Signature Robot: A Miniature Robot for Orthopaedic Surgery

Imperial College London’s first venture into orthopaedic robotic surgery was with a spinoff company called Acrobot Ltd. This was developed over many years, culminating in a series of uni-condylar knee replacement (UKR) surgery operations with excellent results [1]. Much was learned from this experience with many hardware iterations culminating in a trolley based cooperative system with 3 powered axes carrying a cutter that required large arm motions. To exploit the resulting know-how, a new company, Sig- nature Robot Ltd, was founded. This also uses a cooperative robot, but instead of being a “hands on” device, the cutter motor is held between the fingers while the wrist is supported comfortably on a robot platform. This gives excellent synergy, combining the sensitive finger control of the surgeon with the precision and safety constraints (‘active constraints’ [2]) of the robot. The small, light robot is clamped on a simple passive arm, as seen in Figure 1, which can be readily repositioned to access regions of the knee, e.g., the tibia and femur. This paper presents the design for Signature Robot and how it addresses the limitations of the Acrobot, the accuracy of the positioning of the end effector is then quantified using a kinematic calibration routine.