Flying High in Achieving a Medical Revolution: The hinotori Robotic-Assisted Surgery System

On any given day, modern hospitals have robots working in many ways, such as delivery robots carrying pharmaceuticals and samples, wearable robots helping with rehabilitation, and assistive robots help to feed people. While the mission of most robots is to provide the labor done by people, the hinotori was developed not to replace humans but to provide support. 

The surgical support robot allows teleoperation by a surgeon who observes camera images to manipulate robotic arms equipped with an endoscope or forceps. The concept of remote surgery emerged in the early 1970s and was originally devised by NASA to treat astronauts in space.^*2

In the late 1980s, surgeons used monitor screens and other devices to initiate laparoscopic surgery to treat the affected areas. Because it is not open surgery and only involves the insertion of cylindrical surgical instruments through multiple incisions (ports) in a patient’s body, this now popular procedure is minimally invasive and reduces the physical impact on patients. However, the movement of conventional laparoscope forceps was linear and lacked flexibility, and only two-dimensional images with limited viewing angles were available.^*3

On the other hand, the surgical support robot with its multi-joint arms offers a high degree of freedom of movement, provides three-dimensional (3D) images, facilitates the sense of depth, and allows the surgeon to operate the movable arms and hands with vision close to those of humans. Currently, the da Vinci Surgical System, manufactured by Intuitive Surgical, Inc., of the United States, dominates the surgical robot market. The system was released in 1999 and approved by the US Food and Drug Administration (FDA) in 2000. Since then, about 5,500 units have been in operation worldwide and now carry out more than 1.2 million procedures a year.^*4

The hinotori by Medicaroid, which was formed as a joint venture by Kawasaki and Sysmex Corporation, endeavors to enter the market monopolized by the mighty da Vinci. The partnership between Kawasaki, a leader in the world of industrial robots, and Sysmex, with its abundant expertise and networks in the field of advanced medicine, released the first made-in-Japan robotic-assisted surgery system in 2020. 

The new system was named after the masterpiece manga series, Hi no Tori (Phoenix), created by Osamu Tezuka. The name represents the will to support medical professionals who constantly deal in matters of life and death, just as Osamu Tezuka illustrated the value of life along with the phoenix.

Kawasaki’s specialties are in the art of producing robots with excellent maneuverability as exemplified by arms capable of fine operation (manipulators) and its sophisticated sensors. Since the introduction of the first industrial robot in Japan in 1969, the company has always been a leader for more than 50 years. Kawasaki has also handled many robots for semiconductor manufacturing and pharmaceutical processes that must be absolutely clean, which guarantees a solid background.

Thus, the hinotori development started in 2015. The elite engineers who had created Kawasaki’s robots worked on this long-awaited project, and it did not take long until the robot reached the level of dexterity to peel a grape. However, they were perplexed by comments from surgeons in the actual fields of medicine. Raizo Yamaguchi, vice director of the International Clinical Cancer Research Center (ICCRC) of Kobe University Hospital, who is a urologist with extensive expertise in robotic-assisted surgeries, recalls, “What was challenging was getting the engineers to understand what surgeons felt and experienced during surgery.”

Yamaguchi related a parable of a helicopter and a sports car to explain what was expected of a surgical support robot. “If an industrial robot fails, we can simply deactivate it, but can we do the same with a helicopter in flight? When faced with problems, a pilot must be able to maintain control of the aircraft as long as possible. The same goes for the robotic-assisted surgery system.” He continues, “Engineers tend to be conservative, thinking it’s dangerous if a knife is too sharp, but surgeons are confident in their ability to control sharp knives. We want a robot to be like a luxurious, high-performance, highly responsive sports car, but with redundant safeguards that permit the driver to use as many driving techniques as possible.” This parable specifically identified the technological challenges to be resolved by the engineers.

Three major components comprise the hinotori: (1) the operation unit positioned beside the patient and consisting of a cart and four arms with endoscope, forceps, or various instruments; (2) the surgeon’s cockpit, where the surgeon is seated to operate at a short distance; and (3) the vision unit to provide high-definition 3D images.

Tsuyoshi Tojo, the senior staff officer from Kawasaki who led the development project, finally determined three key concepts in the development of the hinotori: compactness, high-level safety, and maximum maneuverability. The size was reduced to fit the relatively small operating rooms in Japan, and the robotic arms were designed to match the width of the human arm, which had the favorable effect of not overwhelming the patient. However, this compactness was a hurdle to the development project.

Although it is a robot, the hinotori never moves autonomously. The system’s four arms and the instruments at the tips of the arms are tools that act as the surgeon’s eyes and hands to see, explore, grasp, cut, and suture. Each arm provides an eight-axis configuration, which means the degrees of freedom are greater than ordinary industrial robots with six and the human arm with seven. On top, the four-axis motion control of each instrument is added for a total of twelve axes that can achieve smooth, flexible motion.

