Toward safe clinical deployment of remote robotic surgery in Japan: five-year validation of the hinotori™ system using 5G wireless communication

Abstract

Remote robotic-assisted surgery (RRAS), a form of telesurgery, offers a potential solution to Japan’s surgeon shortage and regional disparities in care. Despite advances in robotic systems and modern communication technologies, including both 5G wireless and wired networks, clinical adoption remains limited due to regulatory, infrastructural, and institutional barriers. This review consolidates five years (2020–2025) of technical and operational validation of the hinotori™ Surgical Robot System—a domestically developed platform—in alignment with the 2022 Japanese Remote Surgery Guidelines. Based on over 30 remote-session evaluations by Kobe University, Medicaroid, and NTT DOCOMO, we summarize system performance across key domains: communication latency, QoS-based prioritization, VPN redundancy, fail-safe mechanisms, electromagnetic compatibility, human–system interaction, and legal compliance. Under optimized Sub6 5G SA conditions, the system consistently achieved a round-trip latency of approximately 100 ms and stable stereoscopic video transmission, even during simulated 1 Gbps congestion. Safety was ensured through automatic standby, dual-cockpit fallback, and real-time monitoring. Although hinotori™ meets technical and safety criteria, full-scale implementation remains constrained by legal requirements—particularly the mandate for an on-site physician under Article 20 of the Medical Practitioners Act. Supervised telesurgery, where remote surgeons assist on-site teams, is legally permissible and may serve as a transitional model. This review integrates technical findings with policy considerations, proposing a path toward safe, equitable, and sustainable RRAS deployment in Japan. To our knowledge, this is the first comprehensive review aligning domestic telesurgical validation with national policy benchmarks, offering a foundation for future regulation, accreditation, and digital surgical integration.

Introduction

Remote robotic-assisted surgery (RRAS), a form of telesurgery, offers a promising solution to the shortage and uneven distribution of surgeons in Japan, particularly in underserved regions such as rural areas [1]. Despite increasing demand, robotic systems remain concentrated in metropolitan centers. A previous study reported that urban hospitals performed five times more robotic prostatectomies than their regional counterparts [2].

Telesurgery may reduce the disparities between urban and rural areas. However, it is limited by its dependence on ultra-reliable, low-latency communication infrastructure. Simulator and animal studies have shown that round-trip latency beyond approximately 100 ms impairs hand–eye coordination [3, 4]. Furthermore, jitter and packet loss degrade depth perception and compromise operative safety [5, 6]. Based on these findings, the 2022 Japanese Remote Surgery Guidelines (JSS-RSG) stipulated an end-to-end latency of ≤ 100 ms, secure closed-network architecture, and robust redundancy [7].

Globally, several countries have already demonstrated the feasibility of telesurgery under real-world clinical conditions. Europe has recently demonstrated clinical feasibility with the Bordeaux–Beijing partial nephrectomy in 2024, achieving 132 ms latency over 8264 km [8]. In 2025, the United States completed its first telesurgical procedure under formal FDA approval, performing a transcontinental operation between Florida and Angola [9]. China has rapidly implemented dozens of long-distance procedures since 2019, supported by its 5G infrastructure[10] and domestic robotic systems[11]. These cases highlight that clinical-grade telesurgery is achievable when supported by appropriate technical and regulatory frameworks.

Japan has achieved near-universal deployment of fiber-optic infrastructure, which offers high bandwidth, low latency, and strong resistance to electromagnetic interference [12]. These advantages make fiber the gold standard for reliable communication in fixed medical settings. However, high-performance connectivity is not always available at the surgical site, particularly in rural or mid-sized institutions where internal networks may vary. Wired infrastructure is also less suitable for mobile or emergency use. In this context, 5G networks and their wide coverage provide a complementary and flexible option for expanding telesurgical access beyond urban centers.

