Active Constraints for Robotic Knee Surgery

After a brief introduction to medical robotics, the concept of an "Active Constraint" System used in a medical robot called Acrobot^reg is described. The technical details of the complete system are then outlined, including the pre-operative planner which incorporates 3D CT models together with CAD models of prostheses that can be used to plan the leg alignment, position the prostheses, plan the shape of the cuts required and generate the regions within which cuts must be constrained. The robotic system is also described, together with the methods for locating, clamping, cutting and monitoring the patient. An outline is given of the means by which the preoperative model is registered or aligned to the intra-operative position of the patient and of the robot, without the need for fiducial markers. A prospective randomised clinical trial is then described, in which the robotic system was used for uni-condylar knee replacement surgery and compared to a conventional minimally invasive surgery procedure. The post operative results of the trial are then described and compared to the pre-operative plan.