Vol 24, No 4 (2020)

Articles
ESTIMATION OF THE ELASTIC CHARACTERISTICS OF THE EYEBALL FROM THE RESPONSE OF THE ENUCLEATED EYE TO THE INTRODUCTION OF GIVEN VOLUMES OF LIQUID
Moiseeva I.N., Stein A.A., Lyubimov G.A.

Abstract

Mathematical modelling of the deformation of the eyeball under the action of internal pressure is performed. The modelling is carried out within the framework of the general approach developed by the authors, which represents the eyeball as a set of a deformable two-dimensional surface (cornea) and a zero-dimensional element that responds with a change in volume to changes in intraocular pressure (scleral region). The calculation results are compared with the experimental data presented in the literature, which are obtained on the enucleated human eyes. It is concluded that the experimentally observed nonlinearity of the dependence of the intraocular volume on pressure is determined by the nonlinearity of the elastic behavior of the cornea, while the scleral region in the studied pressure range is deformed almost linearly. The values of the constants present in the model (corneal and scleral stiffnesses and a parameter that determines the nonlinearity of elastic corneal deformation) are estimated. The values of the elastic moduli turned out to be close to the estimates previously obtained by the authors on the basis of measurements performed on the living eye. The value of the nonlinearity parameter of the cornea, determined from measurements on the whole enucleated eye, turned out to be close to the values estimated by the authors on the basis of data from experiments with an isolated cornea, but slightly lower on average. The individual values of all elastic parameters for specific examined eyes differ markedly from each other.
Russian Journal of Biomechanics. 2020;24(4):412-429
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DEVELOPMENT OF A NONINVASIVE METHOD FOR DETERMINING BLOOD VISCOSITY
Rzayev A.G., Rasulov S.R., Rzayev E.A.

Abstract

The aim of the study is to develop a new method for noninvasive determination of dynamic viscosity. In the developed method, the methods of mathematical modelling and the laws of rheology, mechanics, biomechanics and human physiology were used. It has been shown that an increase in blood viscosity leads to functional failure of various organs and tissues, disorders of the coronary and cerebral circulation. As a result of the analysis, it was revealed that blood can be considered as a colloidal suspension in which particles of erythrocytes and platelets are suspended, and the viscosity of such a colloidal system in microcirculation does not obey the Newtonian law. At the same time, the main factors that significantly affect blood viscosity include: blood pressure of hematocrit, platelet count, absolute amount of fibrinogen proteins and microglobulins, and lipoprotein concentration. A mathematical model has been obtained for determining the viscosity of the colloidal dispersed blood system, considering the concentration of the dispersed phase (blood cells) and the structure formation of blood; a model for determining the thickness of the boundary layer of blood corpuscles adsorbed on the inner surface of blood vessels is proposed and the mechanism of blood structure formation associated with the surface charges of erythrocytes and platelets is shown.
Russian Journal of Biomechanics. 2020;24(4):430-438
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MATHEMATICAL MODELLING OF EPITHELIAL TISSUE DYNAMICS
Krasnyakov I.V., Bratsun D.A., Pismen L.M.

Abstract

The rapid development of computer technologies and high-performance computing systems has led to the possibility to simulate directly the biomechanical properties of cell tissue. This simulation reproduces both the averaged dynamics of the tissue considered as a continuous medium and the behavior of each cell. In this paper, we propose a mathematical model of epithelial tissue, which is considered to be two-dimensional. In this case, the shape of the basement membrane, on which the epithelium lies, generally, may have a topology that is more complex than the plane. The model is discrete since the tissue consists of cells, each of which evolves according to its scenario. Each cell is a polygon, the number of vertices and shape of which can change during evolution. The model includes two important processes that mimic the properties of real cells. The first one is mitotic cell division, the algorithm of which is written in such a way that the new cell inherits all the properties of the mother cell. Another important process is cell intercalation, which makes the epithelium a mobile elastic medium adapting under the influence of internal and external influences. For each vertex of the cell, we write an equation of motion based on the elastic potential energy. Since the cell resists deviation from the average volume and excessive deformation of the shape, the epithelium as a whole tends to find a state corresponding to a minimum of potential energy. Even though the cellular tissue allows internal movement of elements, it is, generally, a highly dissipative medium. Thus, tissue biomechanics should obey rather Aristotelian dynamics. The model allows a simple generalization to the case of feedback between the biomechanical and chemical properties of the medium (for example, the processes of gene regulation in cells leading to chemoelasticity), the introduction of several competing species of cells (for example, the occurrence of a cancerous tumor), three-dimensional cell tissue, and so on. Specific examples of modelling the dynamic behavior of epithelial tissue are given.
Russian Journal of Biomechanics. 2020;24(4):439-454
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GROUND REACTION FORCES DURING STAIR CLIMBING IN TRANSFEMORAL AMPUTATION - A CASE STUDY
Gawłowska A., Zagrodny B.

