Towards developing a robot assistant for uterus positioning during hysterectomy: system design and experiments

Background: In traditional laparoscopic hysterectomy, an assistant is typically assigned to hold a uterus manipulator to facilitate the surgical procedures. The responsibility of the assistant is to position the uterus according to the primary surgeon’s instructions. Throughout the surgery, which typically lasts more than 90 min, the assistant has to support the uterus manipulator with his/her hands, which easily causes fatigue to the assistant and eventually affects the manipulation performance and threatens the patient. Moreover, the manipulation done by the assistant may not always be satisfactory from the primary surgeon’s point of view. Thus, having a robot assistant which can release the human assistant’s hands from the manipulation task and allow the primary surgeon to directly position the patient’s uterus can be a solution. Methods: A four degrees of freedom (DOF) robot assistant is designed for positioning the patient’s uterus during hysterectomy. The robot assistant is composed of three parts, a 3-DOF robotic positioning arm, a 1-DOF motorized uterus manipulator, and a supporting stand of the robot. To improve safety, the remote center of motion (RCM) mechanism is applied to the design of the robotic positioning arm. The positioning arm generates a partial spherical workspace and allows the manipulation of uterus to be done in a decoupled manner. To enhance the ability of the robot assistant to perform anteversion and retroversion motions, the motorized uterus manipulator is designed. The robot assistant is mounted to the operating table through the supporting stand. Results: A prototype of the robot assistant is built, and experiments are conducted to verify the performance of the prototype. It is shown that the prototype is able to respond to the user’s instructions accordingly and manipulates the uterus of a manikin to a desired position. Performances of robot manipulation and human manipulation are also compared. It is shown that the robot assistant can retain the manikin’s uterus in a specified position in a more stable manner. Conclusions: Our experimental study shows that the use of a robot is a feasible alternative to position the uterus. By using this type of system, costs can be reduced and safety can be improved.