Hidetoshi Katsuno; Koji Morohara; Tomoyoshi Endo; Kenji Kikuchi; Kenichi Nakamura; Kazuhiro Matsuo; Takahiko Higashiguchi; Tetsuya Koide; Hiromi Kanai; Satoshi Arakawa; Tsunekazu Hanai; Zenichi Morise

doi:10.3393/ac.2025.00136.0019

Articles

Page Path: HOME > Ann Coloproctol > Volume 41(4); 2025 > Article

Original Article Minimally invasive surgery Propensity score–matched comparison of robot-assisted rectal cancer surgery using hinotori and da Vinci: Hidetoshi Katsuno¹, Koji Morohara¹, Tomoyoshi Endo¹, Kenji Kikuchi¹, Kenichi Nakamura¹, Kazuhiro Matsuo¹, Takahiko Higashiguchi¹, Tetsuya Koide¹, Hiromi Kanai¹, Satoshi Arakawa², Tsunekazu Hanai², Zenichi Morise¹; Annals of Coloproctology 2025;41(4):310-318.
DOI: https://doi.org/10.3393/ac.2025.00136.0019
Published online: August 25, 2025

¹Department of Surgery, Okazaki Medical Center, Fujita Health University, Okazaki, Japan

²Department of Gastrointestinal Surgery, Fujita Health University Bantane Hospital, Nagoya, Japan

Correspondence to: Hidetoshi Katsuno, MD, PhD Department of Surgery, Okazaki Medical Center, Fujita Health University, Gotanda 1, Harisaki, Okazaki, 444-0827, Japan Email: katsuno@fujita-hu.ac.jp

• Received: February 8, 2025 • Revised: April 29, 2025 • Accepted: April 29, 2025

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

prev next

2,943 Views
54 Download
1 Web of Science
1 Crossref
1 Scopus

Full Article

Download PDF

Abstract
Graphical abstract
INTRODUCTION
METHODS
RESULTS
DISCUSSION
ARTICLE INFORMATION
REFERENCES

Abstract

Purpose
The hinotori Surgical Robot System (hereafter “hinotori”) is a novel platform for robot-assisted surgery, while the da Vinci Surgical System (“da Vinci”) remains the field standard. This study compared short-term surgical outcomes of rectal cancer surgery between these systems using propensity score–matched analysis.
Methods
A retrospective analysis was conducted of 209 consecutive patients who underwent robot-assisted surgery with the da Vinci and 58 patients with the hinotori system. After 2:1 propensity score matching, 108 da Vinci and 54 hinotori cases were included. Surgical outcomes, including operative time, blood loss, postoperative complications, length of hospital stay, and pathological findings, were compared.
Results
After matching, the baseline demographics were well balanced between groups. The hinotori system was associated with significantly longer operative time (266 minutes vs. 227 minutes, P=0.014) and console time (156 minutes vs. 110 minutes, P=0.001). However, estimated blood loss and postoperative complication rate did not differ significantly. Pathological findings, including the number of lymph nodes retrieved and the incidence of positive surgical margins, were comparable between systems.
Conclusion
In rectal surgery, the hinotori system demonstrates comparable short-term safety outcomes to da Vinci. Despite longer operative times and limited integrated instrumentation, hinotori‐assisted procedures may be feasible in selected patients. Further research should address long-term oncological outcomes and strategies to improve procedural efficiency.
Keywords: Rectal neoplasms; Robotic surgical procedures; Propensity score; Postoperative complications

Graphical abstract

INTRODUCTION

Robot-assisted surgery has revolutionized the treatment of rectal cancer, offering increased precision, improved visualization, and reduced surgeon fatigue compared with conventional laparoscopic or open approaches. The introduction of the da Vinci Surgical System (Intuitive Surgical; hereafter “da Vinci”) marked a major milestone in this evolution and has become the worldwide standard platform for robot-assisted procedures. Randomized controlled trials [1–3], meta-analyses [4], and studies employing propensity score matching (PSM) [5, 6] have consistently demonstrated the efficacy and safety of robot-assisted rectal cancer surgery, reporting lower conversion rates, better preservation of autonomic nerves [4, 6], and superior oncological outcomes versus laparoscopic techniques [3]. Despite these advances, concerns regarding cost-effectiveness and widespread adoption persist [7], leaving space for alternative robotic platforms to emerge in the area of surgical innovation.

The field of robot-assisted surgery has entered a new era of intensified competition and innovation. Platforms such as the hinotori Surgical Robot System (“hinotori”)—developed by Medicaroid Corporation as an alternative to the da Vinci—are now being integrated into clinical practice [8, 9]. This diversification is expected to initiate a “technological race in robot-assisted surgical platforms,” compelling healthcare providers to address challenges including the rigorous validation of safety and efficacy, standardization of surgical training, and mitigation of escalating healthcare costs. As additional platforms become available, comparative studies are essential to guide evidence-based adoption and to prioritize patient safety and outcomes.

