Surgical Endoscopy
https://doi.org/10.1007/s00464-024-10695-0

and Other Interventional Techniques

DYNAMIC MANUSCRIPTFirst clinical experiences of robotic gastrectomy for gastric cancer
using the hinotori™ surgical robot system
Seiji Inoue1 · Masaya Nakauchi2 · Yusuke Umeki1 · Kazumitsu Suzuki1 · Akiko Serizawa1 · Shingo Akimoto1 ·Yusuke Watanabe2 · Tsuyoshi Tanaka1 · Susumu Shibasaki1 · Kazuki Inaba2 · Ichiro Uyama2,3 · Koichi Suda1,4Received: 19 November 2023 / Accepted: 2 January 2024
© The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024

Abstract
Background Although the da Vinci™ Surgical System is the most predominantly used surgical robot worldwide, other surgical robots are being developed. The Japanese surgical robot hinotori™ Surgical Robot System was launched and approvedfor clinical use in Japan in November 2022. We performed the first robotic gastrectomy for gastric cancer using hinotoriin the world. Here, we report our initial experience and evaluation of the feasibility and safety of robotic gastrectomy for
gastric cancer using hinotori.
Methods A single-institution retrospective study was conducted. Between November 2022 and October 2023, 24 patientswith gastric cancer underwent robotic gastrectomy with hinotori. Five ports, including one for an assistant, were placed in
the upper abdomen, and gastric resection with standard lymphadenectomy and intracorporeal reconstruction were performed.
The primary endpoint was the postoperative complication rate within 30 days after surgery. The secondary outcomes were
surgical outcomes, including intraoperative adverse events, operative time, blood loss, and the number of dissected nodes.
Results Of the 24 patients, 16 (66.7%) were male. The median age and body mass index were 73.5 years and 22.9 kg/m2,
respectively. Twenty-three patients (95.8%) had tumors in the middle to lower stomach. Sixteen (66.7%) and seven (29.2%)
patients had clinical stage I and II diseases, respectively. Twenty-three (95.8%) patients underwent distal gastrectomy. No
patient had postoperative complications of Clavien–Dindo classification IIIa or higher, whereas two (8.3%) had the grade IIcomplications (enteritis and pneumonia). No intraoperative adverse events, including conversion to other approaches, wereobserved. All patients received R0 resection. The median operative and console times were 400 and 305 min, respectively.
The median blood loss was 14.5 mL, and the number of lymph nodes dissected was 51.5.
Conclusions This study found that robotic gastrectomy with standard lymphadenectomy for gastric cancer using hinotori
can be safely performed.
Keywords Gastrectomy · Lymphadenectomy · Gastric Cancer · Robotic surgical procedure* Masaya Nakauchi
naka57ma38@hotmail.com
1

Department of Surgery, Fujita Health University, Toyoake,
Japan

2

Department of Advanced Robotic and Endoscopic Surgery,Fujita Health University, 1‑98 Dengakugakubo, Kutsukake,Toyoake, Aichi 470‑1192, Japan

3

Collaborative Laboratory for Research and Developmentin Advanced Surgical Technology, Fujita Health University,
Toyoake, Japan

4

Collaborative Laboratory for Research and Developmentin Advanced Surgical Intelligence, Fujita Health University,
Toyoake, Japan

Abbreviations
RG	Robotic gastrectomy
da Vinci	da Vinci™ surgical system
RCTs	Randomized controlled trials
hinotori	hinotori™ surgical robot system
JGCA​	Japan Gastric Cancer Association
JSES	Japanese Society of Endoscopic Surgery
C–D	Clavien–Dindo
Gastric cancer is a common cancer and a leading causeof cancer-related death [1]. Although the development ofchemotherapy has increased the use of multidisciplinary
treatment, including preoperative, postoperative, and perioperative treatments, R0 resection with lymphadenectomy
Vol.:(0123456789)

