Feature Story: Flexible transoral robotic surgery system

Among all head-neck cancers, Oropharyngeal cancer comprises about 85%. Today, there are about 0.7 million people worldwide who are diagnosed with this cancer in each year. Owing to industrialisation, the increased number of smokers and the aggravation of air pollution, the morbidity of this kind of cancer has seen a rising trend. Alarmingly, the 5-year survival rates have hovered around 50% for the past ten years. Surgery is the most effective treatment done to this kind of cancer. However, due to the location and the extremely narrow cavity of the oropharynx, as well as limitations of conventional rigid surgical instruments, surgeons have to open the throat to remove tumors or cancers. From this picture, it is obvious the open surgery will bring serious trauma to patients, which can lead to significant morbidity.

With the improvement in technology, especially the development of robotics, a less invasive approach is available. This approach is known as transoral robotic surgery. With the assistance of surgical robotic systems, surgeons can conduct treatments through the mouth. Compared with open surgeries, it can benefit patients with reduced morbidity. There is less trauma to muscles or other tissues and patients will not be left with a scar on the face or neck after treatment. The recovery time for patients has also been found to be significantly reduced.

Nowadays, some robotic systems have been developed and a number of transoral robotic surgeries have been completed with them. The most widely used one is the da Vinci surgical system. Its instruments have flexible wrists and can work as dexterously as human hands. Moreover, it can provide visual feedback to the surgeon and achieve high accuracy. The teleoperation can also remove the tremor of the surgeon’s hands. However, its disadvantages are also obvious. Firstly, the bulky and straight working arms make manoeuvring in small tight cavities challenging. The lack of haptic feedback will also bring difficulties to more delicate operations. Lastly, this system is costly in terms of both initial installation and continued maintenance, which leads to higher costs for patients.

To make up for these defects a new surgical robotic system that is applicable for transoral robotic surgery has been developed by Dr Ren Hongliang’s team of NUSRI.

As shown in Fig.1., the developed surgical robotic system contains two manipulators and one endoscope with LED illumination. Dexterous and flexible manipulators are the highlight of this design, which is comprised of a 3-DOF flexible parallel mechanism and a 2-DOF forceps. The flexible parallel mechanism utilizes super-elastic Ni-Ti rods and micro universal joints to achieve two bending motions and one linear motion. Compared with traditional parallel mechanisms, it has a more compact structure, enhanced dexterity and lower manufacturing cost. Additionally, the forceps are able to achieve 360° rotations and easily lift objects of 500 grams. As such, designed manipulators have adequate flexibility and grasping force in confined and complex working environments.

The flexible shaft is employed to transmit force in this surgical robotic system, which allows actuators to be separated from the main body of the robot contributing to the reduced size of the robot. Operators can use controllers to achieve tele-operation of this system. Two manipulators are capable of achieving multi-DOF dexterous manipulations.

Compared with current surgical robotic systems, this system developed by their research group has a reduced size, enhanced flexibility, and increased load capacity. In future, they will carry out a series of experiments, including cadaver experiments, animal experiments, and patient experiments to validate the feasibility and outcome of this surgical robotic system.