Nikola Vitković

Reverse modeling and solid free-form fabrication of sternum implant

The paper presents a case where an implant for a part of the sternum (with costal cartilages) affected by cancer was created and implanted by using the specific reverse modeling method and solid free-form fabrication. The method provides surgeons with a fast and reliable tool for tissue engineering and implantation and therefore improves the quality of life for patients. Digital images of healthy sternum samples were used to develop a reverse modeling algorithm that semi-automatically generates a necessary and sufficient simplification of the tissue geometry to be fabricated in an inexpensive and applicable manner. In this particular case, the redesign of the missing part of the sternum in CAD software took three designer-hours. At the same time, the suitable simplification of the geometry affects the fabrication of simpler and less expensive casting molds. Furthermore, the core of the developed algorithm for the reverse modeling of sternum can be applied in the reverse modeling improvement of other tile (or plate-like) bones.

A case of using the Semantic Interoperability Framework for custom orthopedic implants manufacturing

Abstract The efficiency and effectiveness of the daily practice in orthopedic surgery depend on the availability, interoperability and unique access to a wide set of information, related to the patient’s medical record and diagnosis, domain knowledge and available resources and staff. The most important of the tangible resources, needed for the therapeutic or preventive actions are orthopedic implants. In some cases, the implants may be highly complex and customized products, which need to be manufactured (assembled) on basis of the above information in a shortest possible timeframe. In this paper, the case of the custom orthopedic implants manufacturing is described from the perspective of the collaborative enterprising, with special consideration of the interoperability issues of the involved enterprise collaboration. It is shown how the previously developed Semantic Interoperability Framework can be used to improve the efficiency of the manufacturing and other relevant processes.

The Parametric Model of the Human Mandible Coronoid Process Created by Method of Anatomical Features.

Geometrically accurate and anatomically correct 3D models of the human bones are of great importance for medical research and practice in orthopedics and surgery. These geometrical models can be created by the use of techniques which can be based on input geometrical data acquired from volumetric methods of scanning (e.g., Computed Tomography (CT)) or on the 2D images (e.g., X-ray). Geometrical models of human bones created in such way can be applied for education of medical practitioners, preoperative planning, etc. In cases when geometrical data about the human bone is incomplete (e.g., fractures), it may be necessary to create its complete geometrical model. The possible solution for this problem is the application of parametric models. The geometry of these models can be changed and adapted to the specific patient based on the values of parameters acquired from medical images (e.g., X-ray). In this paper, Method of Anatomical Features (MAF) which enables creation of geometrically precise and anatomically accurate geometrical models of the human bones is implemented for the creation of the parametric model of the Human Mandible Coronoid Process (HMCP). The obtained results about geometrical accuracy of the model are quite satisfactory, as it is stated by the medical practitioners and confirmed in the literature.

DESIGN STUDY OF ANATOMICALLY SHAPED LATTICED SCAFFOLDS FOR THE BONE TISSUE RECOVERY

The current major scaffold design concepts for bone tissue recovery are characterized by labyrinthine design. Their main shortcomings are low level of permeability for new growing tissue, poor design adaptability in regard to particular anatomy and required biomechanical conditions during recovery, as well as very demanding post processing after free form fabrication. In contrast to the most of the existing solutions, latticed scaffold design does not try to imitate the trabecular structure and rejects the labyrinthine concept. It is characterized by simple 3D latticed support structure, which provides a high level of permeability for the new growing tissue cells, and in the same time a proper level of bio-adhesiveness. In addition, its design is easy to manage in order to make it follow the particular anatomical shape and at the same time provide the required elastic properties and structural strength. The paper presents a part of design concept proving process, which is related to stress analysis of the anatomically shaped lattice scaffold design. The aim of the analysis was to identify functional relation between design parameters and elastic properties of the scaffold. The established relations are crucial for getting optimal values of elastic properties of scaffold that are required in a specific trauma-fixation case. The design study shown in the paper was done for the case of lattice scaffold anatomically shaped to the upper part of proximal diaphyseal trauma of rabbit tibia. Design parameters which were altered within the design study were lattice’s struts cross-sectional area, density of the struts and angle of the struts intersection. The analysis showed that structural flexibility of latticelike scaffold may easily be changed through modification of three selected design parameters. In this way, it is confirmed that the proposed type of scaffold has an important capability to adapt its elastic properties to the required values, while being able to keep its great permeability and geometrical consistency to the particular anatomy of trauma region.