Surgical Endoscopy

is a mainstream curative treatment [2]. Minimally invasive
surgery, including laparoscopic and robotic approaches, isbecoming more common in the surgical treatment of gastric cancer due to advances in surgical technologies since
the first robotic gastrectomy (RG) for gastric cancer was
reported in 2003 [3]. The da Vinci™ Surgical System (daVinci, Intuitive Surgical Inc. CA) is the most predominantsurgical robot worldwide and features tremor reduction,
articulated forceps, and a three-dimensional (3D) magnified
scope, which can overcome the motion limit in conventional
laparoscopy. In fact, several studies, including randomized
controlled trials (RCTs), have proven the benefits of RG overconventional laparoscopic and open approaches. Based on
this evidence, the Japanese government approved robotic
surgery for three gastrointestinal cancers, including gastriccancer, under the national medical insurance coverage in2018 [4]. Subsequently, robotic surgery has rapidly spreadnationwide. However, as previously reported, one of thedisadvantages of robotic surgery is its high cost, which has
become a major problem because the number of robotic surgeries performed has increased [5]. The da Vinci has dominated the robotic surgery field since its launch in 1999, andanother surgical robot has been expected to appear.
In 2020, a new Japanese surgical robot was launched,
named the hinotori™ Surgical Robot System (hinotori). This
made-in-Japan surgical robot was developed by Medicaroid
Inc. (Kobe, Japan), which was established in 2013 as a joint
venture between Kawasaki Heavy Industries, Ltd. (Tokyo,
Japan) and Sysmex Corporation (Kobe, Japan). During thedevelopment of this system, “compactness,” “safety,” and“maneuverability” were emphasized. This system became
the first robot-assisted surgery system created in Japan togain Japanese regulatory approval in August 2020. In theFig. 1  The hinotori Surgical
Robot System. A surgical cockpit in which a console surgeon
can adjust the position of theviewer and foot pedals (a). An
operation unit with four instruments, including a scope (b),four manipulating arms witheight axes without attaching the
trocar (c, d). A 2 K 16:9 wide
monitor (e)urology field, the first human surgery using hinotori was
successfully performed in December 2020 [6]. Gastrectomy
using hinotori was approved by the Japanese government inNovember 2022.
We started RG using da Vinci in 2009 and have performed more than 800 RGs for gastric cancer. Furthermore,
we reported that RG provided better surgical and comparable
oncological outcomes than the conventional laparoscopic
approach [7–10]. We introduced hinotori to our institution in2020 and validated the gastrectomy procedure using hinotori
in dry, cadaver, and animal models [11]. After its approval
for clinical use in 2022, we performed the first RG for gastriccancer using hinotori in November 2022. This study aimed
to evaluate the feasibility and safety of RG for gastric cancer
using hinotori.

Methods
hinotori™ surgical robot system
Similar to da Vinci, hinotori consists of an operation unit
with four arms and a surgeon cockpit (Fig. 1a, b). As points
differing from the da Vinci, first, each robotic arm has eightaxes that enable more flexible arm movement and reduce theinterference between the arms and between the arm and thepatient's body (Fig. 1c). Furthermore, the system monitors
the distance between each arm, and an alarm is issued whenpotential interference occurs. Second, the software calibrates
the fulcrum position of the trocar and instrument, which isnamed pivot position and similar to the remote center in daVinci, without attaching the trocar and robotic arm (docking-free system) (Fig. 1d), which can provide a large spaceSurgical Endoscopy

around the trocars and prevent tissue damage to the abdominal wall by excessive traction. Third, the surgeon cockpit hasa flexibly positioned 3D viewer that can reduce fatigue of thesurgeon’s neck and shoulder (Fig. 1a). Fourth, hinotori uses
a 16:9 wide monitor, allowing a wider field of view at a time,
whereas da Vinci uses a 4:3 monitor (Fig. 1e).

Patients
Demographic, clinicopathological, and treatment data werecollected from the prospectively maintained surgical gastriccancer database and electronic medical records at our institution. Considering the safety of hinotori during the introductory phase, this study indicated hinotori for patients withclinical stage I or II gastric cancer for the first five cases, andpatients receiving preoperative chemotherapy were considered contraindicated for hinotori. Between November 2nd,2022, and October 5th, 2023, 111 patients with pathologically confirmed gastric cancer were indicated for surgicalresection. They were evenly offered hinotori, other robotic
approaches including da Vinci, conventional laparoscopic,
or open approaches. Then, consecutive 24 patients who
agreed to undergo surgery with hinotori were included inthis study. Of the remaining 87 patients, 75 underwent otherrobotic gastrectomy. Clinical and pathological tumor depth(T stage), lymph node status (N stage), and TNM stage wereclassified according to the 6th edition of the Japan Gastric
Cancer Association (JGCA) classification guidelines [2].
Our previous reports detailed the indications for physicalfunction assessment, perioperative management, and postoperative chemotherapy, along with oncological follow-up[7]. Nine console surgeons (IU, KS, SS, MN, TT, KI, KS,
AS, and YU) who experienced > 30 robotic gastrectomies
using da Vinci and were qualified by the Japanese Society ofEndoscopic Surgery (JSES) endoscopic surgical skill qualification system, participated as a console surgeon in thisstudy. Of the nine console surgeons (IU, KS, SS, MN, TT,
KI, KS, AS, and YU), two surgeons who did not participate
in the surgery independently assessed the extent of nodal
dissection using a nonedited video. All patients were treatedaccording to the Declaration of Helsinki, and this singleinstitutional, single-arm, retrospective cohort study was
conducted after obtaining approval from the Fujita Health
University Evaluating Committee for Highly Difficult New
Technologies (approval number 22–06) and Institutional
Review Board (approval number HM18-409).