The hinotori system, developed in Japan and approved for clinical use in 2020, represents the country’s first domestically manufactured surgical robotic platform. It offers advanced features including 8-axis robotic arms for superior precision, a docking-free calibration system that streamlines setup, and an ergonomic 3-dimensional (3D) viewer to minimize surgeon fatigue. Early investigations have demonstrated its safety, feasibility, and outcomes comparable to those of the da Vinci system [8], supporting the need for further comparative evaluations.

To date, 2 PSM studies have compared surgical outcomes between hinotori and da Vinci in urologic oncology [10, 11]; however, no such analysis has been performed for colorectal cancer. Because our institution houses both robotic platforms, we conducted a direct comparison of their short-term outcomes using PSM. This study evaluates key parameters such as operative time, blood loss, and perioperative complications to provide critical insight into the clinical feasibility and system equivalence of hinotori in robot-assisted rectal cancer surgery.

METHODS

Ethics statement

This study was approved by the Institutional Review Board of Fujita Health University (No. HM24-029). Informed consent was waived due to the retrospective nature of the study. All patient data were anonymized. The study protocol adhered to the Declaration of Helsinki.

Patients

This study enrolled patients who underwent robot-assisted surgery for rectal neoplasm with either the da Vinci system (group D) or the hinotori system (group H) between July 2020 and December 2024. Fujita Health University (Toyoake, Japan) has been a leader in robot-assisted surgery in Japan, performing the nation’s first colorectal cancer procedure with the da Vinci S in 2009 [12]. Okazaki Medical Center (Okazaki, Japan)—opened in April 2020—is equipped with both da Vinci Xi and the hinotori platforms. All procedures in group D were performed using the da Vinci Xi, which became available at our center in July 2020. The hinotori system was introduced in January 2023 after obtaining insurance coverage for gastrointestinal surgical applications in October 2022.

Patient characteristics, including age, sex, body mass index, and clinical stage of the disease, were documented. Preoperative staging employed colonoscopy, barium enema, computed tomography, and magnetic resonance imaging, with TNM classification based on the Japanese Classification of Colorectal, Appendiceal, and Anal Carcinoma, 9th edition [13]. Under this system, the rectum is defined as extending from the sacral promontory to the upper edge of the anal canal, making enema studies essential for accurately delineating tumor extent. Baseline characteristics were compared between groups to confirm balanced cohorts. Postoperative outcomes were tracked for at least 30 days. Two lead surgeons (H Katsuno and K Morohara)—each accredited by the Japanese Society of Endoscopic Surgery’s Endoscopic Surgical Skill Qualification System and having performed over 100 da Vinci-assisted procedures—served as primary console surgeons.

hinotori Surgical Robot System

The hinotori system was utilized in this study, showcasing its distinctive features and surgical potential [14]. Engineered for compactness, safety, and operational efficiency, the system comprises 3 main components: a surgeon’s cockpit, an operation unit with 4 robotic arms, and a high-definition monitor cart (Fig. 1). The arms, each with 8 axes, increase maneuverability and precision while minimizing the risk of collisions. A standardized port configuration was adopted, consisting of four 8-mm robotic trocars arranged diagonally from the right lower quadrant to the left upper quadrant, along with a 12-mm assistant port. Fig. 2 illustrates both the port placement and the instruments assigned to each robotic arm.

One of hinotori’s key innovations is its docking-free calibration mechanism—termed the pivot position—which enables manual adjustment of trocar placement to create a flexible workspace and minimize tissue trauma caused by excessive tension (Fig. 3). The surgeon cockpit incorporates an adjustable 3D viewer with an ergonomic design to reduce fatigue, alongside a high-definition 16:9 monitor that expands the field of view and improves procedural accuracy.

Although the hinotori system represents several innovations, it also has certain limitations. Unlike the da Vinci system, it does not include a dedicated linear stapler for rectal transection, requiring the assistant to perform this step manually and potentially increasing procedural complexity. Furthermore, the system lacks integrated vessel-sealing and ultrasonic dissection capabilities.

Statistical analysis

PSM was employed to minimize selection bias and balance baseline characteristics between groups D and H. The conditional probability of receiving either robotic platform was estimated using a logistic regression model that included 11 covariates: age, sex, body mass index, American Society of Anesthesiologists (ASA) physical status, tumor size, tumor distance from the anal verge, presence of multiple primary colorectal cancers, T category, N category, clinical oncological stage, and receipt of neoadjuvant chemotherapy. Nearest neighbor matching without replacement was performed using a caliper width of 0.2 standard deviations of the logit of the propensity score. Patients outside the caliper range or otherwise unmatched were excluded. Post-PSM balance was assessed based on the standardized mean difference between groups, with values of less than 0.1 considered to indicate acceptable balance.

