This paper discusses the design of a navigation system developed to assist surgeons in the procedures of Hip Resurfacing prosthesis surgeries. In conventional surgery, mechanical jigs are used to obtain a correct alignment for the metal prosthesis, however it is a very time consuming process. In order to solve this problem emerges a new robotic system, named HipRob. The system is composed by a pre-operative sub-system for planning the prosthesis correct alignment and a flexible robot to be co-manipulated by the surgeon during the drilling procedures on the femur head. The real-time navigation of this robotic system is based on the registration between the femur model, constructed from the CT scan, and the surface constructed with ultrasound images, acquired during the surgical procedures. Experimental results, performed in a femur phantom, show that the robot location errors are around 2 mm.
