A simple and novel hybrid robotic system for robot-assisted femur fracture reduction

Abstract

When performing femur fracture reduction surgery, both the patient and surgeon are exposed to a great amount of radiation, which is harmful to their health. In order to reduce such radiation from the usage of an image intensifier, various robots have been proposed for femur fracture reduction surgery. Most of these robots are based on serial architecture. The low transportable load and poor accuracy are both inherent in serial robots, which makes them inappropriate for femur fracture reduction. Some parallel robots based on the 'Stewart platform' have also been developed for femur fracture reduction, but their restricted workspace limits their applicability and accessibility. To balance the accuracy, payload and workspace, a new robot system is reported in this paper. The proposed robot system consists of a 2-d.o.f. device and a 6-d.o.f. hybrid robot. The 2-d.o.f. device is used for distraction, which requires a very large force. The hybrid robot is used to manipulate a bone fragment for alignment and fixation purposes. The hybrid robot possesses the characteristic of a Cartesian coordinate robot; all the movements of the actuators are linear, which makes its motion smooth for low-speed fracture reduction procedures. The forward and inverse kinematics of the proposed robot are analyzed. The analysis is much simpler compared to traditional serial manipulators and parallel Stewart platform robots. A prototype of the proposed system is made using a rapid fabrication system called Objet. The positioning accuracy of the proposed system is measured using a coordinate-measuring machine. The results show that the algorithms presented in this paper for the control of the robot are accurate and robust. © Koninklijke Brill NV, Leiden and The Robotics Society of Japan.