11 th INTERNATIONAL SCIENTIFIC CONFERENCE NOVI SAD, SERBIA, SEPTEMBER 20-21, 2012 Vitković, N., Veselinović, M., Mišić, D., Manić, M., Trajanović, M., Mitković, M. GEOMETRICAL MODELS OF HUMAN BONES AND IMPLANTS, AND THEIR USAGE IN APPLICATION FOR PREOPERATIVE PLANNING IN ORTHOPEDICS Abstract: Geometrically accurate and anatomically correct three-dimensional geometric model(s) of human bones (or bone sections) and implants are essential for successful preoperative planning in orthopedic surgery. Such models are often used in various software systems for the preparation and control of surgical interventions. In this paper, the process of models’ creation and their usage in application for the preoperative planning in orthopedics are presented. Models are created by using reverse engineering techniques, CAD (CATIA) and 3D Content creation software (Blender). The application is web oriented, and developed with use of modern web technologies like HTML5 and WebGL. In relation to commercial and free software systems currently in use, this application has several advantages such as: implementation of adaptive geometrical models, the ability to work across multiple platforms, ease of installation and use, etc. Key words: geometrical models, bones, application, web, preoperative planning 1. INTRODUCTION In orthopedic surgery, but also in all other sub- branches of surgery, where there is need for preoperative planning or creation of customized implants (fixators), there is a specific requirement to know the exact geometrical model of the human bone. Therefore, it is very important to create geometry of the bone rapidly and accurately. Having such models, it is possible to build customized bone implants (fixators) using rapid prototyping technologies, or performing preoperative planning procedures in adequate applications. The classification and analysis of 3D modeling methods for the creation of human bones geometrical models are presented in [1]. This paper describes the study and the development of a script for a commercial software package (3ds Max) able to reconfigure the template model (deformable by Free Form Deformation method - FFD) of a femur starting from two orthogonal images representing the specific patient’s anatomy. Although this study provides an outstanding contribution to the research field, there are some drawbacks. First one is the semi-automatic image segmentation (X-ray images) which is always problematic due to previously known problems with the X-ray images (superposition, inaccurate patient positioning, artifacts, etc.). The parametric model presented in this paper is not limited to the input data from only one source, because parameter values can be acquired from any available medical imaging devices: CT, X-ray, MRI, ultrasound, etc. The second drawback is creation of the script for the application in only one software (3ds Max). The points model created by this method can be used in any 3D graphic application which works with cloud of points model(s). The 3D reconstruction process which is based on anatomical properties is presented in [2]. The purpose of this study is to create a 3D model of human femur by using multiple X-ray images and anatomical properties of the femur. For 3D reconstruction, firstly, the 2D shape and specific parameters of the bone are measured from X-ray images. Then, the corresponding CT model is modified as it follows: the axial scaling, shearing transformation and radial scaling. Findings presented in [1,2] are the basis for the development of method presented in this paper. In [3], the authors are trying to create composite bone model with possible bone part adaptation and replacement from generic database of bone models. This is a useful approach when 3D scanning methods are available, but for 2D scanning methods more precise and patient-adapted models are required. In [4], the authors suggest application of standard bone fracture models database and its implementation in application for planning orthopedic operations. In [4] good example of preoperative procedures and techniques is presented. 2. THE GEOMETRIC MODELS CREATION PROCESS The developed method contains three preparatory processes which must be performed in order to generate a valid geometrical model (surface, solid, parametric model) of the specific human bone, as presented in Fig. 1. The applied method for creating the human bone geometrical model is based on anatomical properties (anatomical model) and human bone morphology. Fig.1 Preparatory processes for geometrical models creation 539