The authors have developed an image-directed robotic system to augment the performance of human surgeons in precise bone machining procedures in orthopaedic surgery, initially targeted at cementless total hip replacement surgery. The total system consists of an interactive CT-based presurgical planning component and a surgical system consisting of a robot, redundant motion monitoring, and man-machine interface components. In vitro experiments conducted with this system have demonstrated an order-of-magnitude improvement in implant fit and placement accuracy, compared to standard manual preparation techniques. The first generation system described in this paper was used in a successful veterinary clinical trial on 26 dogs needing hip replacement surgery. It was the basis for subsequent development of a second-generation system that is now in human clinical trials.>

The authors describe the use of force feedback in a surgical robot system (ROBODOC). The application initially being addressed is total hip replacement (THR) surgery, where the robot must prepare a cavity in the femur for an artificial implant. In this system, force feedback is used to provide safety, tactile search capabilities, and an improved man-machine interface. Output of the force sensor is monitored by a safety processor, which initiates corrective action if any of several application-defined thresholds are exceeded. The robot is able to locate objects using guarded moves and force control (ball-in-cone strategy). In addition, the force control algorithm provides an intuitive man-machine interface which allows the surgeon to guide the robot by leading its tool to the desired location. An application of force control currently under development is described, where the force feedback is used to modify the cutter feed rate (force controlled velocity).>