Development of a femur fracture reduction robot

This paper describes a novel robot system for fracture reduction of a femur with a reduction path navigation system based on 3D CT image modeling. The robot has 6-degrees-of-freedom to realize fracture reduction motion with a mechanical failsafe mechanism as well as a software failsafe. Furthermore, one 6-axis force sensor is installed to realize power assist capability for a doctor as well as to measure the force applying on the patient´s femur. Three of the operation modes necessary for fracture reduction operation are introduced, i.e., a JOG operation mode, a power assist mode and an automatic operation mode. The control method of the power assist mode by means of one force sensor is proposed and explained in detail. Furthermore, the control method of the automatic operation mode is described to correspond with a real-time reduction path modification by the navigation system. Experiments are conducted to verify the failsafe function and accuracy of the motion control.