The results are presented as medians with interquartile ranges for continuous variables and as numbers with percentages for categorical variables. Because the data were not normally distributed, nonparametric tests were applied: continuous variables were compared using the Mann-Whitney U-test and categorical variables using the chi-square test or Fisher exact test. Two-tailed P-values of less than 0.05 were considered to indicate statistical significance. Statistical analyses were performed with EZR ver. 1.68 (Saitama Medical Center, Jichi Medical University), and R ver.4.3.1 (R Foundation for Statistical Computing).

RESULTS

Patient characteristics and PSM

A total of 266 patients were analyzed, including 209 in group D and 57 in group H. Using 2:1 PSM, matched cohorts of 108 da Vinci recipients and 54 hinotori recipients were established (Table 1). After matching, baseline demographic factors and preoperative clinical parameters displayed no significant differences between groups, confirming that the matching process successfully balanced the cohorts and thus reduced potential biases due to patient background disparities. Consequently, the matched groups provided a robust foundation for comparative analysis of intraoperative and postoperative outcomes.

Surgical outcomes

Surgical outcomes differed between the groups in several respects (Table 2). The median operative time was significantly longer in group H than in group D (266 minutes vs. 227 minutes, P=0.014), as was the median console time (156 minutes vs. 110 minutes, P=0.001). Similarly, the median interval from skin incision to console activation was prolonged in group H (20 minutes vs. 16 minutes, P=0.013). Estimated blood loss was minimal and was comparable between groups (15 mL vs. 14.5 mL, P=0.563). Notably, no conversions to laparotomy occurred in either group.

Postoperative outcomes were generally comparable between groups. The overall complication rate was 9.3% in group H versus 13.9% in group D (P=0.458), and the distribution of complications by Clavien-Dindo grade did not differ significantly. Median hospital stay was significantly shorter in group H compared with group D (11 days vs. 14 days, P=0.002). Readmissions within 30 days were infrequent, occurring in 1 patient (0.9%) in group D and none in group H (P=0.892).

Pathological findings

Pathological outcomes were comparable between the 2 groups, with no significant differences observed. Both cohorts had a median of 21 harvested lymph nodes. The distal resection margin was slightly larger in group H than in group D, although this difference did not reach statistical significance (P=0.293). Radial margin positivity was rare, observed in 1 patient (0.9%) in group D and none in group H (P>0.999). Pathological staging distributions were also similar between groups (P=0.279) (Table 3).

DISCUSSION

The successful application of PSM ensured balanced baseline characteristics between groups D and H, thereby minimizing confounding biases related to demographic or clinical differences. A nearest neighbor matching strategy with an optimized caliper width was adopted, aligning with prior methodological research [15], to maximize comparability of the matched cohorts.

This comprehensive methodological framework supports the reliability of our comparative analyses and enables a more accurate assessment of hinotori’s performance relative to the da Vinci system. The lack of significant differences in preoperative parameters confirms that matching produced comparable cohorts, reinforcing the validity of the subsequent comparisons of intraoperative and postoperative outcomes.

The significantly longer operative and console times observed with group H can be attributed to several factors. Learning curves inherent to newly adopted robotic systems require surgeons to master unfamiliar interfaces and ergonomics. As such, the hinotori platform—introduced only recently compared to the well-established da Vinci—likely imposed an initial proficiency gap. In its early clinical rollout, hinotori also presented hardware constraints, including the absence of a hand clutch and less intuitive foot pedal configurations, that may have impacted surgical ergonomics and workflow. These factors likely contributed to longer operative times during initial clinical use. However, recent improvements, including the addition of a hand clutch, redesigned foot pedals for improved usability, and multiple software updates, have addressed these limitations [8]. Despite the temporal differences observed, the comparable estimated blood loss and the absence of conversions to laparotomy in both groups support the safety and technical feasibility of the hinotori system. Future research should investigate whether increased surgeon experience with hinotori, along with ongoing refinements of its hardware and software, can further reduce operative times to levels comparable with those of the da Vinci.

Postoperative outcomes revealed comparable safety profiles in both groups, as evidenced by similar complication rates and Clavien-Dindo grade distributions. Notably, the median postoperative hospital stay was significantly shorter in group H than in group D. Although our data lacked postoperative pain scores, this shorter length of stay for the hinotori cohort may partly reflect decreased physical stress attributable to its pivot-based docking mechanism. Supporting this, a recent study at our main hospital [16] found a significantly lower incidence of subcutaneous emphysema after hinotori-assisted rectal cancer surgery versus da Vinci Xi-assisted procedures. Because subcutaneous emphysema is linked to postoperative discomfort and respiratory compromise, its reduced occurrence may indirectly underscore the ergonomic benefits of the hinotori platform and its positive influence on patient recovery and comfort.

