Debonding of coin-shaped osseointegrated implants: Coupling of experimental and numerical approaches.

While cementless implants are now widely used clinically, implant debonding still occur and is difficult to anticipate. Assessing the biomechanical strength of the bone-implant interface can help improving the understanding of osseointegration phenomena and thus preventing surgical failures. A dedicated and standardized implant model was considered.

Modeling the debonding process of osseointegrated implants due to coupled adhesion and friction.

Cementless implants have become widely used for total hip replacement surgery. The long-term stability of these implants is achieved by bone growing around and into the rough surface of the implant, a process called osseointegration. However, debonding of the bone-implant interface can still occur due to aseptic implant loosening and insufficient osseointegration, which may have dramatic consequences.

Determinants of the primary stability of cementless acetabular cup implants: A 3D finite element study.

Primary stability of cementless implants is crucial for the surgical success and long-term stability. However, primary stability is difficult to quantify in vivo and the biomechanical phenomena occurring during the press-fit insertion of an acetabular cup (AC) implant are still poorly understood. The aim of this study is to investigate the influence of the cortical and trabecular bone Young's moduli E and E, the interference fit IF and the sliding friction coefficient of the bone-implant interface μ on the primary stability of an AC implant.

Nonaxisymmetric Shapes of Biological Membranes from Locally Induced Curvature.

In various biological processes such as endocytosis and caveolae formation, the cell membrane is locally deformed into curved morphologies. Previous models to study membrane morphologies resulting from locally induced curvature often only consider the possibility of axisymmetric shapes-an indeed unphysical constraint. Past studies predict that the cell membrane buds at low resting tensions and stalls at a flat pit at high resting tensions.

A modified Coulomb's law for the tangential debonding of osseointegrated implants.

Cementless implants are widely used in orthopedic and dental surgery. However, debonding-related failure still occurs at the bone-implant interface. It remains difficult to predict such implant failure since the underlying osseointegration phenomena are still poorly understood.

Irreversible thermodynamics of curved lipid membranes.

The theory of irreversible thermodynamics for arbitrarily curved lipid membranes is presented here. The coupling between elastic bending and irreversible processes such as intramembrane lipid flow, intramembrane phase transitions, and protein binding and diffusion is studied. The forms of the entropy production for the irreversible processes are obtained, and the corresponding thermodynamic forces and fluxes are identified.

Efficient isogeometric thin shell formulations for soft biological materials.

This paper presents three different constitutive approaches to model thin rotation-free shells based on the Kirchhoff-Love hypothesis. One approach is based on numerical integration through the shell thickness while the other two approaches do not need any numerical integration and so they are computationally more efficient. The formulation is designed for large deformations and allows for geometrical and material nonlinearities, which makes it very suitable for the modeling of soft tissues.

A projection method to extract biological membrane models from 3D material models.

This paper presents a projection method for deriving membrane models from the corresponding three-dimensional material models. As a particular example the anisotropic Holzapfel-Gasser-Ogden model is considered. The projection procedure is based on the kinematical and constitutive assumptions of a general membrane theory, considering the membrane to be a general two-dimensional manifold.

A detailed 3D finite element analysis of the peeling behaviour of a gecko spatula.

This paper presents a detailed finite element analysis of the adhesion of a gecko spatula. The gecko spatulae form the tips of the gecko foot hairs that transfer the adhesional and frictional forces between substrate and foot. The analysis is based on a parameterised description of the 3D geometry of the spatula that only requires 12 parameters.

Multiscale modelling and simulation of the deformation and adhesion of a single gecko seta.

A 3D multiscale model is presented which describes the adhesion and deformation of a gecko seta. The multiscale approach combines three models at different length scales: at the top level, on the order of several micrometers, a nonlinear finite element beam model is chosen to capture the branched microstructure of the gecko seta. At the intermediate level, on the order of several nanometers, a second finite element model is used to capture the detailed behaviour of the seta tips, the so-called spatulae.

An atomistically enriched continuum model for nanoscale contact mechanics and its application to contact scaling.

This work provides a comprehensive exposition and extension of an atomistically enriched contact mechanics model initially proposed by the present authors. The contact model is based on the coarse-graining of the interaction occurring between the molecules of the contacting bodies. As these bodies may be highly compliant, a geometrically nonlinear kinematical description is chosen.