Position and port placement
The layout of the operation room is shown in Fig. 2a. The
patient was placed in the supine position with the legs apart,and the left arm extended, with a 10–15° head-up tilt. Fivetrocars, including one port for the assistant surgeon, wereplaced in the upper abdomen, and a pneumoperitoneum of
10 cmH2O was started (Fig. 2b, c). The operation unit wasrolled in from the right side (Fig. 3a). Based on our experiences of da Vinci gastrectomy [7], the arm arrangement was
set up to target the splenic hilum to prevent extracorporeal
collision between the robotic arms (Fig. 2b). The arm basewas tilted 8° to the head side. The left–right tilt of the armbase was matched to the left–right tilt of the operation bed
to prevent full extension of the first and fourth robotic arms.
After placing each port, the pivot was set using a pivoter(Fig. 3b). The distance between the pivots was displayed(Fig. 3c).

Devices and surgical procedures
Maryland Bipolar Forceps (Medicaroid Inc., Kobe, Japan) or
Monopolar Curved Scissors (Medicaroid Inc., Kobe Japan),which were connected to an AUTOCON™ II 400 Electrosurgical Unit (KARL STORZ、Tuttlingen, Germany),
and a universal grasp (Medicaroid Inc., Kobe, Japan) wereused using the third and fourth arm of the robot, respectively, whereas Fenestrated Bipolar Forceps (MedicaroidInc., Kobe, Japan) was used using the first arm of the robot(Fig. 4). The details of the surgical procedure have beenpreviously reported [7, 12, 13]. In summary, the extent ofgastrectomy and lymph node dissection was determinedaccording to the JGCA treatment guidelines [2]. Lymphnode dissection was performed using the outermost layeroriented approach [12, 13]. For patients with cT1N0 diseases, D1 + lymph node dissection, including perigastriclymph nodes and those along the celiac trunk, left gastric,
and common and proper hepatic arteries, were performed.
For patients with cT ≥ 2 N any diseases, D2 lymph node dissection, including lymph nodes along the proximal splenicartery and portal vein, in addition to D1 + lymph nodes, wasperformed (Fig. 5). Intracorporeal Billroth-I or Billroth-II
anastomosis using linear staplers was performed following
distal gastrectomy. Esophagogastrostomy was performed following proximal gastrectomy (Fig. 6). The console surgeons
performed most procedures, excluding port placement andtransection of stomach and duodenum, using linear staplers
by the assistant surgeons. Because the vessel sealing systemand suction-irrigation device are not available in hinotori,
the assistant surgeons used LigaSure (Medtronic Inc, Minneapolis, MN, US) to divide thick tissue and vessels andlaparoscopic suction-irrigation device (LAGIS Enterprise,Taichung, Taiwan).

Measurements and statistical analyses
All patients were observed for at least 30 days after surgery. The primary endpoint was postoperative complication
rates within 30 days after surgery. The secondary endpoints

Surgical Endoscopy

Fig. 2  Operation room equipment layout (a). Port placement (b). The
1st arm port (R1) was placed at the right abdomen and 3 cm caudal
to the gallbladder. The fourth arm port (R4) The ports for robot arms
(R1-4) were placed at the left abdomen, in line with the bottom lineof the greater curvature. The assistant port (As) was placed between
R1 and R2. The distances between each port are shown in the figure.
The arm base was rotated toward the splenic hilum (red arrow). Theview after port placement (c)were short-term outcomes, including operative time, console time, blood loss, conversion to other approaches, thenumber of dissected nodes, and postoperative hospital stay.
All grade II or higher postoperative complications classified according to the Clavien–Dindo (CD) classification[14] were recorded. The total operative time was defined as
the duration from the start of abdominal incision to woundclosure completion, and the console time was defined as theduration of the hinotori operation during surgery, including the time required to extract the resected specimen fromthe umbilical incision and to redock for the reconstruction.
Blood loss was estimated by weighing suctioned blood andgauze pieces that had absorbed blood. Categorical variables
are expressed as numbers and percentages. Continuous variables are expressed as medians and ranges. All analyses were
performed using Statistical Package for the Social Sciences,version 28.0 (IBM Corp., Armonk, NY, USA).

