Bone remodeling: multiscale mechanical models and multiphysical aspects

Bone as a mechanical structure combines outstanding properties, such as high mechanical strength with low weight, adaptability of its microstructure and shape to changes in mechanical loading, ability to repair after a fracture, and long service life. Despite the many studies devoted to the mechanisms controlling the process of bone formation and renewal, a clear understanding of the underlying mechanisms across the scales and the role of mechanical loading is still not available. Bone is multiscale in nature and the tissue integrity is maintained across large length and time scales by complex multiscale multiphysical homeostatic processes regulated by specialized cells. Since these are difficult to identify based purely on experiments, it is important to develop multiscale computational approaches in combination with the acquisition of new experimental data obtained by efficient imaging techniques allow to integrate and investigate these processes. A bone has the ability to adapt its external shape and internal structure to variations in its mechanical environment. The adaptive response of bones to changes in load history is called bone remodeling since the pioneering work of Wolff (1892): skeletal elements are placed to optimize strength in relation to the applied loading distribution, and the mass of those skeletal elements is in direct relation to the magnitude of the applied loading. Adaptation of bone to functional demands such as mechanical loadings may result in bone loss in situations of reduced loading, and bone mass increase in situations when functional mechanical loadings exceed a certain magnitude. Models developed in the literature to simulate the functional adaptation of bone fall into three main classes having each a specific modeling approach: optimization, phenomenological and mechanistic models. Optimization theories envisage bone as a mechanical structure undergoing an evolutionary adaptation. Phenomenological models provide a quantitative description of the bone response under a given stimulus, but they do not provide an understanding of the biological processes of functional adaptation. The consideration of those processes is the object of mechanistic models, which have the ability to incorporate the chemical and biological mechanisms involved in the modification of bone architecture and properties. The objective of the Colloquium is to bring together researchers amongst the computational and experimental mechanics and biomechanics community to exchange the latest achievements as well as recent research work in the field of bone mechanical research. The Colloquium shall provide state-of-the-art information in the domain of bone mechanics, focusing on bone remodeling and bone adaptation as a core topic. Themes of interest include the development of multiscale and multiphysical computational models for bone remodeling, adaptation and healing, interactions between bone damage and remodeling, high resolution imaging techniques, micromechanical models to estimate the tissue mechanical properties, topology and shape optimization approaches to predict bone microstructures, computational and algorithmic aspects, model verification and validation by experiments, mechano-transduction of bone remodeling, phenomena occurring at the interface between bone implants and biosubstitutes, the development of patient-specific predictive models and treatments.