Sensor-Based Surgical Robotics

Nowadays, the treatment of choice for femoral shaft fractures is the minimally invasive technique of intramedullary nailing. Apart from its advantages, however, the technique also has a number of known shortcomings like a frequent occurrence of malaligned reductions, which may have a significant impact on the functional biomechanics and the rehabilitation process of the patient. The high X-ray exposure, especially for the operating team, is a second point, why it may be desirable to support this surgical procedure by sophisticated technical tools. An interdisciplinary research project between the Hannover Medical School and the Technical University of Braunschweig is investigating the applicability of robotized surgical procedures in this context.

The present thesis originates from this project and shows the potential of supporting surgeons by means of robotic assistant systems, which can perform the reduction process of broken bone fragments. First, the development of a telemanipulator system is presented, with which the reduction can be performed based on 2D and 3D imaging data. This system is evaluated using exposed bones as well as human specimens. Based on the experiences from the telemanipulator system, a new concept for a (semi-)automated robotized fracture reduction procedure is developed. First, the automated reduction computes a reduction trajectory, which minimizes additional traumatization of the patient's soft tissue and subsequently moves the robot along that trajectory utilizing skill primitives incorporating sensor guarded and sensor guided motions.

Furthermore, this work presents automated image analysis methods, enabling the use of a robot as a precise drill guidance tool. Apart from fracture reduction, the insertion of the intramedullary nail and the distal locking of the nail are further challenging operation tasks, which remarkably benefit from the integration of surgical navigation, computer assisted surgery, and robotics. In this context, a concept to integrate Petri-nets and skill primitives within the well-known "Model-View-Controller"-pattern is presented in order to achieve a reliable workflow, which is not limited to strictly sequential execution tasks.

It can be shown that the methods developed in this thesis can improve the precision of these surgical operations and at the same time reduce the X-ray exposure to the patient and the operating team.