Abstract:

In severe fracture cases, a bone can be completely separated into two fragments. In order to guarantee a re-ossification of the bone, it is mandatory to reposition the bone fragment together. This process requires a delicate surgery called “bone reduction surgery”. Originally, the operation consisted in manipulating the bones fragments by hand in open surgery. But the development of intra-operative imaging, it has been then possible to perform a minimally invasive version of this type of operations. The most advanced technique rely on the use of a robotic manipulator to manipulate the bone fragment with higher precision and stability. The state of the art of this field is still limited as it is relatively recent compared to general medical robotics. Moreover, the diversity of mechanical architecture used for existing prototypes is also limited and they do not seem to result from a studies focused on the kinematic aspects.

This objective of this project proposal is to design a new robotic system dedicated to bone reduction surgery. For the design of the robotic manipulator, a new mechanical architecture is proposed. It is based on a 3-RPS parallel mechanism combined with a double-triangle hexagonal star composed two combinations of RPS. After the complete analysis of this mechanism, its optimization will be based on the kinematic performance, and the force transmission as criteria to optimize and on the minimum required workspace and minimum required force interaction as constraints.

The kinematic specification associated with the bone reduction surgery will be obtained from a series of simulations performed on a locally programmed software dedicated to preplanning reduction surgery, namely PhysiGuide. These simulations will be based on real patients’ data provided by our medical collaborator. The force interaction generated by the patient’s muscular tissue on the bone fragments will be provided by our medical collaborator. Once manufactured, a series of experiment will be performed on the robotic prototype in order to verify its ability to generate the appropriate trajectories issued by the PhysiGuide software. The prototype will be also tested on its ability to counter balance the force interaction of the muscular tissues. A specific platform composed of bone models attached with adjustable cables and springs will be designed and mounted in this regards.