16.7–28.6 kg/m 2), respectively. Twenty-three (95.8%)
patients had tumors in the middle to lower stomach. Sixteen (66.7%) and seven (29.2%) patients had clinical stage
I and II diseases, respectively. The surgical outcomes areshown in Table 2. Of the 24 patients, 23 (95.8%) and nine
(37.5%) underwent distal gastrectomy and D2 lymph
node dissection, respectively. No intraoperative adverse
events or conversion to other approaches were observed.
The total operative and console times were 400 min(range, 281–515 min) and 305 min (range, 214–429 min),respectively. The median blood loss was 14.5 mL (range,
5–113 mL). Pathological and postoperative outcomes areshown in Table 3. Postoperative complications of any CD
grade and CD grade II were observed in five (20.8%) andtwo (8.3%) patients, respectively. None of the patients had
CD grade IIIa or higher complications. No reoperationor surgical mortality was observed. All patients underwent R0 resection. The median number of lymph nodes
retrieved was 51.5 (range, 30–90), and the length of postoperative hospital stay was 11 days (range, 8–25 days).
None of the patients were readmitted within 30 days after
discharge. The video review confirmed the completionof scheduled gastrectomy with lymphadenectomy in all
patients. The operation video is shown in Supplemental
Video 1.

Results
The clinicopathological characteristics of the patients areshown in Table 1. Of the 24 patients, 16 (66.7%) weremale, and the median age and body mass index were
73.5 years (range, 48–88 years) and 22.9 kg/m2 (range,

Surgical Endoscopy

Fig. 3  The operation unit was rolled in (a). Pivoting using a pivoter (b). The distance between the pivots was displayed (c)Discussion
This study found that RG with standard lymphadenectomy
for gastric cancer using hinotori could be safely performed.
To the best of our knowledge, this is the first study to report
the clinical use of hinotori for gastric cancer surgery. No
complications of CD grade IIIa or higher occurred in thisstudy, whereas complications of CD grade II were observedin 8.3% of the patients. In RG using da Vinci for gastriccancer, the morbidity rates have been reported to range from
1.3 to 5.3% for CD grade IIIa or higher complications andfrom 8.8 to 9.2% for CD grade II or higher complications
in several studies, including RCT and our previous studies[5, 15–19]. Furthermore, the operative time, blood loss, andnumber of dissected nodes in this study appeared to be similar to those reported in previous studies [15, 16]. Although
this study excluded patients receiving neoadjuvant chemotherapy and patients with high advanced diseases, this study
with at least comparable short-term outcomes demonstrated
that RG for gastric cancer using hinotori could be safely
introduced into clinical practice.
Although the basic structure of hinotori is similar
to that of da Vinci in terms of the number of arms andhow they are operated, hinotori is not equipped with anadvanced energy device, such as a vessel sealing system and ultrasonic coagulating sears, as of October 2023
because hinotori was launched recently. Therefore, in thisseries, the assistant surgeons partially helped perform theSurgical Endoscopy

Fig. 4  Instruments available in hinotoriFig. 5  D2 nodal dissection during distal gastrectomy. In the suprapancreatic lymph nodes (LNs) dissection, the left gastric artery(LGA) was divided at its root. a, the #8a LNs (anterosuperior LNs
along the common hepatic artery (CHA)) and #12a LNs (hepatoduodenal ligament LNs along the proper hepatic artery (PHA)) were dissected. PV, portal vein; Panc, pancreas. b, the #11p LNs (Proximal