This review consolidates five years (2020–2025) of technical and operational validation of the hinotori™ Surgical Robot Systemin the context of the JSS-RSG that were conducted by Kobe University, Medicaroid, and NTT DOCOMO [9] (Fig. 1). Drawing from over 30 remote-session demonstrations, we summarize system performance in relation to national benchmarks and discuss practical considerations for future clinical deployment. This review highlights selected findings from validation studies, while detailed quantitative analyses are outside its scope and will be addressed in a separate publication.

Fig. 1.

Remote telesurgical validation using the hinotori™ surgical robot system. A Photograph from a demonstration experiment simulating remote telesurgical support. Although the master cockpit and the operation unit were located in the same operating room, the system was configured to emulate remote operation conditions. B Network configuration used in the validation experiment. 5G wireless access was combined with a wired backbone via multi-access edge computing (MEC) and secured using a virtual private network (VPN). This architecture simulated a round-trip communication distance of approximately 800 km. Over 30 sessions were conducted to evaluate latency, jitter tolerance, failover response, and communication stability

To our knowledge, this is the first comprehensive review that directly links long-term domestic validation of a commercially available telesurgical platform with Japan’s national regulatory standards. An evidence-based foundation is necessary for future policy, accreditation, and safe clinical rollout.

Communication and control infrastructure for safe telesurgery

Communication reliability is important for performing telesurgery. Network disruptions, such as latency, jitter, or packet loss, can impair visualization or instrument control during critical moments, directly compromising patient safety [4, 14]. Round-trip latency below 100 ms preserves hand–eye coordination during robotic telesurgery performed by experienced surgeons, whereas delays exceeding 150–200 ms significantly impair surgical precision [15, 16], especially in dual-cockpit settings [17]. To mitigate these risks, encrypted and redundant communication channels are recommended in both the guidelines and academic literature [18–20], including the 2022 JSS-RSG [7].

Bandwidth stability is essential for high-definition stereoscopic video and real-time telemetry [21–23]. Standalone (SA) 5G networks offer low-latency, high-throughput connections with network slicing capabilities that outperform non-SA (NSA) configurations [11, 24]. For example, a ~ 5000 km telesurgery trial in China using SA 5G achieved a median one-way latency of 73 ms and zero packet loss, enabling safe long-distance procedures [11].

To evaluate baseline performance in a realistic 5G environment, we tested Sub6-based SA 5G networks [25], which consistently achieved round-trip latency around 100 ms during continuous high-definition video transmission. In contrast, NR-DC configurations [26], which combine Sub6 and millimeter-wave bands, exhibited greater jitter and unstable frame delivery, making Sub6 more suitable for latency-sensitive telesurgical procedures.

To assess communication robustness under realistic mobile network conditions, we collaborated with NTT DOCOMO to simulate bandwidth congestion at a shared 5G base station. In telesurgery, it is important that surgical video and control signals are transmitted without delay, even when many other users are sharing the same network.

In NTT DOCOMO's 5G Wide service, base stations perform quality of service (QoS) control over a radio interface based on 5QI information [27, 28]. This ensures stable performance despite competing traffic. Without QoS control, packet loss and video degradation were observed with background traffic as low as 200 Mbps. On the other hand, with QoS enabled, stable transmission was maintained even under competing traffic exceeding 1 Gbps. These findings underscore the importance of packet prioritization for ensuring telesurgical safety on public networks.

Redundancy was evaluated by configuring two independent communication pathways(a primary and a backup line)and conducting failover testing to ensure uninterrupted telesurgical operation during simulated line failures. This configuration enabled automatic tunnel recovery and dynamic rerouting. Simulated failures, including SA-NSA handovers, showed VPN reconnection within 5–11 s, without the need to reboot the system. Other research groups have demonstrated that combining primary connections with multi-carrier failover mechanisms can further improve network robustness during communication failures [18–20].