Meanwhile, when the four compact arms can move freely, the risk of interference increases. A collision of the arms followed by a system stop during surgery may have serious consequences. Therefore, elaborate control of the arms was considered a crucial requirement.

Hirofumi Yamamori, who was in charge of developing the controls, comments, “Because each arm has to reach the target area through an incision that cannot be relocated, the arms must have a large operating range. Even when attempting to move an arm straight forward, the control process is still very complex because of the positions of the other arms and the angles of the joints.” The most favorable movement of an arm is not always the best option for the four as a whole. While visiting operating rooms to observe how surgeons move their arms and hands, and receiving their feedback, the developers repeated the trial-and-error process in steps to formulate a control method that would achieve the smooth operation of each arm without colliding with one another. They also conducted computerized simulations totaling 18 trillion sessions to identify the optimal control algorithms.

Size reduction also posed challenges to the mechanical design. The senior staff officer at Kawasaki, Wataru Doi, recalls, “If we make the arm thin to keep the device compact, the arm’s instrument becomes unsteady. If we try to use a long, thin part to make the operating range greater, the thinness means the arm cannot support its own weight. It took repeated efforts to find the optimal balance between the mechanical aspects of the system and software controls.” What served to resolve the problem was the combination of a high-output motor and a new reduction gear developed by Kawasaki together with a parts manufacturer. Tojo mentions the outcome, “The compact design optimizes the lines of movement around the operating table and provides ample space for the surgeon’s hands. We were able to generate advantages that benefit not only the surgeons but also the entire operating team.”

The surgeon cockpit has hand controls with finger operation, which is equivalent to a vehicle steering wheel and an aircraft yoke, and is the very component directly related to the capability to manipulate the system at will. Surgeons requested that the hand controls give the tactile sensation of being as light as air. It was a challenge, and Doi did not know how to fulfill such a request from an engineering perspective.

The key to resolving this issue was the gear reduction ratio. Because the hand control transmits a sense of heaviness when the friction increases between the motor and the reduction gear, the developers lowered the gear reduction ratio to decrease the friction. They added software sensory compensation to establish the best feel through integration of both the mechanical design and software control.

A dual monitoring system was employed for the other concept of development, for reasons of safety. The robot remains deactivated unless the sensor in the 3D viewer detects the surgeon’s gaze. In addition, an alarm is activated if the arms interfere with each other. However, according to Yamamori, the system allows a skillful surgeon to continue the procedure by careful manipulation even if the arms are about to collide or if an arm reaches the limit of its operating range.

On December 14, 2020, a press conference was held at ICCRC on the success of the initial surgery using the first domestically produced robotic-assisted surgery system, the hinotori. Dr. Masato Fujisawa, dean of the Kobe University Graduate School of Medicine (present-day president of Kobe University), who had been an advisor in the development of the hinotori system, operated the system for a total prostatectomy.

Subsequent to the more than four hours of surgery, Dr. Fujisawa commented to the press, “I’d score the manipulation perfect,” and said that he was extremely moved by the fact that they had achieved societal implementation of a new medical device.

The system also enjoyed success at a second facility, Wakayama Medical University, and a third, Tokushima University Hospital as well in April 2021. Where in the world is the hinotori going to fly for more records of accomplishment? Tojo foresees future possibilities, “We still have many issues to resolve, including virtual pre-operation simulations incorporating CT-scan images, the automation of simple suturing, and the inheritance of experienced surgical skills.”

Regarding the prospective evolution of surgical robots, Yamaguchi of the ICCRC reports that three navigational features will be subject to critical improvements: “One will be to enhance the level of procedural precision using accurately visualized images of the surgical field obtained by injecting fluorescent dye. Another will be to accumulate and analyze data from robotic surgeries performed by expert surgeons so that their expertise can be leveraged as best-practice examples. Finally, the advancement of telesurgery using 5G and 6G (5th- and 6th-generation) communication systems is also vital.” Some parties now positively encourage verification tests for real-time transmission of 8K images with the 5G communication system. Once the next-generation high-speed communication networks are popularized more broadly, telesurgery would be possible between remote locations without a time lag.

As the first step in proving this idea, on April 16, 2021, Medicaroid announced the initiation of the first demonstration experiment in the world to remotely control the made-in-Japan robotic-assisted surgery system via commercial 5G networks. The idea is that high-definition 3D surgical images and robot control signals are transmitted in real-time by means of NTT Docomo’s commercial 5G and cloud services, and the first target is to realize telesurgery support through this system, in other words, the doctor on-site uses the surgical support robot to carry out a procedure with the assistance of a skillful surgeon in the robot cockpit from a remote location.

The 5G technology and the hinotori system intend to create a society where everyone can receive equal quality healthcare services. Widespread, societal implementation of surgical support robots will bring advanced surgical practices to towns without specialists and borderlands isolated by the ocean. If trips to the Moon are common in the future, a travel agency brochure might contain an exciting copy: Take it easy! Doctors on Earth will take care of you if you get sick on the Moon.