Robotic technology and endoluminal surgery in digestive surgery

BACKGROUND. Colorectal cancer (CRC) is the third most common cancer in males and second in females, and the fourth most common cause of cancer death worldwide. The implementation of screening programs has allowed to the identification of an increasing number of early-stage neoplastic lesions. Presently, superficial colorectal neoplasms (including precancerous lesions and early cancer) can be resected in the colon by Endoscopic Mucosal Resection (EMR) and Endoscopic Submucosal Dissection (ESD), while in the rectum by Transanal Endoscopic Microsurgery (TEM). They are the preferred choices inside of the minimally invasive panorama regarding the CRC treatment. TEM technique offers more advantages than EMR and ESD, but it can’t overcome the recto-sigmoid junction. Many authors, research institutes and biomedical industries have proposed different solutions for microsurgery dissection of early lesions in the colon, but all these proposals have in common the development of platforms expressly designed for this use, with significant purchasing and management costs. The aim of our research project is to develop a robotic platform that allows to treat lesions throughout the colon limiting the costs of management and purchasing. This new robotic platform, developed in collaboration with Scuola Superiore Sant’Anna in Pisa, is called RED (Robot for Endoscopic Dissection). At the tip of a standard endoscope a hood (RED) is placed. RED is equipped by two extractable teleoperated robotic arms (i.e., diathermic hook and gripper); their motion is provided by onboard miniaturized commercial motors and a dedicated external platform. The endoscopist holds the endoscope near the lesion, while the operator drives the robotic arms through a remote control. MATERIALS AND METHODS. Several preliminary studies have been conducted in the following order. A first test was conducted for identification of force value for lifting and pulling maneuvers using a modified TEM instrument. A CAD study was conducted to determine the maximum size that the hood must have in order to overcome the critical angle represented by the splenic flexure. Several tests were conducted to determine the degrees of freedom of each robotic arm, starting with the CAD drawing to make subsequently the mock-ups of each configuration. Finally, a 3D mock-up was produced that was assembled on an endoscope to perform the in vitro test to evaluate the workspace and field of view using a pelvic trainer for TEM. RESULTS. The first test shown that the minimum force that the gripper will have to develop with the push-pull is 1.5N. The CAD study shown that the maximum dimensions the hood must have to overcome splenic flexure are: maximum diameter 28mm, maximum length 57mm. After several configurations was been tested, the final prototype features are: gripper arm with pitch sliding and open/close of the tip and diathermic hook arm with pitch, roll and sliding. There will be 6 such distributed motors: 3 external motors for the gripper arm that will operate through cables contained in a sheath adherent to colonscope and 3 embedded motors for diathermic hook arm (one integrated on the hood for the sliding degree of motion and the other two inside of the arm). The in-vitro test has been carried out to evaluate the workspace and they proved that the operating field vision is not obstructed by the hood and the working range is sufficiently wide to perform a dissection. CONCLUSION. Tests conducted up to this point have allowed us to identify the overall layout of the RED: dimensions, degrees of freedom, number and distribution of motors needed for the operation of robotic arms; moreover, it is proved that the device, once assembled, maintained the visual and operational field characteristics necessary to perform an accurate dissection. The next step will be to realize a RED steel final prototype and in-vivo tests will be carry out to replicate an endoscopic dissection into the colon.