Model-based reconstruction of human bones for surgical purposes is an upcoming field of research in informatics and kinematics. Tools for planning surgeries and real-time support require appropriate mathematical models for rendering, interacting and reconfiguration. It is our conviction that superquadrics offer this powerful mathematical modeling capability. Image-based data from MRI and X-ray examinations have to be extracted and gathered to 3Dpoint sets, which are afterwards fitted by superquadric-based models. The fitting process is complex and time-consuming. To solve this problem and to provide real-time simulation for surgical support, it is necessary to apply the knowledge of the expert user. This paper presents the concept and a prototypical implementation of an interactive system that involves the user in the fitting process to accelerate the calculation and enhance the resulting model.