Although uniportal VATS has a history spanning over more than a decade, it is only in the past few years that more complex procedures and a strong desire by uniportal surgeons to further minimize surgical access trauma have spurred on rapid advances in VATS equipment. The potentially improved cosmesis together with patient demand have seen uniportal VATS quickly spread across the world (1). It can be extremely important in uniportal VATS, perhaps more than in other approaches, to use appropriate instruments with technology more suited to coping with the challenges of operating through a single small incision. The most obvious problems to overcome during uniportal VATS are instrument fencing, limited range and angle of vision through the thoracoscopy as well as the difficulty in executing the task with the instruments themselves. The current perspective will focus on certain areas of technological innovation, namely endoscopes and insertable operating platforms, that can help overcome the aforementioned challenges both in the present and in the near future.
Advances in thoracoscopy
In VATS, as in other endoscopic surgery, the quality of vision offered by the endoscope is of paramount importance. Most commonly used thoracoscopes have the classical rigid rod lens design with a beveled tip which defines the viewing angle. To modify the field of view (FOV), one has to steer the endoscope shaft or use an endoscope with a different viewing angle. These maneuvers can increase the chance of fencing between the endoscope and surgical instruments, which may prolong the surgical procedure while offering limited viewing angles. These challenges are more profound during uniportal VATS where all the instruments pass through one small incision in approximately the same direction. An endoscope with a distal flexible tip could reduce the chance of fencing between instrument and endoscope since the FOV could be modified by simply bending the tip section only without movement to the main body of the thoracoscopy (2). The EndoEye by Olympus (3) and the Cardioscope developed by Li et al. (4) are some examples. In the EndoEye, the distal flexible tip section, much like that of a flexible bronchoscope, can be angulated to over 100° with a variable lens angle adjuster, enabling the endoscope a wide FOV. However, the surgical site is often crowded and although the desired viewing angle may be achieved with the adjustable bending tip of the Endoeye, the tip itself can take up more room than a straight scope and cause obstruction to other surgical instruments. Therefore, the Cardioscope has been designed to further reduce collision of instruments and to improve visualization around tissue structures by not only having a flexible distal tip section but also an adjustable length to this flexible section, providing an even wider FOV (4). Figure 1 shows the Cardioscope prototype being tested ex vivo and in vivo. Compared to the EndoEye, image quality of the current version of the Cardioscope is inferior. Further development is required to bring the Cardioscope to the operating theater.
One limitation of the conventional endoscopes is that the scope shaft occupies space within the uniportal surgical incision and interferes with other surgical instruments despite strategies to limit this (5). One approach to improve this is to develop a remote wireless steerable endoscope (WSE). At the start of the operation, the WSE is inserted into the thoracic cavity through the uniportal incision and magnetically anchored to the internal thoracic wall. The WSE transmits the video images of the surgical site to the monitor and the FOV is controlled by steering the WSE wirelessly. Thus, the WSE replaces the conventional thoracoscopy, with the main advantages of omitting the cables associated with endoscopes and not interfering with instruments at the surgical incision (6). Figure 2 shows the WSE prototype. In this system, the wireless camera is hanging on a wooden plank, of which the thickness is equivalent to the average thickness of the chest wall. The prototype demonstrated good performance in sliding, rotating and providing multiple viewing directions and angles (Figure 2). Without occupancy by the thoracoscopy, the uniportal incision can potentially be smaller. In addition, since the WSE would be away from the operating tools, this would avoid fencing, leaving more space within the pleural cavity for use of other surgical instruments. This type of endoscope is not commercially available yet, however it is under development and currently being tested by the authors at their institute.
Natural orifice transluminal endoscopic surgery (NOTES) platform
Uniportal VATS has contributed to the growing interest in developing other forms of single access instrument platforms, such as NOTES (or embryonic-NOTES) and single incision robotic surgery, which may well have significant roles in the thoracic surgery of the future (6). In 2013, Zhu et al. reported their initial experience of e-NOTES transumbilical thoracic sympathectomy in patients suffering from palmar hyperhidrosis using a 5 mm ultrathin flexible gastroscopy. The procedure involved incision of the diaphragm to reach the operating site in the chest cavity and subsequent ablation of the sympathetic nerve. Such an approach may be adequate for performing very simple procedures, however a more sophisticated endoscopic platform is needed for more complex thoracic surgery.
