Safety and Accuracy Considerations in Developing a Small Sterilizable Robot for Orthopaedic Surgery

The objective of this work was to design a compact, accurate, safe, and ease-to-use surgical robot for total knee arthroplasty. The goal of the bone-mounted robot, named Praxiteles, is to precisely position a surgical bone-cutting guide in the appropriate planes surrounding the knee, so that the surgeon can perform the cuts manually using the guide. The robot architecture is comprised of 2 motorized degrees of freedom (DOF) whose axes of rotation are arranged in parallel, and are precisely aligned to the implant cutting planes with a 2 DOF serial adjustment mechanism. An initial prototype was first developed and tested on saw bones and cadavers, and construction of a new, refined version is now well underway. A backdrivable system, with high-stiffness, high-precision static positioning capabilities and safe low-force dynamic movement is achieved using a quick-release, spring-loaded mechanical braking system integrated in a gear transmission unit at the level of the motor outputs. This paper discusses the technical challenges encountered during the development, design, and construction of the system.