Abstract

Conducting a gait analysis allows us to make an accurate diagnosis to document the progress of rehabilitation, as well as properly adapt the prosthesis to the patient. This study focuses on examinating the differences between a choosen healthy person (OZ) and a choosen person after an amputation (OPA) with enucleation in the knee joint in case of climbing stairs (ascent and descent). Two male volunteers of similar age (20-22 years) and height (180-185 cm) participated in the study. Biomechanical analysis was carried out using three prosthetic sets differing in knee joints (1. Blatchford Mercury, 2. Guardian, 3. Ottobock 3R80) and prosthetic foot (1. Össur Vari-Flex XC Rotate, 2. SACH, 3. Blatchford Elite 2). The staircase consisted of four steps (height 170mm, width 320mm). During the experiment, an optoelectronic motion capture system and force plate were used. Obtained results showed limited efficiency of ascending and descending stairs by OPA, compared to OZ. The most important difference between a healthy person and an amputee is their gait pattern, step-over-step and step-by-step gait, respectively. The value of the vertical component of the ground reaction force when climbing stairs is similar for both subjects. The analyzed parameters differ depending on the prosthetic set used by OPA. During the descent, the OPA can implement the step-over-step pattern, but only using the prosthesis set I (everyday use). Then, the forces acting on the sound limb during the stance phase are much higher than for OZ, which creates the possibility of overloading the given limb. The conducted biomechanical analysis draws attention to the importance of proper selection of the prosthesis for the patient.
Russian Journal of Biomechanics. 2020;24(4):455-468
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STUDY OF THE DENTAL ZIRCONIUM IMPLANT SURFACE IN A NANO-SCALE USING AN ATOMIC-FORCE MICROSCOPE
Dzhalalova M.V., Stepanov A.G.

Abstract

The influence of various surface treatments of zirconium implants on the adhesion strength in the connection “individual milled transdental implant - cement - hard tooth tissues” was investigated. As analogs of such implants, we used pins made of zirconium dioxide, individually made for prepared previously extracted teeth, in combination with the most effective Fuji-1 and Multilink-N cements. To assess the quality of the formed "cleanliness" of the surface, the experiments were carried out in two stages. At the first stage, the samples were processed by a sandblasting machine under a pressure of 2 atmospheres by aluminum oxide powder with a grain size of 50, 100 and 250 μm. The treatment was carried out once in one direction, longitudinally to the axis of the implant. At the second stage, the same samples were processed again in the same mode, but in two directions. The processed samples were studied in a probe nanolaboratory (Troitsk, Russia) using an atomic force microscope (AFM). Roughness parameters were measured in nanometers on each sample from three images of a scanning probe microscope (SPM). Analysis of the SPM images revealed that the roughness of the samples is higher when processed with larger grains. The results of the study showed that a single sandblasting by zirconium dioxide is quite enough to improve the adhesive properties of the implants both to the fixing cements and to the patient's bone tissue.
Russian Journal of Biomechanics. 2020;24(4):469-474
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STUDY OF MOTION AMPLITUDES IN LARGE JOINTS OF UPPER AND LOWER LIMBS AND SPINE JOINTS WHEN USING INDUSTRIAL EXOSKELETONS
Geregey A.M., Bondarchuk E.V., Malahova I.S., Efimov A.R., Tah V.H., Sotin A.V.

Abstract

One of the world trends of Industry 4.0 is the introduction of exoskeletal technologies into production processes. Manufacturers of industrial exoskeletons designed to reduce the negative impact of the work process on the human locomotive apparatus provide for the redistribution of the external load on the human body by means of various technical solutions. However, there is currently no uniform methodology for assessing the operational safety of exoskeletons. A significant biomechanical factor contributing to the safety of industrial exoskeletons as promising means of personal protection of the locomotor apparatus, is possibility to work without significant restrictions on the volume of movements. In this connection, the development of a methodology for objective quantification of the influence of structural and mass dimensions of industrial exoskeletons on the biomechanics of human movements is a topical task. This article presents the results of the measurements of the amplitude of movements in the large joints and joints of the spine, when performing the tests for flexion-extension, adduction-abduction and lateroflexion. The testing of volunteers was carried out on the clinical base of NII MT. The tests were performed both without the use of industrial exoskeletons (Group I) and with their application (Group II). The influence on the biomechanical parameters of volunteer movements by the structural characteristics of the industrial exoskeleton “Exochair” and two different models of the industrial exoskeleton “Exoatlant” was investigated. Parameters of movements of segments of the human body were measured with the help of inertial measuring sensors of the software and hardware complex “Biomechanika Trust-M”. Quantitative indicators have been identified which show the limitations of movements caused by the operation of different models of industrial exoskeletons. Thus, the use of the exoskeleton “Exochair” in deep seating limits the flexion in the hip joint by 67.1 %, in the knee joint by 56.1 %, in the lumbar thoracic spine by 61.9 %, and practically does not affect the flexion in the shoulder joint. The first model of the exoskeleton “Exoatlant” limits the amplitude of movements in the hip joint by 41.2 % at flexion and by 74.5 % at extension. At the same time, the second model limits the abduction of the shoulder joint by 20.5 %, and in the lumbar thoracic spine limits forward flexion by 17.3 %, rearward extension by 50.6 %, bending to the right by 46.4 %, and bending to the left by 40.3 %.
Russian Journal of Biomechanics. 2020;24(4):475-490
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MATHEMATICAL MODELLING OF BIOMECHANICAL BEHAVIOUR OF THE REMOVABLE DENTAL PROSTHESIS BASIS UNDER THE CHARACTERISTIC CHEWING LOADS
Arutyunov S.D., Grachev D.I., Bagdasaryan G.G., Nikitin V.N., Maksimova N.V., Nikitin A.D.

