Kinematic and Workspace Comparison of Four and Five Degree of Freedom Miniature In Vivo Surgical Robot

The adoption of Laparo-Endoscopic Single-Site Surgery (LESS) provides potential for surgical procedures to be performed with the use of a single incision into the peritoneal cavity. Benefits of this technique include faster recovery times, decreased chance of infection, and improved cosmetic results as compared to traditional surgery. Current technology in this area relies on multiple laparoscopic tools which are inserted into the peritoneal cavity through a specialized port, resulting in poor visualization, limited dexterity, and unintuitive controls occur. To mitigate these problems, this research group is developing a multi-functional, two-armed miniature in vivo surgical robot with a remote user interface for use in LESS. While this platform’s feasibility has been demonstrated in multiple nonsurvival surgeries in porcine models, including four cholecystectomies, previous prototypes have been too large to be inserted through a single incision. Work is currently being performed to reduce the overall size of the robot while increasing dexterity. Using the knowledge gained from the development of a four degree of freedom (DOF) miniature in vivo surgical robot, another robot prototype was designed which was smaller, yet was able to utilize five DOF instead of four. The decreased size of the five DOF robot allows it to be completely inserted into the peritoneal cavity through a single incision for use in LESS. Each arm of the surgical robot is inserted independently before being mated together and attached to a central control rod. Once inserted, this platform allows for gross repositioning of the robot to provide surgical capabilities in all four quadrants of the abdominal cavity by rotating the control rod. The additional degree of freedom allows for reaching positions in the surgical workspace from varied angles. This paper will provide a comparison of the four DOF and five DOF miniature in vivo surgical robots. The implications of the added degree of freedom on the forward and inverse kinematics will be discussed and the workspace of each robot will be compared. Additionally, the increased complexity of the control system for the remote surgical interface in moving from four DOF to five DOF will be demonstrated. Finally, results from non-survival procedures using a porcine model will be presented for both robots. This comparison will provide useful information for further development of miniature in vivo surgical robots as the goals of decreased size and improved dexterity are approached. INTRODUCTION Performing surgery using long instruments while working through small incisions in the abdominal wall, such as in laparoscopy, offers recognized patient advantages including shortened recovery times, improved cosmetics, and reduced expense. While replacing a large open incision with three to five small incisions offers significant patient advantages, continuing work focuses on further reducing the invasiveness of surgical procedures. Laparo-Endoscopic Single-Site surgery (LESS) is a new alternative to laparoscopic procedures that completely eliminates all but one small external incision. Existing methods for performing LESS use multiple articulating, bent, or flexible laparoscopic instruments that are inserted into the abdominal cavity through a single specialized