splenic artery (SPA) LNs) and the left side of #9 LNs (Celiac artery
LNs) were dissected. SPV, splenic vein (c), mobilization of the mesocolon and preparation of the infrapyloric LNs dissection, RGEV, right
gastroepiploic vein (d), the final view after LNs dissection of thesuprapancreatic area (e) and infrapyloric area, RGEV, right gastroepiploic vein (f)procedures using a vessel sealing system to divide lymphatic and blood vessels, whereas we mainly used bipolar
forceps as energy devices, as with the da Vinci procedure (double bipolar technique [7]). Such collaboration
between console and assistant surgeons could save timeexchanging robotic instruments. Therefore, the operative
time might appear similar to that reported in previous publications, irrespective of the introductory nature of thisstudy. Evaluating the benefits of such collaborative robotic
surgery in hinotori by accumulating more cases is necessary. However, the assistant surgeon’s forceps are linear,and their tremor cannot be reduced to zero. The assistantsurgeon was also required to have a certain degree ofminimally invasive surgical skill. A major advantage
of surgical robots is that they overcome the limitationsof forceps movement and hand tremors in conventional
laparoscopic surgery. To maximize the benefits of surgical robots, developing at least vessel sealing devices forhinotori is urgently needed. In other fields, hinotori procedures have been rapidly expanding in Japan. Case reportsof distal pancreatectomy for pancreatic cancer [20] andright hemicolectomy for colon cancer [21] and case seriesof six adrenectomies [22], 11 total hysterectomies [23],and 30 partial nephrectomies [24] have been published.

Surgical Endoscopy

Fig. 6  Intracorporeal Billroth-II anastomosis (a–c) and Billroth-I anastomosis (d–f) using linear staplers

Table 1  Patients’ demographic
and clinical characteristics

Case

Age

Sex

BMI

ASA

Location

Histology

DifferentiationcTN stage

cStage

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24

75
60
60
63
69
68
48
65
79
63
88
72
81
78
75
79
65
77
64
83
78
85
79
71

F
F
M
M
M
M
F
M
M
M
M
F
M
F
F
M
M
F
M
M
M
F
M
M

20.8
19.6
19.5
17.1
25.0
28.6
19.7
27.6
22.8
24.5
23.3
21.1
20.4
16.7
23.6
20.5
23.2
23.5
25.2
22.2
22.0
23.9
24.0
23.0

2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
3
3
2
1
1
3
2
2
2

M
M
M
M
M
M
U
M
M
M
M
M
M
L
M
M
M
M
L
M
L
L
M
M

tub
por/sig
tub
por/sig
tub
tub
por
tub
tub
por
por
tub
por
tub
por/sig
tub
por
por
tub
tub
por
tub
tub
tub

Well
Poor
Well
Poor
Well
Well
Mod
Mod
Poor
Poor
Mod
Mod
Poor
Mod
Poor
Well
Poor
Poor
Well
Mod
Poor
Mod
Mod
Mod

T3N−
T1bN−
T2N−
T1bN−
T1bN−
T1bN−
T2N−
T1bN−
T1bN−
T1bN−
T3N−
T1bN−
T3N +
T3N−
T2N +
T1bN−
T1bN−
T3N−
T1bN−
T1bN−
T3N−
T1bN−
T1bN−
T3N−

IIB
I
I
I
I
I
I
I
I
I
IIB
I
III
IIB
IIA
I
I
IIB
I
I
IIB
I
I
IIB

ASA American Society of Anesthesiologists physical status; M male; F female, U upper stomach; M middle
stomach; L lower stomach

Accumulating such clinical experiences will help Medicaroid update hinotori and develop new devices that will fully
exploit the inherent advantages of the surgical robot—not
only tremor reduction and instrument articulation but

also collecting surgical intelligence, including operating
surgeons’ log information—when they appear in the near
future [11].

Surgical Endoscopy
Table 2  Surgical outcomes
Case

Operator

Type of gastrectomy

Lymphadenectomy

Reconstruction

Operative time

Console time

Blood loss

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24

1
2
2
1
3
4
2
2
3
1
4
3
4
3
1
4
5
6
6
7
3
7
8
9

DistalDistalDistalDistalDistalDistalProximal
DistalDistalDistalDistalDistalDistalDistalDistalDistalDistalDistalDistalDistalDistalDistalDistalDistal

D2
D1 +
D2
D1 +
D1 +
D1 +
D2
D1 +
D1 +
D1 +
D1 +
D1 +
D2
D2
D2
D1 +
D1 +
D2
D1 +
D1 +
D2
D1 +
D1 +
D2

B-I
B-I
B-I
B-II
B-II
B-II
Esophago-gastric
B-I
B-I
B-I
B-II
B-II
B-II
B-I
B-II
B-II
B-II
B-I
B-I
B-II
B-I
B-I
B-I
B-II

425
303
332
354
400
508
464
444
400
295
409
300
394
315
506
406
373
460
515
395
281
449
394
478