In addition to network-level redundancy and prioritization, transport protocol selection also plays a critical role in maintaining low-latency surgical data exchange. Standard TCP/IP introduces latency through congestion control and retransmission mechanisms, which may be unsuitable for real-time surgical telemetry [29, 30]. Newer telesurgical systems are increasingly adopting UDP-based streaming protocols or real-time optimized protocols, such as QUIC, which offer faster transmission and reduced jitter in network environments prone to loss [31, 32].

In summary, when configured with Sub6-based 5G SA, QoS prioritization, and robust VPN redundancy, the hinotori™ Surgical Robot System fulfills essential communication standards for safe and continuous telesurgery.

Robotic system design for remote operation

While robust networks are essential, telesurgery also requires robotic platforms that can operate safely and responsively over distance. Most existing surgical robots, including da Vinci [33] and hinotori™ [34], were originally designed for on-site cockpit use. Adapting them for remote application necessitates reengineering software architectures to manage control signals and video feedback across wide-area networks without latency or desynchronization [35]. The JSS-RSG mandates that the master–slave configuration must support physical separation of the cockpit and patient unit [7]. However, progress has been slow due to regulatory caution and limited commercial incentive to redesign FDA-cleared robots [36].

Among the required elements, visual feedback is important because surgeons rely on stereoscopic 3D imagery to perceive depth, identify tissue planes, and perform precise movements [37]. Any degradation in this visual information, such as reduced frame rate, compression artifacts, or narrowed field of view, can impair detection of microbleeds or subtle anatomical landmarks [13, 38–40]. The JSS-RSG requires high-resolution stereoscopic video [7]. Multiple studies have reported that 3D imaging improves depth perception, enhances precision, and reduces physical and cognitive fatigue [38–40]. On the other hand, degraded or delayed imagery has been associated with increased error rates and mental strain [44, 45].

In addition to vision, hardware limitations significantly constrain remote autonomy because essential intraoperative functions, such as instrument exchange, lens cleaning, and suction, still require on-site staff. Thus, there is a lack of self-recovery capability in most current systems. Moreover, remote use amplifies the consequences of mechanical failures because the remote surgeon cannot physically intervene. Therefore, functionalities, such as real-time diagnostics, automatic fault detection, and actuator-level redundancy, are necessary [33]. Thus, the JSS-RSG recommends comprehensive preoperative system checks and mandates the presence of on-site technical support [14].

To validate these safety functions under real-world conditions, we conducted structured evaluations of the hinotori™ Surgical Robot System under simulated latency and jitter. Surgeons were able to complete operative tasks even at elevated delay levels, although fine motor accuracy declined as latency increased. These results are consistent with previously reported latency thresholds for safe telesurgical performance [4, 15, 16].

To validate these safety functions under real-world conditions, we conducted structured evaluations of the hinotori™ Surgical Robot System using simulated latency and jitter. Even with delays up to 180 ms, surgeons were able to complete operative tasks without unintended movement or control failure, although fine motor accuracy began to decline beyond 120 ms, which is consistent with latency findings described in Sect. 2 and prior literature [4, 15, 16]. To assess fault recovery and fail-safe mechanisms, we simulated sudden disconnections at both the router and 5G device levels. The hinotori™ robot reliably entered a safe standby mode, halting all instrument motion without erratic behavior, and in most cases, VPN reconnection restored full control without requiring a system reboot.

These recovery mechanisms mirror fault-tolerant designs seen in teleoperation systems used in hazardous environments [46]. Thus, the hinotori™ system fulfills essential safety and resilience criteria. Based on these validations, the hinotori™ robot satisfies core technical requirements for remote telesurgical use, including reliable master–slave separation, high-fidelity stereoscopic vision, automatic fail-safe behavior, and autonomous reconnection following disconnection. Broader clinical deployment will benefit from continued system improvements, particularly in reducing reliance on local staff, incorporating mechanical redundancy, and enabling multi-cockpit operability to support remote mentoring and distributed surgical collaboration.

