The general aim is to assist osteotomic surgery by the development of a virtual lab extending the Amira toolbox, which will then include data pre- and postprocessing, visualization, heterogeneous DAE/PDE modelling, and efficient numerical algorithms. We will start by deriving the detailed heterogeneous model and efficient numerical methods for the different human gaits. This requires a significant improvement of existing local models and dynamical simulation techniques for the biomechanical components - to be properly integrated within a global heterogeneous model. Detailed 3D FEM models of the tibia and of typical fracture fixation devices, incorporating contact and frictional effects, will be developed in close cooperation with the trauma and constructive surgeons G. Duda and N. Haas, ( Klinik für Unfall- und Wiederherstellungschirurgie der Charité). The final outcome will be an individual surgery plan.