Robotic System for Accurate Minimally Invasive Laser Osteotomy

Bone cutting, so-called osteotomy, is an essential part of many surgical procedures. Nowadays, bone cutting is mainly performed using mechanical devices such as milling cutters, drills, and saws. Laser osteotomy is a novel alternative for cutting bone with several advantages compared to conventional methods. Existing devices for cutting bone with laser require direct access to the entire bone, i.e., are not minimally invasive. This work is part of an overall project called Minimally Invasive Robot-Assisted Computer-guided LaserosteotomE (MIRACLE), aiming to make minimally invasive bone cutting possible. In an initial application, we are developing a device for use in minimally invasive unicondylar knee arthroplasty (UKA). This thesis focuses on the challenges of the MIRACLE project in robotics and presents a robotic device for minimally invasive bone cutting. One of the main challenges in developing such a device is to achieve the desired high positioning accuracy of the laser with a dexterous device with a small diameter. Typically, high accuracy requirements are met by large, rigid robotic structures with minimal degrees of freedom. I present a concept for positioning the laser at the surgical site that enables minimally invasive surgery: an overall robotic system consisting of different components, each fulfilling a subset of the requirements. Combined into a complete system, the realization of high accuracy laser positioning using a small diameter surgical instrument with high dexterity will become possible. The system components include: i) a bone-mounted miniature parallel robot that positions the laser, which is mounted at the tip of a ii) small diameter robotic endoscope with several degrees of freedom, allowing for minimally invasive insertion. For safe, intuitive, and accurate handling, the robotic endoscope is mounted on and guided by a iii) large robotic manipulator. I designed, developed, and evaluated prototypes of the miniature robot and the robotic endoscope, combined them with a large manipulator and showed the first proof of concept of the whole mechanical system. The results of this work suggest that the requirements for the robotic system depend heavily on the limitations of the other system components (e.g., the cutting laser) and that the robotic system is currently not the limiting factor for the realization of minimally invasive UKA using laser osteotomy.