Collaborative Drill Alignment in Surgical Robotics

--Robotic assistance allows surgeries to be reliably and accurately executed while still under direct supervision of the surgeon, combining the strengths of robotic technology with the surgeon's expertise. This paper describes a robotic system designed to assist in surgical procedures by implementing a virtual drill guide. The controller constrains the tool to the desired axis, while allowing axial motion to remain under the surgeon's control. Compared to prior virtual-fixture approaches--which primarily perform pure energy-shaping and damping injection with linear springs and dampers-our controller uses a virtual prismatic joint to which the robot is constrained by nonlinear springs, allowing us to easily shape the dynamics of the system. We detail the calibration procedures required to achieve sufficient precision, and describe the implementation of the controller . We apply this system to a veterinary procedure: drilling for transcondylar screw placement in dogs. The results of the trials on 3D-printed bone models demonstrate sufficient precision to perform the procedure and suggest improved angular accuracy and reduced exit translation errors compared to patient specific guides (PSG). Discussion and future improvements follow. OBOTIC surgery has many potential advantages for treatment of humeral intracondylar fissure in dogs: these include enhanced precision, accuracy and reliability. We propose a robotic system to assist with drilling in preparation for transcondylar screw placement [1]. The novelty of our approach is to cast the problem into the setting of collaborative robotics: replacing the physical guide with a virtual one, combining the skills of the surgeon with the precision of the robot, and implementing this in an interactive way, not obscured by teleoperation or taken out of the surgeons hands by automation. We ask: can a mechanical drill guide be replaced by a virtual-drill guide, enforced by the robot? How can a controller be designed to implement such a behaviour? Can we show that the performance/accuracy of this system is sufficient and compares favourably to other methods? We will contrast our approach with a state-of-the-art assistive technology: 3D printed Patient-Specific-Guides (PSGs).