Equipment used for NOTES can be categorized into two groups: flexible equipment and miniaturized devices (7,8). These devices, some of which are merely prototypes for NOTES, have their own advantages and disadvantages, which are summarized in Table 1. Flexible instruments have a bendable shaft and can conform to a natural orifice or lumen. These instruments currently dominate in the application of NOTES. The better known examples include the Cobra produced by USGI (9), Anubiscope by Karl Storz (10), the EndoSamurai by Olympus (11), the MASTER system from EndoMaster (12) and the Flex System from Medrobotics (13). Since the shafts of these instruments are flexible, positioning of the surgical arms may be less accurate and in general the system is less stable. Therefore, a recent improvement in the equipment has been the development of adjustable stiffness due to shape lock, which provides more stability. It is also desirable to have different effector operating arms and instruments that can be easily exchanged via instrument channels within the scope system, rather than having to retrieve the scope from the patient to change the effector or worse still having fixed effector arms limiting the range of surgical instruments available to the surgeon. Another disadvantage of instrumentation in the current flexible platform set up is the limited triangulation between the scope and instrument arms due to the scope design and space confinement. Miniature devices, such as the Endoluminal Robotic Platform (14) by SSSA do not suffer from this problem (Table 1). The miniature robots are inserted into the body sequentially and are anchored and assembled at the surgical site. Compared with the flexible equipment, the miniature robots save space and avoid tool collision. However, the payload ability of these miniature robots is small and the implementation is very challenging. A hybrid approach would be recommended whereby the miniature robots provide imaging and assistance, while the main operation is performed by flexible instruments.
Robotic uniportal VATS
In contrast to the NOTES equipment, which usually has a flexible shaft, the instruments for uniportal robotic surgery mostly have a rigid shaft with a distal flexible section as the surgical arms (Figure 3). Examples of such systems include the da Vinci single site robot by Intuitive Surgical Inc. (15), the SPORT surgical system by Titan Medical Inc. (16), the SPIDER surgical system by TransEnterix (17) and the SJTU unfoldable robotic system (SURS) (18). The flexible surgical arms are positioned by the rigid shaft, which provides a stable platform, and its movement is controlled by wires, cables or ‘tendons’. The instrument triangulation and dexterity of these systems are much improved and superior compared to the previous NOTES equipment as the distal flexible section usually contains multiple bending segments. However, this makes the actuation unit much more complex and system reliability can be problematic. Meanwhile, the payload ability of these systems or the force the instrument arms can exert for surgical tasks remains limited. The development of novel flexible mechanisms could help to simplify the robot system while preserving the advantages of reachable workspace and dexterity of the surgical arm inside the body cavity (19,20). Also, stiffness control (20) of the flexible surgical arms could help to increase the payload ability as well as adapt the surgical arm to various tasks.
For both NOTES and single port access surgery, cauterization is frequently used for tissue cutting. This not only lightens the payload requirement of the surgical arms but is also one of the main methods of achieving hemostasis. However, the smoke cloud generated within the confined surgical environment often affects thoracoscopic image quality and operative progress. Therefore, smoke evacuation should be considered in developing such systems. Another common problem is the sterilization of the surgical arms and cameras in these robotic systems. Each surgical arm contains numerous movable complex components which can make proper sterilization difficult, costly and time-consuming. Conventional sterilization by autoclave could impair the mechanical strength of the wires and damage the electronic component. A further challenge relates to instrument replacement, which is inevitable in surgery. In these robotic systems, the flexible surgical arm, as mentioned above, is steered by numerous motors and cables. Since the actuation unit is integrated into the surgical arm, the sterilization becomes more difficult and the cost of replacement of each arm is much higher.
Endoscopes with ultra-high maneuverability, such as the Endoeye and Cardioscope, can potentially provide better vision of the operating field for the surgeon, while minimizing interference with other instruments co-sharing the single incision. WSE systems may be the ultimate solution for fencing between endoscope and instruments and can further decrease the size of the uniportal wound. Furthermore, the insertion of several endoscopes within the pleural cavity would allow an unprecedented panoramic view of the whole operating space. NOTES and single incision robotic platforms will become the next generation of tools for performing uniportal VATS, allowing the endoscope and ‘hands of the surgeon’ to be inserted into the chest cavity through an even smaller incision and enable operations with greater precision. Technology is evolving rapidly at a pace that we have never seen in the past. The present article only touches on certain aspects of endoscope development and insertable surgical platforms. The future development, refinement and success of uniportal VATS will to a large extent depend on advancing technology that will allow ever more complex procedures to be done through smaller incisions and with greater patient safety and satisfaction.
Funding: This work is supported by the Shun Hing Institute of Advanced Engineering (SHIAE), the Chinese University of Hong Kong, with project No. 8115049, and the Innovative Technology Fund (ITF), Hong Kong, with Project No. ITS/019/15.
Conflicts of Interest: The authors have no conflicts of interest to declare.
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