Security and safety

Telesurgery aims to integrate cyberspace with the operating room.　Data security is an important consideration, as any breach or system failure during a procedure could have immediate consequences for patient safety [47, 48]. All transmitted data, including surgical video, robotic control signals, and patient information, must be protected from interception or tampering. The 2022 Japanese telesurgery guidelines mandate the use of VPNs with robust encryption to ensure secure communications [7].

5G Standalone (SA) networks adopt a secure-by-design architecture standardized by 3GPP, including mutual authentication between devices and the core network, SIM-based identity protection, and strong 128-bit encryption for both control- and user-plane traffic [28]. These features offer substantial improvements over legacy wireless networks in terms of confidentiality and protection against impersonation.

However, despite these safeguards, 5G's use of an open wireless medium introduces additional vulnerabilities not typically seen in wired fiber networks. Telesurgery systems may be exposed to radio frequency interference, jamming, or rogue base stations that spoof legitimate signals. Such attacks could degrade connectivity, compromise data integrity, or cause service disruptions. Furthermore, the air interface remains susceptible to denial-of-service (DoS) attacks or protocol-layer exploits that can increase latency or interrupt surgical procedures [49, 50].

To meet these safety demands, we adopted a closed network architecture for all validation trials, utilizing a server-based VPN with multi-access edge computing for direct connectivity, thereby isolating all surgical data, including video, control commands, audio, and telemetry, from the public internet. Dual-layer encryption using IP-VPN and IPsec protocols was applied without introducing perceptible latency, and the configuration complied with Japanese medical data protection standards [51].

We simulated sudden network disconnections to test the system’s resilience using a programmable emulator. In each case, the hinotori™ robot entered a predefined safe standby mode, halting all instrument motion immediately and without unintended activity. This confirmed that the software’s fail-safe logic functioned correctly under transient fault conditions. In most scenarios, VPN reconnection restored full control without requiring system reboot, and in dual-cockpit configurations, local operators could assume control seamlessly, enabling uninterrupted surgical continuity.

Electromagnetic interference (EMI) tests were conducted in line with IEC 60601-1-2 [52]. The hinotori™ system was exposed to simulated emissions resembling those from electrosurgical units and radiologic systems. No signal degradation or operational anomalies were observed, except for transient and reversible abnormalities in the video transmission equipment. Our findings are supported by a 2002 survey on EMI by the Ministry of Internal Affairs and Communications [53] that reported no interference across 4G and 5G SA frequency bands. Thus, this suggests hospital infrastructure compatibility.

Real-time system monitoring was implemented using Zabbix [54] to oversee VPN routers, switches, and encoder/decoder systems. Although internal robotic subsystems were not directly monitored due to segmentation, the setup enabled early detection of packet loss spikes or frame delays, allowing timely interventions to prevent disruption. On-site human redundancy, consisting of licensed medical and technical staff that could intervene in the event of system failure, was also maintained throughout all sessions in accordance with Article 20 of the Medical Practitioners Act [55] and JSS-RSG requirements [7]. Simulated blackouts confirmed that control could be transferred safely to the local team, and the robot resumed normal operation once the VPN connection was restored.

In summary, secure architecture, fail-safe logic, EMI resilience, active monitoring, and human redundancy function as an integrated safety system. Fail-safe logic and automatic standby mechanisms provide a passive safeguard against critical faults [56, 57], and real-time monitoring systems actively detect anomalies before they escalate [33]. On-site human redundancy and dual-cockpit configurations further ensure procedural continuity during unexpected disruptions.

Human–system interaction

Telesurgery introduces unique challenges in human-system interaction due to the physical separation of the surgeon, patient, and support staff, which disrupts real-time task coordination, physical gesture-based communication, and shared situational awareness. As a result, reliance on visual and audio channels is necessary, and the importance of stereoscopic 3D imaging is further magnified in remote contexts where surgeons must rely solely on visual input without tactile feedback [37, 41–43]. Any degradation in video quality, such as jitter, latency, or compression artifacts, increases cognitive load [58]. Cognitive ergonomics are important in cockpit interface design and systems that maintain consistent visual feedback are necessary.

