruments.

This study has some limitations. First, the retrospective and single institution design have inherent limitations. Second, the long-term outcomes were not investigated. Although a detailed assessment was not performed, no notable adverse events were reported during the outpatient follow-up for 2 months in that study. Arms et al. [14] compared the long-term (4-month) satisfaction of women who underwent robot-assisted total hysterectomy. In addition, different surgeons may use different surgical techniques that may affect the study results.

To summarize, the perioperative outcomes of hysterectomy did not differ when the da Vinci X and Xi systems were used. Therefore, the less expensive X system resulted in adequate outcomes. These results may contribute to the widespread use of robotic surgery.

Funding

No funds, grants, or other support was received.

Competing interest

The authors have no relevant financial or non-financial interests to disclose.

Ethics approval

This study was performed in line with the principles of the Declaration of Helsinki. Approval was granted by the Institutional Review Board of the Tottori University Hospital (22A134). All patients provided opt-out consent in accordance with institutional guidelines.

Data availability

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available as they could compromise the privacy of research participants.

Authors’ contributions

All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by [Hiroaki Komatsu and Hiroki Nagata]. The first draft of the manuscript was written by [Hiroki Nagata] and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

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Table 1. Patient characteristics and surgical approach

	Before propensity score matching			After propensity score matching
	X system (n = 95)	Xi system (n = 77)	p-value	X system (n = 73)	Xi system (n = 73)	p-value	Sdiff
Age (years)	54.5 (± 13.3)	52.4 (± 12.4)	0.417	52.7 (± 12.7)	53.1 (±12.3)	0.559	0.035
BMI (kg/m²)	24.3 (± 5.4)	25.0 (± 7.3)	0.838	24.1 (± 5.1)	24.3 (± 6.4)	0.597	0.021
Nulliparity	23 (24.2%)	22 (28.6%)	0.601	18 (24.7%)	19 (26.0%)	1.000	0.031
Previous abdominal surgery	37 (38.9%)	36 (46.8%)	0.353	31 (42.5%)	33 (45.2%)	0.868	0.055
Benign tumor	50 (52.6%)	43 (55.8%)	0.759	41 (56.2%)	40 (54.8%)	1.000	0.028
RATLH	67 (70.5%)	54 (70.1%)	1.000	50 (68.5%)	51 (69.9%)	1.000	0.030
RAmRH	28 (29.5%)	23 (29.9%)	-	23 (31.5%)	22 (30.1%)	-	-
Lymphadenectomy	24 (25.3%)	19 (24.7%)	1.000	20 (27.4%)	18 (24.7)	0.851	0.062

Abbreviations

Sdiff: Standardized difference, RATLH: Robot assisted total hysterectomy, RAmRH: Robot assisted modified radical hysterectomy, BMI: body mass index

Data are presented as means (±standard deviation) or as n (%).

Table 2. Surgical results of all patients

	X system (n = 73)	Xi system (n = 73)	p-value
Operative time (min)	147.2 (±43.0)	162.3 (±53.0)	0.129
Pre-console time (min)	19.7 (±7.0)	20.0 (±7.2)	0.712
Console time (min)	111.9 (±40.3)	126.6 (±46.3)	0.074
Post-console time (min)	15.6 (±9.3)	15.4 (±10.1)	0.687
Blood loss (mL)	40.2 (±79.6)	46.8 (±77.6)	0.359
Length of hospital stay (day)	4.7 (±1.0)	6.3 (±10.1)	0.113
Complications	7 (9.6%)	7 (9.6%)	1.000
Uterine weight (g)	181.5 (±146.9)	168.7 (±120.2)	0.704
Uterine removal via the vagina	71 (97.3%)	69 (95.9%)	0.681

Data are presented as means (±standard deviation) or as n (%).

Table 3. Surgical results of patients who underwent RATLH without lymphadenectomy

	X system (n = 50)	Xi system (n = 48)	p-value
Operative time (min)	126.6 (±29.5)	138.2 (±38.5)	0.201
Pre-console time (min)	20.2 (±7.5)	19.3 (±4.4)	0.901
Console time (min)	92.9 (±27.0)	105.5 (±34.7)	0.089
Post-console time (min)	13.4 (±6.1)	13.5 (±5.6)	0.780
Blood loss (mL)	36.4 (±71.7)	42.9 (±74.9)	0.341
Length of hospital stay (days)	4.3 (±0.647)	6.7 (±12.4)	0.089
Complications	5 (10.0%)	3 (6.3%)	0.715
Uterine weight	171.8 (±114.3)	181.7 (±133.4)	0.926
Uterine removal via the vagina	50 (100%)	45 (93.8%)	0.114

RATLH: Robot assisted total laparoscopic hysterectomy

Data are presented as means (±Standard Deviation) or as n (%).

No competing interests reported.

Supplementaryfile.docx
Supplementary information Supplementary Table 1. Surgical results of patients who underwent RATLH without lymphadenectomy (BMI >30 kg/m² only) Supplementary Table 2. Surgical results of patients who underwent RATLH without lymphadenectomy (uterine >300 g only)

Comparison of Surgical Outcomes of da Vinci Surgical Systems X and Xi: A Single-center Study

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