Jerome Noailly
Jérôme Noailly holds a Bachelor degree in Physical Chemistry, an Engineer and a Master degree in Material Science, and a Master degree in Acoustics. In 2002, he started a PhD in spine computational biomechanics at the Universitat Politècnica de Catalunya, Barcelona (UPC), Spain and mainly focussed on the development and validation of the most critical theoretical approximations towards reliable models for the exploration of the internal biomechanics of the lumbar spine. In 2009, his work received the Best PhD Thesis award in Engineering from the UPC. In 2006 Jérôme was awarded a Marie Skłodowska-Curie fellowship (MECNOR-MEIF-CT-2006-518768) and worked in computational mechanobiology and hydrogel mechanics for cartilage tissue engineering at the AO Research Institute (AO Foundation, Davos, Switzerland) and at the Eindhoven University of Technology (The Netherlands). In 2009, he went back to Barcelona with a Marie Skłodowska-Curie reintegration grant (SEVBIOM-PERG05-GA-2009-249210) and retook spine modelling activities at the Institute for Bioengineering of Catalonia (IBEC), Barcelona, Spain. In 2010, Jérôme co-led a sucessful European research proposal, My Spine (FP7-269909), and in 2012 he became the head of the Biomechanics and Mechanobiology group at IBEC. From 2012 to 2015, he expanded the research of the group to the field of computational systems biology, in the framework of the European project The Grail (FP7-278557).In 2015, Jérôme relocated at the Universitat Pompeu Fabra (UPF), along with his team, in his quality as principal investigator of the Multiscale and Computational Biomechanics and Mechanobiology (MBIOMM) group (2014-SGR-1616). As a member of the Department of Information and Communication Technologies and SIMBIOSys group at UPF, he generated synergies to integrate medical image analysis and machine learning dimensions into the MBIOMM activities. At the same time, he was consolidating the combination of computational systems biology approaches and biomechanical /multiphysics modelling, for multiscale explorations of tissues and organs, in health and disease. In 2016, Jérôme was awarded a Ramon y Cajal fellowship (RYC-2015-18888) from the Spanish government, and he is currently the Principal Investigator of the Biomechanics and Mechanobiology Area of the Barcelona Centre for New Medical Technologies (BCN MedTech- 2017-SGR-1386).Jérôme has been professor in materials technology and material mechanics at the UPC, and he is teaching continuum mechanics, biomaterials and musculoskeletal system modelling at the UPF, Barcelona, Spain. He is member of the Council of the European Society of Biomechanics (ESB), past president of the Spanish National Chapter of the ESB (CAP-ESB), and Chair of the PhD and Award Committees of the Virtual Physiological Human Institute (VPHi).
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In Chapter 2, a L3-L5 lumbar spine bi-segment model was built. An initial model was completed to include the vertebral cortex, a full definition of the facet joints, the cartilage endplates, and an improved description of the annulus fibre-reinforced structure. Simplified load-cases used for in vitro studies were simulated to calculate stress and strain energy distributions. Predictions within the L3-L5 lumbar spine bi-segment model could be interpreted in terms of functional load distributions related to known tissue structures, but the overall L3-L5 bisegment model geometry needed further update.
Thus, in Chapter 3, a geometrically accurate L3-L5 lumbar spine bi-segment model was created. The new model included corrected L3 and L5 body shapes and dimensions, corrected disc heights and nucleus placements, corrected posterior bone shapes, dimensions, and orientations, and corrected ligament distributions. The new and old geometries were biomechanically compared. Results showed that the relative roles of modelled tissues greatly depend on the geometry. Predicted load distributions were generally more physiological in the new model. However, new and old models could both reproduce experimental ranges of motion, meaning that their validation should take into account local load transfers.
Chapter 4 focuses on the variability of the annulus collagen criss-cross angles. Four bi-segment models with literature-based annulus fibre organizations were created and compared under diverse loads. Moreover, an annulus stabilization parameter was proposed by analogy to a thick walled pipe. Model biomechanics greatly depended on the annulus fibre organization, but annulus stabilization parameter was often contradictory with the predicted stresses and strains. Spine geometry and annulus fibrous organization were hypothesized to be linked together. Adapted annulus collagen networks may be numerically determined, but annulus modelling should be based on mechano-biological relationships.
In Chapter 5, a case-study of a novel artificial disc design coupled with the L3-L5 lumbar spine model is presented. Bi-segment models with and without implant were compared under load- or displacement-controlled rotations, with or without body-weight like load. Prosthesis stiffness generally altered the load distributions and displacement-controlled rotations led to strong adjacent level effects. Including body weight-like loads seemed to give more realistic results. Although the novel disc substitute is too stiff, it is more promising than other existing commercial devices.
