Predictive geometrical model of the upper extremity of human fibula

Computer assisted preoperative planning in orthopedic surgery, as well as designing and manufacturing of personalized fixators, implants and scaffolds requires a good three-dimensional model of bone(s) of the treated patients. Existing methods that convert the Computer Tomography (CT) images into the polygonal three-dimensional models are time-consuming and inefficient. Therefore, we propose a predictive model that allows quick creation of three-dimensional (3D) surface model of a particular bone by measuring the relevant parameters from an X-ray or CT image.In this paper, we present the process of creating a predictive geometrical model using the case of proximal end of fibula as an example. The predictive model is built by defining the referential geometric entities that correspond to anatomical features, based on which appropriate points, axes, planes and curves are created. Using the method of linear and nonlinear regression with four different parameters, which can be measured from X-ray images or anterior-posterior projection of fibula at CT scans, the equations for X, Y and Z coordinates of the selected 168 points are obtained and their predictive values are calculated. These values are used for creating 3D surface model with the aim of two different methods: using loft function and converting these coordinates into point cloud. These models were compared and verified through analysis of deviations and distances between initial model and predictive models. The resulting 3D model has satisfactory accuracy, and the process of its building is much shorter.