Department of Biomechanics – 13253

List of persons

• prof. Ing. Jiří Burša, Ph.D. – head of department
• prof. Ing. Přemysl Janíček, DrSc.
• doc. Ing. Zdeněk Florian, CSc.
• doc. Ing. Vladimír Fuis, Ph.D.
• Ing. Petr Marcián, Ph.D.
• Ing. Pavel Švancara, Ph.D.
• Ing. Petr Hájek, Ph.D.
• Ing. Jiří Vaverka

Biomechanics is an extremely wide scientific branch connecting methods of theoretical and practical mechanics that exploit the knowledge from other scientific branches which deal with living organisms such as, medicine, biology, biophysics, etc. Biomechanics is explained by the means of several examples from different fields at the Institute of Solid Mechanics, Mechatronics and Biomechanics, specifically in the cardiovascular system, biomechanics of musculoskeletal system and bioacoustics.

The members of the research group have been collaborating with important medical and research institutions in the Czech Rep. (St. Anne’s University Hospital, University Hospital Brno, Trauma Hospital of Brno, University Hospital Olomouc, General University Hospital in Prague, Institute of Thermomechanics AS CR, Palacký University Olomouc) and prestigious foreign research institutions (Royal Institute of Technology Stockholm, Nagoya University, Vrije Universiteit Amsterdam, Tokyo Medical & Dental University, Tampere University of Technology, University of Stuttgart). They participate in conferences and seminars in the Czech Republic and abroad. The results are published in renowned international journals.

Biomechanics of cardiovascular system

The basic research in this area focuses on analysing the artery structure and the influence on their mechanical behaviour. Physicians have detailed knowledge of the components that form the artery walls. However, the directional arrangement of collagen fibres in arteries, which determines their mechanical properties, is not their concern. We combine biaxial mechanical tests of tissues for a better description of such properties (see fig. 1) using the image analysis of their structure obtained from a microscope. Our greatest achievement so far has been discovering the structure of the aorta collagen fibres in pigs (see fig. 2), on which we collaborated with our colleagues from St. Anne’s University Hospital. Currently, we are working on determining the collagen fibre properties using polarized microscopy, which is also crucial for mechanical response of the vessel tissue (see fig. 3).

Our team’s applied research focuses on the risk of aortic aneurysm burst, which is a serious illness of the human aorta. The goal of this research is to provide physicians with a computational modelling tool capable of distinguishing hazardous aneurysms from the stable ones. Like in the technical applications, we try to accurately calculate the tension in a given aneurism (see fig. 4) and compare it to its strength. Due to a wide range in values, it is necessary to use statistical methods to determine the probability of damage in the aneurism wall. We use medical data such as CT images or patient blood pressure. We succeeded in designing a computational method of damage probability that proved to be the best so far out of all the known procedures. We are currently working on improving this method and validating its function on a larger number of patients. We are collaborating with St. Anne’s University Hospital as well as prof. T. Christian Gasser from the Royal Institute of Technology, Stockholm, an expert in this branch.

Another field of interest is determining the risk of an atheromatic plaque rupture (see fig. 5). Atherosclerosis is by far the most common vessel illness and the atheromatic plaque rupture in a vessel can lead to life threatening conditions such as cardiac arrest or stroke. Therefore, it is vital to know in which plaques the rupture can develop and where it is not likely. Apart from this, we also carry out a research on the influence of electrical activity of the heart (EKG) on the heart chamber contraction (see fig. 6). In this research we collaborate with St. Anne’s University Hospital and Masaryk University.

Contact: prof. Ing. Jiří Burša, Ph.D.

Fig. 1: Pig aorta sample sections for biaxial mechanical tests

Fig. 2: 3D imaging of the distribution of collagen fibres in a pig aorta. Close to the bloodstream (lumen) the fibres are mainly oriented in a circumferential direction (right angle 90°) and towards the outer surface of the artery the preferential orientation disappears, and the fibres are randomly oriented

Fig. 3: Imaging of wavy collagen fibres using polarized microscopy; frequency histogram of fibre parts in individual directions defining their waveform; the influence of the waveform on the deformation-tensional response of the tissue

Fig. 4: First principal stress in the aortal aneurism under the mean patient load (inner side (a), outer side (b)) and with increased blood pressure, which leads to a local overload of the aneurism wall (arrow)

Fig. 5: Stress field in the idealized geometry of the atherosclerotic plaque reveals the hazardous areas

Fig. 6: 3D finite element model of the left heart chamber (on the left), considering its wall layers (in the middle) and the orientation of the contractile muscle fibres (on the right – red lines show the orientation of the muscle fibres in a layer)

Biomechanics of a musculoskeletal system

Biomechanics of a musculoskeletal system is a field, which focuses on the mechanics of the musculoskeletal system and its elements, i.e. bones, cartilage, muscles, ligaments etc., or on the mechanics of the musculoskeletal system with prosthetic or fixation devices. This scientific field has existed at the ISMMB for over 25 years and, currently, our research focuses on the following:

• replacement arthroplasty,
• fracture repair of long bones,
• spinal biomechanics and spinal fixation,
• dental implants,
• craniomaxillofacial implants and fixation devices,
• remodelling of bone tissues.

These areas focuse on specific problems in clinical practice as well as on studies concerned with new findings enriching the theory of musculoskeletal biomechanics. The models of the problems solved have a very high resolution. The bone tissue models are created using the information from the computed tomography (CT), micro CT or pQCT, which help determine the mechanical properties of the bone tissue more accurately. Using the information form these devices we can create the geometry models and materials as well. The high resolution of the models and experience and erudition of the academic workers allows us to solve the problems for a particular patient individually making splints and fixation devices. Modelling and remodelling of the bone tissue is a particular field that builds on the solutions of a number of biomechanical problems.

Kontakt: Ing. Petr Marcián, Ph.D.

Bioacoustics

The research team focuses on computational modelling of human voice production. It concentrates especially on modelling of vocal cord self-oscillation, where the problem is to find the interaction between fluid, structure, and acoustics. Another area of interest is modelling the sound waves spreading through the vocal tract and their emission from the mouth to the area around the head. The models are created in cooperation with doctors based on CT and MRI scans of their patients and on experimental data obtained from partner institutions: Institute of Thermomechanics AS CR and Palacký University Olomouc. These models can be used to analyse the way the pathological changes in the vocal cords tissue influence the oscillation and voice, to make surgery predictions, and assess the behaviour of implants.

Kontakt: Ing. Pavel Švancara, Ph.D.