However, this difference does not necessarily indicate the superiority of one robotic platform over the other. In Japan, hospital reimbursement is largely governed by the Diagnosis Procedure Combination (DPC) system, a case-mix classification and bundled payment model designed to optimize healthcare resource utilization [17]. DPC implementation has been shown to influence hospital management, often incentivizing shorter lengths of stay to align with reimbursement policies [18]. Our institution, established in 2020 as a branch of Fujita Health University Hospital, initially operated under a different reimbursement framework before adopting DPC. During the period when most group D procedures were performed, administrative priorities were focused on maintaining bed occupancy, which may have prolonged hospital stays. These systemic and institutional factors likely contributed to the observed differences in length of stay, independent of the robotic system employed. Future studies should account for such contextual variables—including reimbursement structures—when comparing outcomes between surgical platforms.

The comparable pathological outcomes, including the number of harvested lymph nodes, distal resection margins, and rates of radial margin positivity, confirm the oncological safety of hinotori relative to the da Vinci system. The equivalent distribution of pathological stages between groups further supports the platforms’ oncological equivalence. These findings suggest that even in its early clinical development, hinotori can achieve results consistent with established standards for minimally invasive rectal cancer surgery.

While the hinotori demonstrates comparable outcomes to the da Vinci, its current design lacks integrated devices such as automated staplers and advanced energy devices, including vessel sealers. However, this limitation is mitigated by the use of alternative methods like the double bipolar method (DBM) [19, 20], which has been widely adopted in robot-assisted surgery. Moreover, DBM has also been effectively utilized in procedures performed with the da Vinci, indicating that this workaround does not substantially compromise surgical outcomes.

These hardware and instrumentation limitations require closer coordination between the surgeon and the assistant, particularly during critical phases such as rectal transection and vessel control. This need for synchronized teamwork may impact workflow efficiency during complex procedures. Future iterations of the hinotori that integrate these devices could enhance procedural autonomy for the console surgeon and improve overall surgical efficiency. Such enhancements would also expand the system’s applicability across a broader range of surgical settings and bolster its competitiveness in robot-assisted surgery. Future research and iterative development should focus on these areas to optimize performance and maximize clinical utility.

This study has several limitations. First, its single-center design may limit the generalizability of our findings to other institutions or patient populations. Second, the relatively small sample size—particularly in group H—may have reduced the statistical power to detect subtle differences. Third, our focus on short-term outcomes leaves long-term oncological results, such as survival rates, unaddressed. Moreover, the learning curve associated with hinotori use may have influenced operative times and other procedural metrics. Finally, although PSM minimized baseline imbalances, residual confounding from unmeasured variables cannot be excluded. Future studies should overcome these limitations by enrolling larger, multicenter cohorts, assessing long-term outcomes, and evaluating advanced iterations of hinotori to further improve procedural efficiency.

In conclusion, this PSM study demonstrates that the hinotori system delivers short-term safety outcomes comparable to those of the da Vinci system in robot-assisted rectal cancer surgery. Although operative and console times were significantly longer with hinotori, overall clinical safety—including blood loss, conversion rates, and postoperative complications—was similar across platforms. These findings suggest that hinotori may represent a feasible option for selected cases, particularly at centers equipped with both robotic systems. Further research is needed to assess long-term oncological outcomes and to determine how ongoing technological advancements may impact surgical efficiency.

ARTICLE INFORMATION

Conflict of interest

No potential conflict of interest relevant to this article was reported.

Funding

None.

Acknowledgments

The authors thank all participating patients and those who set up the cancer databases.

Author contributions

Conceptualization: H Katsuno; Data curation: H Katsuno, K Morohara, TE, K Matsuo, T Higashiguchi, TK, H Kanai; Formal analysis: H Katsuno, K Morohara, SA; Investigation: K Morohara, H Katsuno, TE, KK, KN, K Matsuo, T Higashiguchi, TK; Methodology: H Katsuno, SA, T Hanai, ZM; Project administration: H Katsuno, K Morohara, ZM; Supervision: T Hanai, ZM, SA; Visualization: H Katsuno, K Morohara; Writing–original draft: H Katsuno; Writing–review & editing: all authors. All authors read and approved the final manuscript.

Fig. 1.

The hinotori Surgical Robot System (Medicaroid Corp). (A) Operation unit: equipped with 4 robotic arms, each with 8 axes of movement to improve surgical precision and flexibility. (B) Surgeon cockpit: includes adjustable viewer and foot pedals for optimal ergonomics. (C) Monitor cart: displays real-time surgical footage for the operating team.

Fig. 2.

Standard port placement and instrument assignment for the hinotori Surgical Robot System (Medicaroid Corp). Four trocars are arranged diagonally from the right lower quadrant to the left upper quadrant. An assistant port is positioned in the right upper quadrant along a line connecting the midpoint between ports 2 and 3 to the pubic symphysis. Instrument configurations for each robotic arm are indicated.

Fig. 3.