Communication with on-site staff is important for patient safety. Unlike traditional surgeries where ambient cues and physical presence aid coordination, telesurgery depends on mediated audio-visual links. Delays or distortion in this channel can impair response timing and shared situational awareness [4, 14]. To address these challenges, telesurgical systems should incorporate low-latency, high-reliability communication tools, as well as standardized protocols for task delegation and emergency handling [59–61]. In addition, support features, such as telestration, OR overview cameras, and shared vital sign displays, are needed to compensate for the lack of physical interaction and reinforce understanding among the medical staff [62–64].

The hinotori™ system integrates dual-cockpit functionality and structured communication workflows. In validation studies, novice surgeons performed more safely and efficiently when mentored remotely by experts. This highlights the importance of human–human collaboration in remote settings [36, 49]. Moreover, existing robotic surgery training often overlooks the effects of network instability. In our simulation-based curriculum, we introduced challenging conditions such as latency, jitter, and blackout. Surgeons adopted adaptive strategies, including deliberate pauses and slower hand speed, to preserve accuracy under degraded feedback [65, 66].

In summary, successful telesurgery is determined by communication infrastructure as well as optimization of human-system integration, including intuitive interface design, real-time collaboration support, and training under realistic network conditions, particularly for novice users and multidisciplinary teams.

Regulatory and societal challenges

The clinical implementation of telesurgery in Japan is constrained by legal, financial, and institutional limitations, including the prohibition of remote-only surgery under Article 20 of the Medical Practitioners Act [55], unreimbursed infrastructure costs, and the lack of standardized accreditation systems. Current legal interpretations mandate direct physician–patient interaction prior to surgery, effectively prohibiting fully remote telesurgery unless a licensed surgeon is physically present on-site. This view was reaffirmed in the 2022 statement by the Japan Surgical Society, which emphasized the need for legislative reform to permit independent remote surgery [7]. Financial barriers further limit adoption. Although robotic-assisted surgeries are reimbursed under the national health insurance scheme, this framework does not account for remote surgical participation, meaning that hospitals must independently fund high-speed networks, IT redundancy, and personnel training without financial support. Consequently, even hospitals in underserved regions have little incentive to invest in telesurgical infrastructure.

Data security and institutional liability also pose significant barriers. While encryption and VPNs are technical solutions, national guidelines stress the need for formal legal agreements between institutions to define accountability and prevent disputes in case of adverse events [7, 67]. Yet such agreements remain rare due to legal ambiguity. Furthermore, participation in telesurgical trials is limited to accredited institutions with existing robotic programs and experienced operators; however, Japan currently lacks a unified national framework for certifying telesurgical centers, platforms, and operators. This regulatory gap complicates quality assurance and hinders equitable expansion [7].

Geographic disparities highlight the importance of public support. A few government-funded pilot programs have helped rural hospitals upgrade communication infrastructure; however, there is still no national policy to subsidize ongoing costs such as 5G data usage, equipment maintenance, or staff education. In contrast, other countries, including China [68, 69] and Kuwait [19], have adopted more flexible legal frameworks and introduced reimbursement schemes and public funding to actively promote telesurgery, encouraging both clinical uptake and private sector investment.

To enable sustainable and equitable deployment of telesurgery in Japan, a coordinated strategy is essential. Priority actions include revising outdated statutes, establishing reimbursement mechanisms for remote participation, codifying liability protocols, and implementing a transparent certification and accreditation system. Drawing from successful international precedents, Japan is well-positioned to create a policy framework that safeguards patient safety, encourages technological innovation, and ensures regional equity in surgical care.

Toward clinical implementation

The next critical phase for implementing RRAS in Japan is a structured transition from technical validation to clinical deployment. The successful implementation of such systems requires technical readiness in addition to supportive regulatory, institutional, and social infrastructure. Engineering validation studies suggest that the hinotori™ Surgical Robot System, when operated under optimized Sub6 5G SA conditions with approximately 100 ms latency, jitter-tolerant buffering, and robust fail-safe mechanisms can safely support telesurgical procedures under real-world network conditions. Initial clinical deployment should begin with investigator-led studies at accredited institutions to confirm surgical safety, system usability, and communication reliability under realistic network conditions.