382
215
244
232
294
334
308
342
293
245
310
214
304
228
380
305
264
355
337
292
225
357
335
429

30
5
5
6
12
86
14
113
7
35
9
15
25
7
12
28
10
11
112
16
15
5
45
53

B-I Billroth I; B-II Billroth II

In terms of the setting, based on our experience withda Vinci, we have reported the usefulness of “da Vinci’splane” theory and appropriate port-to-port distances to prevent extracorporeal collision between arms and the “monitor quadrisection” theory to prevent intracorporeal collision
between instruments [7]. In the present study, we followed
these theories and found no intraoperative collision or otheradverse events, indicating that these theories are equallyimportant in hinotori. Regarding the features of hinotorithat differ from those of da Vinci, the docking-free system
displays the distance between the set pivot points, allowing
for intraoperative pivot adjustment, which was very useful inflexibly accommodating patients with various body shapes
and establishing a highly reproducible setup. Furthermore,because the arm and port are not fixed, excessive force is
not applied to the abdominal wall, which is expected toreduce the possibility of damage to the abdominal wall. On
the other hand, this docking-free system requires caution inpatients with high BMI. It is sometimes quite challenging
to obtain a clear view during the suprapancreatic dissection in patients with high visceral fat. Unlike da Vinci, thescope trocar cannot be forcibly repositioned after docking

in hinotori, so the scope trocar must be set strictly at 15 cm
from the xiphoid process, regardless of the position of theumbilicus. In addition, in patients with high subcutaneousfat, the pivot setting on the body surface may require somemodification, such as setting the pivot in the trocar, because
the pivot set on the body surface and the point of fascial
penetration, which is theoretically ideal, are misaligned.
The 16:9 wide monitor provided a wide field of view, which
helped understand the anatomy and prevent organ injury inthe blind area. The arm with 8-axis joints and collision alarmfunction can help prevent arm collision and unexpected accidents caused by arm collision, which is a major concern inrobotic surgery. In addition, the left–right tilt of the arm baseparallel to the operation bed helped prevent full extensionof the arms. Although these characteristics of hinotori were
not compared with those of da Vinci in detail in this study,
the usefulness of this surgical robot system is expected to
be demonstrated by accumulating more cases in the future.
The hinotori has several issues to be resolved or developed. First, the docking-free system makes the instrument
tip less stable than the da Vinci. An update of the softwareis needed. Second, the collision alarm may help prevent

Surgical Endoscopy
Table 3  Pathological andpostoperative findings

Case

Dissected lymph pTN stage
nodes

pStageHospital stay

Postoperative complications (CD grade)

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24

54
84
85
53
32
32
43
48
30
62
45
58
57
54
90
47
31
61
38
30
46
60
50
69

IIIA
IA
IA
IA
IA
IA
IIB
IA
IA
IB
IIA
IA
IIB
IIIB
IA
IA
IIB
IA
IA
IIA
IIIB
IB
IA
IIIA

25
10
14
11
18
10
18
10
10
11
21
14
10
8
11
11
8
11
9
10
19
10
10
12

Delayed gastric empty (I)
None
None
None
Delayed gastric empty (I)None
Lymphorrhea (I)
None
None
None
Enteritis (II)
None
None
None
None
None
None
None
None
None
Pneumonia (II)
None
None
None

T3N2
T1bN0
T1aN0
T1aN0
T1bN0
T1aN0
T4aN0
T1bN0
T1bN0
T1bN1
T3N0
T1aN0
T3N1
T4aN3a
T1bN0
T1aN0
T3N1
T1bN0
T1bN0
T1bN2
T3N3a
T1bN1
T1bN0
T4aN1

