Cooperative robotic assistant with drill-by-wire end-effector for spinal fusion surgery

Abstract

Purpose - The purpose of this paper is to present a surgical robot for spinal fusion and its control framework that provides higher operation accuracy, greater flexibility of robot position control, and improved ergonomics. Design/methodology/approach - A human-guided robot for the spinal fusion surgery has been developed with a dexterous end-effector that is capable of high-speed drilling for cortical layer gimleting and tele-operated insertion of screws into the vertebrae. The end-effector is position-controlled by a five degrees-of-freedom robot body that has a kinematically closed structure to withstand strong reaction force occurring in the surgery. The robot also allows the surgeon to control cooperatively the position and orientation of the end-effector in order to provide maximum flexibility in exploiting his or her expertise. Also incorporated for improved safety is a "drill-by-wire" mechanism wherein a screw is tele-drilled by the surgeon in a mechanically decoupled master/slave system. Finally, a torque-rendering algorithm that adds synthetic open-loop high-frequency components on feedback torque increases the realism of tele-drilling in the screw-by-wire mechanism. Findings - Experimental results indicated that this assistive robot for spinal fusion performs drilling tasks within the static regulation errors less than 0.1 mu m for position control and less than 0.05 degrees for orientation control. The users of the tele-drilling reported subjectively that they experienced torque feedback similar to that of direct screw insertion. Research limitations/implications - Although the robotic surgery system itself has been developed, integration with surgery planning and tracking systems is ongoing. Thus, the screw insertion accuracy of a whole surgery system with the assistive robot is to be investigated in the near future. Originality/value - The paper arguably pioneers the dexterous end-effector appropriately designed for spinal fusion, the cooperative robot position-control algorithm, the screw-by-wire mechanism for indirect screw insertion, and the torque-rendering algorithm for more realistic torque feedback. in particular, the system has the potential of circumventing the screw-loosening problem, a common defect in the conventional surgeon-operated or robot-assisted spinal fusion surgery.