Processes in living bone lead to structural changes on different length and time scales. Bone is constantly renewed due to bone remodeling, where in an interplay between bone-resorbing and bone-forming cells, a microscopic part of the bone is locally replaced. The initially formed soft bone is stiffened by the incorporation of mineral particles in the organic matrix during a process of mineralization. After bone fracture, a third process becomes active. Bone healing does not lead only to a restoration of the mechanical function of bone, but enables a return to the pre-fractured state.
In our research group the processes of bone healing, remodeling and mineralization are investigated using mathematical modeling and computer simulation. The computational work mainly pursues three aims: i) to quantitatively describe how these processes are controlled. Remodeling and healing are thought to be controlled by local mechanical forces acting on cells in the bone tissue – they are so-called mechanobiological processes. Hypotheses of how cells react to mechanical forces are implemented in phenomenological models, and the resulting computed bone structure is then compared with experimental observations; ii) to predict changes in bone structure as a result of aging, diseases and pharmaceutical treatment; iii) to extract nontrivial information about the underlying processes from experimental data, which can provide only a snapshot of the bone structure.
The computational investigations are performed in close connection with experimentalists, who provided structural bone data in the form of histological sections of the bone fracture callus, micro-computed tomography (μ-CT) images of the trabecular bone architecture, and quantitative backscattered electron images (qBEI) of the mineral heterogeneity of bone. The computer models are constructed with respect to the available experimental data. This allows a direct comparison between experimental evidence and computational predictions to validate the used models.
Beside the computational work, an experimental characterization of bone and biological materials is performed in our group. We use Scanning Acoustic Microscopy (SAM) to map information about the mechanical properties and the density of bone and other biological materials. On the nanoscopic length scale, spectroscopic methods provide information about the composite of collagen molecules and mineral particles in bone. Spectroscopic experiments performed at the synchrotron BESSY in Berlin are complemented by atomistic Molecular Dynamics (MD) simulations to help interpreting the measured spectra.