As discussed previously, legal reform remains a prerequisite for further implementation. Under the current interpretation of Article 20 of the Medical Practitioners Act [53], telesurgery without direct physician–patient contact is not permitted.

We propose that the near-term objective should focus on supervised remote surgery models, specifically, those in which an on-site licensed surgeon performs the procedure while receiving real-time guidance or support from a remote expert. This approach is already recognized under current Japanese regulations, including the 2022 guidelines issued by the Japan Surgical Society [7], which classify models, such as telementoring or telesurgical support, as being legally compliant (Fig. 2). Domestic validation studies are currently exploring the feasibility of telesurgical support models in which expert surgeons provide remote procedural guidance. Preliminary findings suggest that such systems may enable safe and effective support without compromising surgical quality [70, 71]. Remote guidance enables junior surgeons in underserved areas to receive real-time mentorship from experienced specialists, thereby improving local surgical capacity while maintaining patient safety standards. Supervised remote surgery, thus offering a legally compliant and scalable model that can serve as a foundation for future full telesurgical implementation.

Fig. 2.

Conceptual models of remote robotic-assisted surgery under current Japanese regulatory conditions. An illustration comparing three models: (top) Telementoring, in which a remote expert provides non-invasive visual guidance to an on-site surgeon; (middle) Telesurgical Support, where both remote and local surgeons control surgical cockpits collaboratively; and (bottom) Fully Remote Surgery, in which the remote surgeon performs the entire procedure without on-site medical staff. Under current Japanese medical law (Article 20 of the Medical Practitioners Act), only telementoring and telesurgical support are legally permissible, whereas fully remote surgery remains restricted

The development of a formal certification system is important. RRAS requires distinct competencies, including latency adaptation, visual compensation, and remote team coordination. Simulation-based training and structured credentialing should be introduced, as well as a national registry for safety monitoring and quality assurance.

In the long term, RRAS could become part of a broader digital surgical ecosystem that integrates telepathology, cloud-based imaging, and remote education. Japan’s robust telecom infrastructure and centralized healthcare policy provide a strong foundation for this transition. Widespread adoption will depend on institutional trust, legal clarity, and sustained public investment. Future policy must prioritize safety, accessibility, and equity as well as technological advancement.

Author contributions

Takuto Hara: conceptualization, formal analysis, investigation, methodology, writing – original draft, review, and editing. Yoshifumi Morihiro: formal analysis, methodology, writing – original draft, review, and editing. Yuki Horise: formal analysis, methodology, writing – original draft, review, and editing. Shuhei Komatsu: formal analysis, methodology, writing – original draft, review, and editing. Masunao Ohashi: formal analysis, methodology, writing – original draft, review, and editing. Hiroaki Kitatsuji: ormal analysis, methodology, writing – original draft, review, and editing. Akihisa Yao: review and editing. Yoshihiro Muragaki: review and editing. Hideaki Miyake: review, editing, and supervision.

Funding

Open Access funding provided by Kobe University.

Cabinet Office Research Grant

Recipient Project of the Government Grant for the Establishment of Regional Universities and Industries for FY2020

Urban Innovation Kobe grant

NTT DOCOMO, INC

Medicaroid Corporation.

Declarations

Conflict of interest

Hideaki Miyake received a research grant from Sysmex Corporation, unrelated to the present study. Yoshifumi Morihiro, Yuki Horise, and Shuhei Komatsu are employees of NTT DOCOMO, INC. Masunao Ohashi and Hiroaki Kitatsuji are employees of Medicaroid Corporation.

Approval of the research protocol by an Institutional Review Board

N/A.

Informed consent

N/A.

Registry and the registration no. of the study/trial

N/A.

Animal studies

N/A.