PhD Position in Time-lapsed Imaging and Multiscale Modeling of Human Bone Fracture Healing

The aim of the research is to perform time-lapsed high-resolution CT imaging and multiscale modeling of distal radius bone fractures in patients and to investigate the in vivo healing process employing image processing and analysis. Bone fractures are very common and in 5-10% of the cases do not heal or are delayed. Nevertheless, factors influencing the healing outcome are not yet well understood. The specific aims of this PhD project will therefore be (1) to develop image analysis and registration methods to determine in vivo bone resorption and formation sites during fracture healing at the human distal radius, (2) to assess local bone remodeling and comparing the results with clinical biomarker measurements including whole bone strength through multiscale modeling approaches, and (3) to evaluate how bone remodeling during fracture healing affects whole bone strength in healthy, aged and osteoporotic humans.

The position will be based at the Inselspital Bern and at ETH Zurich, where the candidate will be enrolled in the Doctorate Program. Furthermore, this PhD project is embedded in a larger effort funded by the National Science Foundations of Switzerland, Germany, and Austria through a DACH consortium grant consisting of Ulm University (D), the Medical University Innsbruck (A), and the Inselspital Bern and ETH Zurich (CH). The overall goal of the consortium is to investigate local bone remodeling and mechanoregulation of bone fracture healing in healthy, aged, and osteoporotic humans.

The successful candidate holds or will soon receive a master’s degree in Biomedical, Electrical or Mechanical Engineering, and has preferentially a background in imaging and image processing. It is essential that the candidate is willing and motivated to work at the interface between engineering and clinical research. Additionally, excellent communication skills in English (oral and written) are required. Knowledge of German is advantageous for the clinical interactions but not absolutely required.

We look forward to receiving your online application includinga a motivation letter, CV, university transcripts and names and contact details of two references. Please note that we exclusively accept applications submitted through our online application portal. Applications via email or postal services will not be considered.

For further information about the group please visit our website www.bone.ethz.ch. Questions regarding the position should be directed to Dr. Patrik Christen by email patrik.christen[at]hest.ethz.ch (no applications).

Application

https://apply.refline.ch/845721/5964/index.html?cid=1&lang=en

PhD Position: Contribution to the improvement of a FE neck model for robust and bio-fidelic simulations

Context

The LBMC develops 3D Finite Element (FE) models to study the behaviour of the human body for applications in crash injury risk assessment, ergonomics and clinical orthopaedics. In these last two contexts, LBMC’s ‘Biomechanics and Ergonomics’ and ‘Biomechanics and Orthopaedics’ research teams have been developing subject-specific musculoskeletal models that aim at representing a virtual subject together with its physiological or pathological state. The EC funded DEMU2NECK project resulted in the development of a detailed FE model of the human neck within this framework. Results from this work allowed to identify the potential benefits of modelling 3D muscular actions (as opposed to 1D lines of action as is currently the case) to better account for the complex biomechanical loading that takes place within the cervical spine during tasks of the daily life. This potential may especially concern our ability to better model subject-specific characteristics, including for example a possible degradation of the muscular functional capacity resulting from either pathology or ageing. Benefits may thus be expected within applications regarding the assistance to the design of medical devices such as spinal implants and prostheses, by contributing to foster the development of ‘in-silico’ clinical trials, but also through the transfer towards applications related to ergonomics or virtual testing for the injury risk assessment of the vehicle occupant in poorly defined out-of-position scenarios (e.g. to better account for the driver’s postural behaviour in a pre-crash phase in the case of future autonomous vehicles).

Objectives

In order to support the development of such applications and ultimately of their use within virtual biomechanical or clinical trials, it is necessary to pursue the work already initiated to ensure the robustness of the active muscle model. This work targets both the numerical verification and the model validation as part of a VV&UQ (Verification Validation and Uncertainty Quantification) framework that is currently developed at LBMC trough a formalised multi-team research effort on the topic. This effort is also supported by Ifsttar through the funding of a MSc student industry placement at LBMC.

The PhD Thesis work will thus focus on the following objectives:

– Improve the robustness of the FE neck muscle model. Accounting for the active part of the muscle in a FE model remains a novel and challenging task, and this objective forms the core of the expected exploratory research and dissemination work. It may target several aspects:

• The evaluation and improvement of the mechanical formulation and implementation of the active muscle model currently implemented in the LSDyna FE code (i.e. a coupled passive 3D matrix/1D active Hill-type elements),
• The evaluation and estimation of task-related patterns of activation/muscle force distributions through a parallel FE/rigid-body co-simulation calculation loop,
• The contribution to the gathering of dynamic in-vivo muscle validation data to help better validate the above predicted muscle force distributions. –

– Further pursue the integration of the subject-specific geometric personalizing approaches that have already been developed at LBMC, for use with medical imaging,

– Further improve the validation and bio-fidelity of the model, and apply it to the study of case-studies of pathologies (such as degenerative muscular pathology or cervical dystonia) and to the comparative predictive evaluation of a range of technical or surgical designs used in cervical arthrodesis or arthroplasty.

Keywords

Modelling, Finite-Element, VV&UQ, Musculoskeletal, Spine, Cervical spine, Muscle, Simulation.

Examples of previous work on the topic

Howley, S. Développement et approche de personnalisation d’un modèle numérique musculaire déformable du cou, Thèse de Doctorat, Université de Lyon, 2014.

Fréchède, B, Kamdem Joutsa, F, Dumas, R. 2016. Multi-objective optimisation to assess muscle forces in a musculoskeletal model of the cervical spine. 22nd Congress of the European Society of Biomechanics ESB2016, July 10-13 2016, Lyon, France

Supervision, team and equipment

The student will be hosted within the ‘Biomechanics and Orthopaedics’ team. He/she will be jointly supervised by two researchers holding complementary expertise in FE and rigid-body dynamics modelling, as well as having positive experience of several co-supervisions on the topic. Equipment includes access to both HyperWorks/Radioss and LSDyna licenses, as well as to Lyon 1 University Department of Mechanics’ P2CHPD calculation cluster.

PhD candidate selection criteria

He/she will hold a MSc (or equivalent) in Mechanics or Mechanical Engineering with excellent results. He/she will also present some relevant prior experience with FE and/or rigid-body modelling as well as some good practical knowledge and strong interest in coding (Matlab, Scilab, Python). A background in biomechanics will be a strong plus for the application.

Application Applications should be made through the following website, where further information is also provided:

https://www.abg.asso.fr/fr/candidatOffres/show/id_offre/75559