Abstract

In this work, we consider the issue of mathematical modelling of the biomechanical response of the removable lamellar prosthesis basis to external loading due to chewing load, from the moment of biting of food in the area of incisors to the final formation of a food dot in the area of molars. For this purpose and uniform presentation of the calculation results, for upper and lower lamellar prosthesis, at complete absence of teeth, the associated physically-based boundary conditions are selected. Modelling of the mucous membrane is carried out within the framework of the concept of an elastic foundation. However, for each of the considered prosthesis bases, its own morphologically substantiated features of the deformation behavior of the mucosa are introduced. In the case of the upper prosthesis basis, such a feature is the presence of a torus region; for the case of the lower prosthesis basis - the key role has the alveolar process. In the work, the stress-strain state is simulated in the bases of the upper and lower prostheses with symmetric and asymmetric loading on the main blocks of teeth: block 1 - incisors, block 2 - canine, block 3 - premolars, block 4 - molars. The value of the external load for each of the blocks is calculated based on the values of the characteristic muscular effort of the maxillofacial apparatus. The issues of setting individual blocks of teeth, the effect of their displacement relative to the recommended line of installation and slopes on the stress-strain state of the prosthesis base are investigated. A qualitative and quantitative comparison of the maximum stress fields and their spatial distribution is carried out for various configurations of installing tooth blocks and types of loading. The work shows that asymmetrical loading is the most dangerous from the point of view of the structural integrity of the prosthesis basis. Potential destruction of the denture basis can occur due to regular loading of the first two blocks of teeth. The factors that contribute to a reduction in the service life of the removable prosthesis basis under typical chewing loads have been identified.
Russian Journal of Biomechanics. 2020;24(4):491-504
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APPLICATION OF THE LONG FIBULAR TENDON IN ANTERIOR CRUCIATE LIGAMENT PLASTIC SURGERY: BIOMECHANICAL PROPERTIES OF THE GRAFT, CORRELATION RELATIONSHIPS
Lychagin A.V., Aliev R.L., Bogatov V.B., Churbanov S.N., Timashev P.S., Muzychenkov A.V., Garkavi A.V., Petrov P.I., Lipina M.M.

Abstract

Surgery of the anterior cruciate ligament with its injuries is currently one of the most frequent in sports traumatology. There are many methods for its implementation, but one of the most frequent questions is the choice of a transplant to replace it. The graft must withstand loads comparable to an intact ligament. It is necessary to choose the most suitable human tissue for this purpose. This article discusses the biomechanical characteristics of the long tibial tendon as a graft for the anterior cruciate ligament. Our results allowed us to evaluate the mechanical properties of the graft obtained from the tendon of the long fibular muscle, to compare the data obtained with the available literature data describing the mechanical properties of the grafts used, and to show that the graft chosen for evaluation in this study is not inferior in its properties to those already used. The presence of a correlation between the graft diameter and the gender of patients suggests that further detailed statistical analysis will determine the possibility of accurate prediction of the graft diameter for high-quality preoperative planning.
Russian Journal of Biomechanics. 2020;24(4):505-512
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ERGONOMIC ASSESSMENT OF SPORT SKIES BASED ON ANALYSIS OF ATHLET’S HEMODYNAMICS AT LOADING TEST USING TONOMETRY AND ELECTROCARDIOGRAPHY
Shilko S.V., Kuzminsky Y.G., Bondarenko K.K., Bogdanova N.S.

Abstract

Occlusive tonometry and resting electrocardiography are widely used in medicine to diagnose and monitor the state of the cardiovascular system. In recent years, software and hardware implementations of these methods for fitness and sports training have been developed thanks to the advent of portable and mobile gadgets. The paper presents the results of an analysis of the athlete’s hemodynamics in real time according to the data of tonometry and electrocardiography performed synchronously during the three-stage load-speed testing “rest - load - recovery”. It is shown that application of these diagnostic methods, one-dimensional biomechanical modelling of hemodynamics and statistical dependences obtained experimentally allow us to monitor very important and informative indicators of energy efficiency of human movement (oxygen consumption, dynamics of oxygen debt, shared distribution of aerobic and anaerobic energy sources). In fitness, sport training and competition conditions such monitoring has been realized only with the use of complex and expensive devices. In this regard, it is proposed to use the mobile software and hardware complex developed by the authors and biomechanical criteria (heart rate before and after exercise, oxygen consumption, oxygen debt) characterizing the energy consumption of an athlete, including the quality rating of sports equipment, in particular, cross-country skis. The selection of skis adequate bionically is based on a statistical analysis of the results of load-speed testing of a group of athletes.
Russian Journal of Biomechanics. 2020;24(4):513-527
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