Analysis of semantic features in free-form objects reconstruction

Abstract One of the biggest challenges associated with design and digital reconstruction of free forms comes from uniqueness and unrepeatability of these shapes. During digital reconstruction of these forms, the designer has to choose the right set of geometric features and then compose them in a way that will enable the most accurate reconstruction of the geometry. While doing this, the designer primarily relies on personal experience gained through work with free-form objects of similar geometry. In our opinion, the analysis of free-form objects geometry should rely upon semantic interpretation of their geometric and other features, and the greatest challenge of automation of digital reconstruction and free-form object design in general is closely related to automation of semantic interpretation of geometric and other free-form object features. In this paper, a case of chest bone implant digital reconstruction is presented, where a new semantic model called the active semantic model was used for modeling the meaning of geometric elements, that is, the semantic features of a free-form object. The active semantic model and its analogy-based reasoning algorithms have shown themselves as applicable for the automation of semantic interpretation of the unique, unrepeatable, and unpredictable forms of chest bone. Moreover, this semantic model showed the potential to help automate selecting and composing of geometric features for efficient digital reconstruction of the geometry of free forms.

MATERIAL CHARACTERIZATION ISSUES IN FEA OF LONG BONES

One of the main issues that arise during preparation of models for subject specific finite element analysis (FEA) of long bones is the accuracy of material characterization. This paper tends to identify the most common sources of material characterization errors, which are sometimes also interconnected with bone geometry reconstruction errors, in order to help in creation of more accurate finite element models of long bones. Reconstruction of patients bone geometry is usually based on medical images obtained by means of computational tomography (CT). Material characterization is performed either by segmentation of the model to characteristic zones that are assigned typical averaged material properties, or by local material mapping, based on bone density values estimated from CT numbers. Some of the main factors that influence material characterization accuracy are the choice of material model, the approach to material properties averaging, x-ray tube parameters, scanner calibration, relations between CT image gray values and bone density and relations between bone density and elastic properties of the bone. The paper brings a comparison of numerical results obtained from a number of subject-specific analyses of human femur, in which the approaches to material modeling were varied. Material modeling was performed using either geometry segmentation with material properties averaging or local material mapping. The results of the analyses were examined and mutually compared, and the influence of material characterization errors to analyses results was identified and explained.

IT Support for University Spin-Off Companies

Using information technologies can contribute significantly to the successful start of a company and its later progress. However, successful implementation is connected to certain expenses, which smaller companies (such as university spin-off companies) usually cannot afford. The analysis of existing approaches to implementation of IT and information systems will be performed in this chapter, along with the study of applicability of their use in university spin-off companies. As a conclusion, we will propose the best way to choose and use IT systems.

Software Framework for the Creation and Application of Personalized Bone and Plate Implant Geometrical Models

Computer-Assisted Orthopaedic Surgery (CAOS) defines a set of techniques that use computers and other devices for planning, guiding, and performing surgical interventions. The important components of CAOS are accurate geometrical models of human bones and plate implants, which can be used in preoperational planning or for surgical guiding during an intervention. Software framework which is introduced in this study is based on the Model-View-Controller (MVC) architectural pattern, and it uses 3D models of bones and plate implants developed by the application of the Method of Anatomical Features (MAF). The presented framework may be used for preoperative planning processes and for the production of personalized plate implants. The main idea of the research was to develop a novel integrated software framework which will provide improved personalized healthcare to the patient, and at the same time, provide the surgeon with more control over the patients treatment and recovery.

Customized anatomically adjusted plate for fixation of mandible internal fractures

Mandible internal fractures are a common injury because of the mandibles lack of structural support. For the treatment of such injuries various fixation elements are used. In order to improve quality of the orthodontists interventions anatomically correct and geometrically accurate customized implants are necessary. In this paper an example of accurate geometrical model of the customized plate implant for the fixation of mandible fracture is presented. For the creation of such model new method has been developed. This method is based on reverse engineering techniques applied on the CT scan of the specific patient mandible. With the application of this method it is possible to create geometrical model of the customized plate implant which geometry and topology conforms to the shape of the mandible of the specific patient. The side of the implant, which is in contact with a periosteum outer layer of the mandible, is fully aligned with the shape of the mandible outer surface near the fracture. The obtained model(s) can be used for production of plate implants, and/or for simulation of orthodontist interventions.