Synthesis and Workspace Study of Endoscopic Extenders With Flexible Stem

Endoscopic surgery is a less invasive method of surgery as compared to open surgery. However, indirect vision, limited hand movement and lack of haptic sensation, combined with the tiring posture of holding long tools makes it a very difficult task for the surgeon to perform (Tendick, 93; Faraz, June, 95). Consequently, the surgeon has a fraction of the dexterity and sensing of that of open surgery. This is specially the case in laparoscopic surgery which is a specific branch of endoscopic surgery, and is performed on the abdomen. The dexterity problem associated with laparoscopic surgery arises from the fact that the present rigid stem extenders can approach the surgical site with some fix orientation (determined by the connecting line between the position of surgical site and the port of entry). Lack of 2 DOF at the stem, to orient the tool’s tip to the desired orientation near the surgical site, prevents the surgeon from having the required dexterity and agility. By adding revolute/spherical joints on the stem, the required internal capability in orienting the tool can be achieved, and hence provide more dexterity for the surgeon. Although, there has been some publication in the literature about different design possibilities (e.g., Rinninsland, 93; Melzer, 93; Neisius, 94), as well as U.S. patents (Matsumaru, 92; Heimberger, 94), they are all dealing with special designs with specific design focus. There is a lack of general study of flexible endoscopic extenders with wider design objectives. For example, such objectives can be: (a) general type synthesis of the joint design, (b) formulation of workspace requirements of laparoscopic extenders, and (c) comparative study of different designs in search of the optimal design(s). The objective of this report is to have a systematic synthesis of the joints, as well as formulate the dexterous workspace for laparoscopic extenders with flexible stem, in order to find the optimum design.