In this thesis, six new osteoligamentous lumbar spine bi-segment finite element models were created. Simulations showed that reliable use of lumbar spine finite element models requires precise descriptions of local tissue loading and response. Local predictions were qualitatively mainly limited by a lack of knowledge about soft tissue structural organisations, constitutive equations, and boundary conditions. However, models can be used as in silico laboratories to overcome such limitations. A hierarchical procedure for the development of qualitatively reliable lumbar spine finite element models was proposed based on available numerical and experimental inputs.
Papers by Jerome Noailly
In Chapter 2, a L3-L5 lumbar spine bi-segment model was built. An initial model was completed to include the vertebral cortex, a full definition of the facet joints, the cartilage endplates, and an improved description of the annulus fibre-reinforced structure. Simplified load-cases used for in vitro studies were simulated to calculate stress and strain energy distributions. Predictions within the L3-L5 lumbar spine bi-segment model could be interpreted in terms of functional load distributions related to known tissue structures, but the overall L3-L5 bisegment model geometry needed further update.
Thus, in Chapter 3, a geometrically accurate L3-L5 lumbar spine bi-segment model was created. The new model included corrected L3 and L5 body shapes and dimensions, corrected disc heights and nucleus placements, corrected posterior bone shapes, dimensions, and orientations, and corrected ligament distributions. The new and old geometries were biomechanically compared. Results showed that the relative roles of modelled tissues greatly depend on the geometry. Predicted load distributions were generally more physiological in the new model. However, new and old models could both reproduce experimental ranges of motion, meaning that their validation should take into account local load transfers.
Chapter 4 focuses on the variability of the annulus collagen criss-cross angles. Four bi-segment models with literature-based annulus fibre organizations were created and compared under diverse loads. Moreover, an annulus stabilization parameter was proposed by analogy to a thick walled pipe. Model biomechanics greatly depended on the annulus fibre organization, but annulus stabilization parameter was often contradictory with the predicted stresses and strains. Spine geometry and annulus fibrous organization were hypothesized to be linked together. Adapted annulus collagen networks may be numerically determined, but annulus modelling should be based on mechano-biological relationships.
In Chapter 5, a case-study of a novel artificial disc design coupled with the L3-L5 lumbar spine model is presented. Bi-segment models with and without implant were compared under load- or displacement-controlled rotations, with or without body-weight like load. Prosthesis stiffness generally altered the load distributions and displacement-controlled rotations led to strong adjacent level effects. Including body weight-like loads seemed to give more realistic results. Although the novel disc substitute is too stiff, it is more promising than other existing commercial devices.
In this thesis, six new osteoligamentous lumbar spine bi-segment finite element models were created. Simulations showed that reliable use of lumbar spine finite element models requires precise descriptions of local tissue loading and response. Local predictions were qualitatively mainly limited by a lack of knowledge about soft tissue structural organisations, constitutive equations, and boundary conditions. However, models can be used as in silico laboratories to overcome such limitations. A hierarchical procedure for the development of qualitatively reliable lumbar spine finite element models was proposed based on available numerical and experimental inputs.
Hip arthritis is a pathology linked to hip-cartilage degeneration. Although the aetiology of this disease is not well defined, it is known that age is a determinant risk factor. However, hip arthritis in young patients could be largely promoted by biomechanical factors. The objective of this paper is to analyze the impact of some normal anatomical variations on the cartilage stress distributions numerically predicted at the hip joint during walking.
Methods
A three-dimensional finite element model of the femur and the pelvis with the most relevant axial components of muscle forces was used to simulate normal walking activity. The hip anatomical condition was defined by: neck shaft angle, femoral anteversion angle, and acetabular anteversion angle with a range of 110-130º, 0-20º, and 0-20º, respectively. The direct boundary method was used to simulate the hip contact.
Findings
The hydrostatic stress found at the cartilage and labrum showed that a ± 10º variation with respect to the reference brings significant differences between the anatomic models. Acetabular anteversion angle of 0º and femoral anteversion angle of 0º were the most affected anatomical conditions with values of hydrostatic stress in the cartilage near 5 MPa under compression.
Interpretation
Cartilage stresses and contact areas were equivalent to the results found in literature and the most critical anatomical regions in terms of tissue loads were in a good accordance with clinical evidence. Altogether, results showed that decreasing femoral or acetabular anteversion angles isolately causes a dramatic increase in cartilage loads.