Patient positioning and docking orientation for the hinotori Surgical Robot System (Medicaroid Corp). The patient is placed in the lithotomy position with a 15° Trendelenburg and a 10° right-side tilt. The operation unit is positioned on the patient’s left side. Unlike the conventional platform, the robotic arms are not physically docked to the trocars; instead, hinotori employs a manual pivot calibration system to enable docking-free arm alignment.

Table 1.

Patient characteristics before and after PSM

Characteristic	Before PSM (n=266)			After PSM (n=162)
Characteristic	Group D (n=209)	Group H (n=57)	P-value	Group D (n=108)	Group H (n=54)	P-value
Age (yr)	66 (56–74)	67 (60–74)	0.383	69 (62–75)	66 (60–74)	0.329
Sex			0.445			0.497
Male	79 (37.8)	25 (43.9)		41 (38.0)	24 (44.4)
Female	130 (62.2)	32 (56.1)		67 (62.0)	30 (55.6)
Body mass index (kg/m²)	22.4 (20.2–24.8)	22.2 (19.6–24.3)	0.442	21.8 (19.9–23.8)	22.1 (19.6–24.3)	0.708
ASA physical status			0.211			0.664
I	27 (12.9)	4 (7.0)		7 (6.5)	4 (7.4)
II	169 (80.9)	52 (91.2)		95 (88.0)	49 (90.7)
III	13 (6.2)	1 (1.8)		6 (5.6)	1 (1.9)
Multiple primary CRC	15 (7.2)	1 (1.8)	0.206	2 (1.9)	1 (1.9)	>0.999
Tumor distance from AV (cm)	7 (5.5–10)	8.5 (6–12)	0.063	8 (6–12)	8.5 (6–12)	0.718
Tumor size (mm)	40 (25–50)	35 (26–50)	0.550	33 (25–50)	35 (26–45)	0.672
Clinical T category			0.992			0.783
T0	2 (1.0)	0 (0)		2 (1.9)	0 (0)
T1	45 (21.5)	13 (22.8)		26 (24.1)	13 (24.1)
T2	27 (12.9)	7 (12.3)		14 (13.0)	6 (11.1)
T3	104 (49.8)	30 (52.6)		53 (49.1)	30 (55.6)
T4	31 (14.8)	7 (12.3)		13 (12.0)	5 (9.3)
Clinical N category			0.178			0.867
N0	115 (55.0)	26 (45.5)		55 (50.9)	26 (48.1)
N1	58 (27.8)	18 (31.6)		33 (30.6)	17 (31.5)
N2	25 (11.9)	12 (21.1)		14 (13.0)	10 (18.5)
N3	11 (5.3)	1 (1.8)		6 (5.6)	1 (1.9)
Clinical stage			0.852			0.950
Stage 0	2 (1.0)	0 (0)		2 (1.9)	0 (0)
Stage I	64 (30.5)	17 (29.8)		35 (32.4)	17 (31.5)
Stage II	48 (23.0)	9 (15.8)		17 (15.7)	9 (16.7)
Stage III	79 (37.8)	27 (47.4)		46 (42.6)	25 (46.3)
Stage IV	16 (7.7)	4 (7.0)		8 (7.4)	3 (5.6)
Neoadjuvant chemotherapy	13 (6.2)	3 (5.3)	>0.999	4 (3.7)	2 (3.7)	>0.999

Values are presented as number (%) or median (interquartile range). Group D, patients who underwent robot-assisted surgery for rectal neoplasm with the da Vinci Surgical System (Intuitive Surgical). Group H, patients who underwent robot-assisted surgery for rectal neoplasm with the hinotori Surgical Robot System (Medicaroid Corp).

PSM, propensity score matching; ASA, American Society of Anesthesiologists; CRC, colorectal cancer; AV, anal verge;

Table 2.

Short-term surgical outcomes in propensity score–matched groups

Outcome	Group D (n=108)	Group H (n=54)	P-value
Operative time (min)	227 (178–312)	266 (214–330)	0.014^*
Console time (min)	110 (88–184)	156 (122–205)	0.001^*
Time from incision to console activation (min)	16 (14–23)	20 (16–28)	0.013^*
Blood loss (mL)	14.5 (9–23)	15 (10–34)	0.563
Blood transfusion	1 (0.9)	0 (0)	>0.999
Conversion to laparotomy	0 (0)	0 (0)	NA
Overall complication	15 (13.9)	5 (9.3)	0.458
Clavien-Dindo classification			0.926
I	2 (1.9)	1 (1.9)
II	8 (7.4)	3 (5.6)
IIIa	1 (0.9)	0 (0)
IIIb	4 (3.7)	1 (1.9)
Length of postoperative hospital stay (day)	14 (11–18)	11 (10–13)	0.002^*
Readmission within 30 days after surgery	1 (0.9)	0 (0)	0.892

Values are presented as median (interquartile range) or number (%). Group D, patients who underwent robot-assisted surgery for rectal neoplasm with the da Vinci Surgical System (Intuitive Surgical). Group H, patients who underwent robot-assisted surgery for rectal neoplasm with the hinotori Surgical Robot System (Medicaroid Corp).

