Abstract:

In most several cases of fractures, a bone can be totally separated into two or more pieces. To ensure a proper re-ossification of the bone, it is necessary reposition the bone fragments in their original configuration first. This procedure is called bone reduction surgery. Nowadays, this intervention can rely on robotic systems to directly manipulate the patient’s bone fragment using minimally invasive procedure. This suppresses the risks associated with infection, bleeding and fragments misalignment. Most robots for bone reduction are based on hexapod Steward-Gough mechanism. But its limited workspace may cause difficult registration procedure during pre-operative phases. Also, the use of rigid circular rings reduces the flexibility for the installation of the surgical nails. A new concept of modular robotic leg is proposed to only increases the available workspace but also to provide more flexibility for the installation of the surgical nails.

Internal and external research have highlighted the great potential of augmented tripod concepts. Because of their ability to generate six Degrees of Freedom with only three legs, their workspace shows larger reach than classical StewardGough mechanisms of identical dimensions. Among other prototypes, a previous MOST (now NSTC) project from 2019 to 2021 has led to the design of a 3-RPSP mechanism that shows increased workspace and also a better adaptability to bone reduction surgery due to its specific architecture. The present project will focus on the design of a modular robotic manipulator for the same application. It will be based on the same augmented tripod mechanism while each of its leg will be mounted separately on the patient’s anatomy in order to facilitate the preoperative procedure. In this new concept, it is no longer necessary to align the inserted nails with a circular ring as it is no longer present. While guided through motion capture system, the insertion of nails can be carried out either freely or guided to a pre-identified location based on optimized robotic trajectories. Once all inserted, the modular robotic legs can then be mounted individually. The installation and registration procedure are defined to ensure that the operator is never exposed to radiative intra-operative image. 

As part of the project, two main tasks will be performed. The first one focuses on the kinematic analysis and the design of the modular robotic legs. While inspired from the previous prototype, major difference in the theoretical model resolution and anticipated due to the irregular geometry of the base and the end effector, which corresponds to the placement of nails. The second task consist in programming the user interface that ensure the different phase of the bone reduction surgery. Combined with a motion capture system operating in real time, the interface will perform the robot trajectory optimization, the nail insertion guidance and registration and tracking of the robotic legs operation. Operational prototypes of the modular robotic leg will be fabricated and experimentations will be carried out in a clinically simulated environment in order to validate the feasibility of the concept.