serious accidents, but it also detects minor collisions that thesurgeon can anticipate, and the arm automatically is forced
to stop. The system may make the operation smoother bydetecting the degree of collision and informing the console
surgeon of its risk. Third, one of the features of hinotori isremote surgery. In a preclinical study, we performed gastrectomy in an animal model between two sites approximately
30 km apart using fiber-optic lines and hinotori. And weoperate with sufficient quality under a delay of about 30 ms[11]. Although guidelines need to be developed, hinotori
may be useful for implementing a telesurgery platform withfurther improvements.
Before we performed the first case of RG for gastric cancer in this study, hinotori had only been used in prostate surgery [6]. Because there is no precedent for upper abdominal
surgery, fully validating the setting and detailed proceduresin dry, animal, and cadaver models would be useful [11].
The JSES has established guidelines for the safe introduction of new surgical robots and is constantly revising theseguidelines. The JSES certifies RG proctors with the JSES
Endoscopic Surgical Skill Qualification [25] and experienceof 40 RGs. When a new robot is ready for clinical use in RG,(1) the JSES certifies a few first surgeons from the existing
proctors according to a manufacturer's recommendation.

(2) The first surgeons gain experience and become certified RG proctors for the new robot. (3) The RG proctors forthe new robot support surgeons at other institutions (second
surgeons) to start using it. Various new surgical robots haverecently been introduced [26, 27]. Developing guidelines
and recommendations led by each society was important
for the safe introduction and spread of new surgical robots.
While these regulations may assure the safe introduction of
new robots, they also deprive young surgeons of the opportunity to start robotic surgery, and it is desirable to evaluate
and improve whether the current safety attention is not toomuch.
This study had several limitations. This was a singleinstitution case series with a small sample size. Furthermore, almost all patients in this study had clinical stage
I/II diseases. They underwent distal gastrectomy, andpatients receiving preoperative chemotherapy were contraindicated for hinotori during the study period. Accumulation of clinical series with advanced diseases andfurther investigations are required to determine the safety
and feasibility of RG with hinotori from both surgical andoncological standpoints. In terms of indication of hinotori
or da Vinci for robotic gastrectomy, although this study
showed that hinotori could be safely applied in RG forSurgical Endoscopy

clinical stage I/II gastric cancer, da Vinci, which has amuch longer history and more clinical experiences, maybe
more widely applied in RG for gastric cancer at present.
However, as mentioned above, it is expected that hinotori
will be applied as widely as da Vinci to various patientswith gastric cancer as advanced energy device is developed and clinical experience accumulates. Also, this study
didn’t investigate the cost because it is a single-arm study
in the introductory phase. The high cost of robot-assisted
surgery is an important issue [5]. At present, the price ofthe hinotori system is lower than that of da Vinci (210
million vs. 270 million Japanese Yen), whereas runningcosts such as instruments and maintenance are considered
to be at least equivalent. The widespread use of hinotori
is expected to lead to price competition and a reduction in
the overall cost of robotic surgery.

Conclusions
This study found that robotic gastrectomy with standard
lymphadenectomy for gastric cancer using hinotori can besafely performed.
Supplementary Information The online version contains supplementary material available at https://d​ oi.o​ rg/1​ 0.1​ 007/s​ 00464-0​ 24-1​ 0695-0.
Acknowledgements We thank Maruzen Co., Ltd. (Tokyo, Japan) for
the English language editing. We are indebted to Sysmex Corporationand Medicaroid Corporation for their dedicated support in this project.
Author contributions All authors have fully satisfied the ICMJE
authorship criteria as detailed in the following: Study design: SI, MN,
IU and KS; Data collection: SI, MN, SS, YU, AS, KS, YW and TT;
Statistical analyses and interpretation: SI, MN, SS, YU, SA, KI and
KS; Drafting of the manuscript: SI, MN and KS; Critical revision of
the manuscript for important intellectual content: MN, IU and KS. All
authors have read and approved the final version of the manuscript andare accountable for all aspects of the work, particularly ensuring thatquestions related to the accuracy or integrity of any part of the work
are appropriately investigated and resolved.
Funding This work was not supported by any grants or funding.

Declarations
Disclosures SI, MN, SS, YU, KS, AS, SA, YW, TT, KI, IU, and KS
have no commercial associations or financial involvement that might beconstrued as a conflict of interest in connection with the submitted article. IU has received lecture fees from Intuitive Surgical, Inc., outsideof the submitted work. IU has been funded by Medicaroid, Inc. in relation to the Collaborative Laboratory for Research and Development inAdvanced Surgical Technology, Fujita Health University. KS has been
funded by Sysmex, Co. in relation to the Collaborative Laboratory for
Research and Development in Advanced Surgical Intelligence, Fujita
Health University, and has also received advisory fees from Medicaroid, Inc., outside of the submitted work.

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