NA, not applicable (no events occurred in either group).

^*P<0.05.

Table 3.

Pathological findings in propensity score–matched groups

Variable	Group D (n=108)	Group H (n=54)	P-value
Histological grade			>0.999
G1–2^a	105 (97.2)	53 (98.1)
G3^b	3 (2.8)	1 (1.9)
Lymphatic invasion	69 (63.9)	34 (63.0)	0.862
Vascular invasion	70 (64.8)	37 (68.5)	0.859
Lymph node retrieval	21 (15–28)	21 (13–27)	0.355
Distal margin (mm)	25 (20–45)	30 (15–60)	0.293
Radial margin positivity	1 (0.9)	0 (0)	>0.999
Pathological stage			0.279
Stage 0	8 (7.4)	2 (3.7)
Stage I	24 (22.2)	19 (35.2)
Stage II	18 (16.7)	11 (20.4)
Stage III	48 (44.4)	18 (33.3)
Stage IV	10 (9.3)	4 (7.5)

^aPapillary or tubular adenocarcinoma (well to moderately differentiated).

^bMucinous or poorly differentiated adenocarcinomas.

REFERENCES

1. Feng Q, Yuan W, Li T, Tang B, Jia B, Zhou Y, et al. Robotic versus laparoscopic surgery for middle and low rectal cancer (REAL): short-term outcomes of a multicentre randomised controlled trial. Lancet Gastroenterol Hepatol 2022;7:991–1004. Article PubMed
2. Jayne D, Pigazzi A, Marshall H, Croft J, Corrigan N, Copeland J, et al. Effect of robotic-assisted vs conventional laparoscopic surgery on risk of conversion to open laparotomy among patients undergoing resection for rectal cancer: the ROLARR randomized clinical trial. JAMA 2017;318:1569–80. Article PubMed PMC
3. Park JS, Lee SM, Choi GS, Park SY, Kim HJ, Song SH, et al. Comparison of laparoscopic versus robot-assisted surgery for rectal cancers: the COLRAR randomized controlled trial. Ann Surg 2023;278:31–8. Article PubMed
4. Yang H, Zhou L. The urinary and sexual outcomes of robot-assisted versus laparoscopic rectal cancer surgery: a systematic review and meta-analysis. Surg Today 2024;54:397–406. Article PubMed PDF
5. Matsuyama T, Endo H, Yamamoto H, Takemasa I, Uehara K, Hanai T, et al. Outcomes of robot-assisted versus conventional laparoscopic low anterior resection in patients with rectal cancer: propensity-matched analysis of the National Clinical Database in Japan. BJS Open 2021;5:zrab083.Article PubMed PMC PDF
6. Kim HJ, Choi GS, Park JS, Park SY, Yang CS, Lee HJ. The impact of robotic surgery on quality of life, urinary and sexual function following total mesorectal excision for rectal cancer: a propensity score-matched analysis with laparoscopic surgery. Colorectal Dis 2018;20:O103–13. Article PubMed PDF
7. Park EJ, Cho MS, Baek SJ, Hur H, Min BS, Baik SH, et al. Long-term oncologic outcomes of robotic low anterior resection for rectal cancer: a comparative study with laparoscopic surgery. Ann Surg 2015;261:129–37. Article PubMed
8. Katsuno H, Morohara K, Endo T, Chikaishi Y, Kikuchi K, Nakamura K, et al. A new era in surgical oncology: preliminary insights into the hinotori™ surgical robot system’s role in rectal surgery using the double bipolar method. World J Surg Oncol 2024;22:215.Article PubMed PMC PDF
9. Miura R, Okuya K, Akizuki E, Miyo M, Noda A, Ishii M, et al. World-first report of low anterior resection for rectal cancer with the hinotori™ Surgical Robot System: a case report. Surg Case Rep 2023;9:156.Article PubMed PMC PDF
10. Motoyama D, Matsushita Y, Watanabe H, Tamura K, Otsuka A, Fujisawa M, et al. Perioperative outcomes of robot-assisted partial nephrectomy using hinotori versus da Vinci surgical robot system: a propensity score-matched analysis. J Robot Surg 2023;17:2435–40. Article PubMed PDF
11. Kohjimoto Y, Yamashita S, Iwagami S, Muraoka S, Wakamiya T, Hara I. hinotori^TM vs. da Vinci^®: propensity score-matched analysis of surgical outcomes of robot-assisted radical prostatectomy. J Robot Surg 2024;18:130.Article PubMed PDF
12. Katsuno H, Maeda K, Hanai T, Masumori K, Matsuoka H, Uyama I, et al. A novel approach of robot surgery for colorectal cancer. Jpn J Gastroenterol Surg 2010;43:1002–6. Japanese. Article
13. Japanese Society for Cancer of the Colon and Rectum. Japanese classification of colorectal, appendiceal, and anal carcinoma: the 3d English edition [secondary publication]. J Anus Rectum Colon 2019;3:175–95. Article PubMed PMC
14. Nakauchi M, Suda K, Nakamura K, Tanaka T, Shibasaki S, Inaba K, et al. Establishment of a new practical telesurgical platform using the hinotori™ Surgical Robot System: a preclinical study. Langenbecks Arch Surg 2022;407:3783–91. Article PubMed PMC PDF
15. Austin PC. A comparison of 12 algorithms for matching on the propensity score. Stat Med 2014;33:1057–69. Article PubMed PDF
16. Kumamoto T, Otsuka K, Hiro J, Taniguchi H, Cheong Y, Omura Y, et al. Impact of the new robotic platform hinotori™ in preventing subcutaneous emphysema after colorectal cancer surgery. Surg Endosc 2025;39:229–36. Article PubMed PDF
17. Shigemi D, Morishima T, Yamana H, Yasunaga H, Miyashiro I. Validity of initial cancer diagnoses in the Diagnosis Procedure Combination data in Japan. Cancer Epidemiol 2021;74:102016.Article PubMed
18. Murata A, Okamoto K, Muramatsu K, Matsuda S. Endoscopic submucosal dissection for gastric cancer: the influence of hospital volume on complications and length of stay. Surg Endosc 2014;28:1298–306. Article PubMed PDF
19. Katsuno H, Hanai T, Endo T, Morise Z, Uyama I. The double bipolar method for robotic total mesorectal excision in patients with rectal cancer. Surg Today 2022;52:978–85. Article PubMed PDF
20. Kikuchi K, Suda K, Shibasaki S, Tanaka T, Uyama I. Challenges in improving the minimal invasiveness of the surgical treatment for gastric cancer using robotic technology. Ann Gastroenterol Surg 2021;5:604–13. Article PubMed PMC PDF

