THE GEOMETRICAL MODELS OF THE HUMAN FEMUR AND ITS USAGE IN APPLICATION FOR PREOPERATIVE PLANNING IN ORTHOPEDICS Nikola Vitković 1 , Miroslav Trajanović 1 , Jelena Milovanović 1 , Nikola Korunović 1 , Stojanka Arsić 2 , Dragana Ilić 3 1 University of Niš, Faculty of Mechanical Engineering in Niš 2 University of Niš, Faculty of Medicine in Niš 3 Clinical Center Niš Abstract: In this paper two types of human femur geometrical models and method for its creation are presented. Created method is developed with respect to the morphological and anatomical properties of the human femur, and it enables forming of parametric polygonal mesh and decriptive XML models. The parametric mesh model is based on two parameters, acquired from medical imaging method (CT, X-ray). The first parameter is determined as distance between most prominent points on epicondyles – Df, and the second one as distance between line conecting the most prominent points of epicondyles and the center of the femoral head – FHA. The purpose of the polygonal mesh model is to improve the preparation of orthopedic surgeries and make it easier. The aim of XML model is to enable exchange of mesh model data between applications in network environment. The presented models are applied in the application for preoperative planning, developed by the authors. 1. INTRODUCTION 1.1 The goal of the research The goal of present research is creation of digital representation of the human femur, which will be employed in the Application for Preoperative Planning in Orthopedics (APPO). This representation will enable exchange of model data between APPO applications or between different types of medical imaging devices (X-ray, CT, MRI) and APPOs. For this purpose two models have been created. The first one is Parametric polygonal Mesh Model (PMM), which describes geometry and topology of the human femur, and the second one is Orthopedics XML Model for oPerations (OXMP). The XML word refers to the well known specification of the rules for creating (describing) data structures, used for sharing data over the network (LAN, Internet) by various types of applications. In this case XML is used as a tool for describing data about mesh geometry (descriptive geometrical model), patient-relevant data, etc 1.2 The previous work The PMM and OXMP models have been defined during the process of APPO development. The parametric mesh model is able to adapt its geometry and topology to the real human femur by employing adequate parameter values which can be acquired from the medical images (CT, MRI, X-ray). In earlier stages of work, implementation of this parametric model was restricted to the APPO at one workstation. The transfer of mesh model data or parameter values between different workstations was possible only via some kind of media storage. For this reason OXMP model was developed and applied in the APPO. 1.3 The possible benefits The use of developed models in medicine and technology can bring considerable benefits. The most important characteristic of PMM is its ability to conform to the individual human femur geometry and topology, which brings great benefits in a sense of: application in the software for preoperative planning, detail analysis and collation with medical images (CT, MRI, X-ray), creation of solid model for use in FEA, RP fabrication of implant prototypes, making presentation models, etc. 1.4 The brief review of research in this field Several attempts to create adequate bone models, in a sense of its implementation in preoperative planning, have been made. Matthews and coworkers in [1] presented composite bone model with possible bone segment adaptation and replacement from the generic database of the bone models. This is an useful approach when 3D scanning devices are available. For 2D scanning more precise and patient-adapted models are required. Sourina and coworkers in [2] suggest application of standard bone fracture models database and its implementation in application for planning orthopedic surgeries (PC application). This and the previous approach [1] do not cover all possibilities of the bone pathology (bone fractures being just one of them). The main difference between applied technique and the other mentioned above is the way geometrical model are created. The presented model is generated according to the acquired parameters from the medical imaging methods, and no database of generated bone models is used. Transferring data (image data, model data) in medicine can be achieved by using known standards and techniques (like PACS - picture archiving and communication systems); however, they use different approach to access relevant information about medical images, as it is described in [3, 4], although PACS can be used for acquiring parameter values. The proposed system for data exchange (OXMP) is more simple and possibly faster and easier to use. 2. THE GEOMETRICAL MODELS OF THE HUMAN FEMUR 2.1 The Parametric polygonal mesh model (PMM) The most important goal of this research is to find the best possible solution or method for creation of parametric femur