Participants: This project was funded through ICube’s internal call. I am the coordinator of the project, which allowed me to set up a collaboration with Daniel Baumgartner, Senior Lecturer in the MMB team. Finally, Matthieu Ehlinger, Orthopedic Surgeon who joined ICube, allowed us to better define the needs and issues of the medical side.

Project summary: In a context of aging of the population, there is an increase in the number of fractures of the femur and orthopedic pathology. Surgical treatment imposes more and more frequently prosthesis installationsnincluding the possibility of a orosthesis of the enee and hip on the same lower limb. This (these) prosthesis necessarily modifies the distribution of the stresses in the bone structures, with the risk of zones of fragility. This significantly increases the risk of fracturesfafterwards. These so-called periprosthetic fractures and worst interprothetic fractures represent a real surgical challenge. In this project, we propose to use numerical simulationsoto analyze stresses and deformations within the material depending on the placement of the implants. This mechanical analysis of femoral constraints aims to highlight the peaks of femoral stresses and deformities between prostheses, in order to provide surgeons with an objective tool to determine the minimum length to respect between two prostheses.

This project is part of the transverse axis Imaging and Medical and Surgical Robotics (IRMC) and Materials Engineering for Energy and the Environment (IMEE) of the ICube laboratory. Obtaining CT scan of non-fractured femurs, but wearing a prosthesis poses several technological problems. First of all because of the presence of a metal structure (the prosthesis) that causes a lot of artifacts in the images. In addition, the acquisition of a CT scan of a prosthetic femur bone, but not fractured, is very rare since usually CT is performed at the time of the patient’s arrival at the hospital, when the bone is already fractured. We therefore proposed a protocol for the validation of our models. From 3 fractured femur scanners on patients wearing a prosthesis before the fall, we segmented the structures with the help of Matthieu Ehlinger who helped us to recognize the anatomical structures in the areas with the most artifacts. From the fractured model, we then developed an algorithm that allows repositioning the bone in an anatomical configuration before the fracture (see Figure 5).

Our objective was then to propose a validated model of femur fracture that takes into account the mechanics of the prosthesis. For this, we proposed a classification of fall scenarios leading to a fracture. Each scenario was modeled in the commercial simulation software ALTAIR HYPERWORKS and the results were compared and validated with the clinical data. The models are parameterized in accordance with Daniel Baumgartner’s previous work [ABWG14] for the simulation of shocks on the skull.

Publications: This work resulted in a publication [ECFD17].