Figure & Data

References

Citations

Citations to this article as recorded by

Racing toward the future of robot-assisted rectal cancer surgery: a comparative study of hinotori and da Vinci
Sung Uk Bae
Annals of Coloproctology.2025; 41(4): 259. CrossRef

Cite this Article

Cite this Article: export Copy Download Format; Close

Download Citation

Download a citation file in RIS format that can be imported by all major citation management software, including EndNote, ProCite, RefWorks, and Reference Manager.

Format:

RIS — For EndNote, ProCite, RefWorks, and most other reference management software
BibTeX — For JabRef, BibDesk, and other BibTeX-specific software

Include:

Citation for the content below
Citation and abstract for the content below

Propensity score–matched comparison of robot-assisted rectal cancer surgery using hinotori and da Vinci

Ann Coloproctol. 2025;41(4):310-318. Published online August 25, 2025

DOI: https://doi.org/10.3393/ac.2025.00136.0019

XML Download

Figure

Related articles

Propensity score–matched comparison of robot-assisted rectal cancer surgery using hinotori and da Vinci

Fig. 1. The hinotori Surgical Robot System (Medicaroid Corp). (A) Operation unit: equipped with 4 robotic arms, each with 8 axes of movement to improve surgical precision and flexibility. (B) Surgeon cockpit: includes adjustable viewer and foot pedals for optimal ergonomics. (C) Monitor cart: displays real-time surgical footage for the operating team.

Fig. 2. Standard port placement and instrument assignment for the hinotori Surgical Robot System (Medicaroid Corp). Four trocars are arranged diagonally from the right lower quadrant to the left upper quadrant. An assistant port is positioned in the right upper quadrant along a line connecting the midpoint between ports 2 and 3 to the pubic symphysis. Instrument configurations for each robotic arm are indicated.

Fig. 3. Patient positioning and docking orientation for the hinotori Surgical Robot System (Medicaroid Corp). The patient is placed in the lithotomy position with a 15° Trendelenburg and a 10° right-side tilt. The operation unit is positioned on the patient’s left side. Unlike the conventional platform, the robotic arms are not physically docked to the trocars; instead, hinotori employs a manual pivot calibration system to enable docking-free arm alignment.

Graphical abstract

Fig. 1.

Fig. 2.

Fig. 3.

