Simulation of tissue differentiation during fracture healing.
Abstract (summary)
Fracture healing is a complex biological process during which, repair of the damaged tissues occurs so efficiently that the initial strength and anatomy of the bone are restored. Mechanical loading is believed to greatly influence the extent to which repair is accelerated or delayed.
An iterative algorithm based on a mechano-regulation concept was developed to simulate tissue differentiation during fracture healing. It is based on the calculation of two mechanical stimuli; octahedral shear strain and fluid flow, using a poroelastic finite element model. Proliferation of progenitor cells was accounted for. Depending on cell concentration and on predicted mechanical stimuli, cell differentiation was simulated for various fracture healing cases. Cell origin, load magnitude, fracture gap size, bending load, fracture type and a realistic 3D model were investigated.
The main phases observed during fracture healing were predicted. Fracture gap size and loading had a large influence on the healing patterns and mechanical stimuli. A bending load increased the amount of displacement and thereby delayed fracture healing. An oblique fracture was predicted to increase tissue shearing. A 3D fracture model showed the non-symmetric distribution of mechanical stimuli within the callus.
The model has successfully simulated tissue differentiation during fracture healing for various clinical cases. The stability of the algorithm and the use of fixed input parameters throughout the study, indicate that this concept may be applied to other problems in mechano-biology.