Graphical abstract

Propensity score–matched comparison of robot-assisted rectal cancer surgery using hinotori and da Vinci

Characteristic	Before PSM (n=266)			After PSM (n=162)
Characteristic	Group D (n=209)	Group H (n=57)	P-value	Group D (n=108)	Group H (n=54)	P-value
Age (yr)	66 (56–74)	67 (60–74)	0.383	69 (62–75)	66 (60–74)	0.329
Sex			0.445			0.497
Male	79 (37.8)	25 (43.9)		41 (38.0)	24 (44.4)
Female	130 (62.2)	32 (56.1)		67 (62.0)	30 (55.6)
Body mass index (kg/m²)	22.4 (20.2–24.8)	22.2 (19.6–24.3)	0.442	21.8 (19.9–23.8)	22.1 (19.6–24.3)	0.708
ASA physical status			0.211			0.664
I	27 (12.9)	4 (7.0)		7 (6.5)	4 (7.4)
II	169 (80.9)	52 (91.2)		95 (88.0)	49 (90.7)
III	13 (6.2)	1 (1.8)		6 (5.6)	1 (1.9)
Multiple primary CRC	15 (7.2)	1 (1.8)	0.206	2 (1.9)	1 (1.9)	>0.999
Tumor distance from AV (cm)	7 (5.5–10)	8.5 (6–12)	0.063	8 (6–12)	8.5 (6–12)	0.718
Tumor size (mm)	40 (25–50)	35 (26–50)	0.550	33 (25–50)	35 (26–45)	0.672
Clinical T category			0.992			0.783
T0	2 (1.0)	0 (0)		2 (1.9)	0 (0)
T1	45 (21.5)	13 (22.8)		26 (24.1)	13 (24.1)
T2	27 (12.9)	7 (12.3)		14 (13.0)	6 (11.1)
T3	104 (49.8)	30 (52.6)		53 (49.1)	30 (55.6)
T4	31 (14.8)	7 (12.3)		13 (12.0)	5 (9.3)
Clinical N category			0.178			0.867
N0	115 (55.0)	26 (45.5)		55 (50.9)	26 (48.1)
N1	58 (27.8)	18 (31.6)		33 (30.6)	17 (31.5)
N2	25 (11.9)	12 (21.1)		14 (13.0)	10 (18.5)
N3	11 (5.3)	1 (1.8)		6 (5.6)	1 (1.9)
Clinical stage			0.852			0.950
Stage 0	2 (1.0)	0 (0)		2 (1.9)	0 (0)
Stage I	64 (30.5)	17 (29.8)		35 (32.4)	17 (31.5)
Stage II	48 (23.0)	9 (15.8)		17 (15.7)	9 (16.7)
Stage III	79 (37.8)	27 (47.4)		46 (42.6)	25 (46.3)
Stage IV	16 (7.7)	4 (7.0)		8 (7.4)	3 (5.6)
Neoadjuvant chemotherapy	13 (6.2)	3 (5.3)	>0.999	4 (3.7)	2 (3.7)	>0.999

Outcome	Group D (n=108)	Group H (n=54)	P-value
Operative time (min)	227 (178–312)	266 (214–330)	0.014^*
Console time (min)	110 (88–184)	156 (122–205)	0.001^*
Time from incision to console activation (min)	16 (14–23)	20 (16–28)	0.013^*
Blood loss (mL)	14.5 (9–23)	15 (10–34)	0.563
Blood transfusion	1 (0.9)	0 (0)	>0.999
Conversion to laparotomy	0 (0)	0 (0)	NA
Overall complication	15 (13.9)	5 (9.3)	0.458
Clavien-Dindo classification			0.926
I	2 (1.9)	1 (1.9)
II	8 (7.4)	3 (5.6)
IIIa	1 (0.9)	0 (0)
IIIb	4 (3.7)	1 (1.9)
Length of postoperative hospital stay (day)	14 (11–18)	11 (10–13)	0.002^*
Readmission within 30 days after surgery	1 (0.9)	0 (0)	0.892

Variable	Group D (n=108)	Group H (n=54)	P-value
Histological grade			>0.999
G1–2^a	105 (97.2)	53 (98.1)
G3^b	3 (2.8)	1 (1.9)
Lymphatic invasion	69 (63.9)	34 (63.0)	0.862
Vascular invasion	70 (64.8)	37 (68.5)	0.859
Lymph node retrieval	21 (15–28)	21 (13–27)	0.355
Distal margin (mm)	25 (20–45)	30 (15–60)	0.293
Radial margin positivity	1 (0.9)	0 (0)	>0.999
Pathological stage			0.279
Stage 0	8 (7.4)	2 (3.7)
Stage I	24 (22.2)	19 (35.2)
Stage II	18 (16.7)	11 (20.4)
Stage III	48 (44.4)	18 (33.3)
Stage IV	10 (9.3)	4 (7.5)

Table 1. Patient characteristics before and after PSM

PSM, propensity score matching; ASA, American Society of Anesthesiologists; CRC, colorectal cancer; AV, anal verge;

Table 2. Short-term surgical outcomes in propensity score–matched groups

NA, not applicable (no events occurred in either group).

P<0.05.

Table 3. Pathological findings in propensity score–matched groups

Papillary or tubular adenocarcinoma (well to moderately differentiated).

Mucinous or poorly differentiated adenocarcinomas.