Biomechanics in Medicine, Sport and Biology

Polylactic acid (PLA) is a biodegradable non-toxic, biocompatible polymer used as a popular filament material in biomedical applications with the advance of 3D printing technologies. PLA is considered a suitable implant material due to its contribution to bone regeneration. In this study, the use of PLA in Total Hip Arthroplasty (THA) as a liner material was assessed. In this regard, the PLA liner with different material combinations in THA was examined to provide evidence for its potential. The hip implant prototypewas drawn using a computer-aided design tool then transferred into a commercial finite element analysis (FEA) software. The prototypesconsisted of assemblies of PLA with titanium, chrome cobalt, stainless steels, dense NiTi shape-alloys, and Alumina-Zirconia. Simulations were run under static loading conditions. To evaluate and compare the results for the optimum design; factor of safety, total deformation and von Mises stress analysis were used. The results show that Co-Cr implemented implants produce the highest factor of safety. When Al-Zi combined with PLA, it produced least deformation and reasonable von- Mises stress values. PLA might perform best when used with Al-Zi. As a next step, experimental pre-clinical tests are planned to assess the clinical potential.

The paper deals with the problem of determining of parameters describing the degree of trabecular bone structure anisotropy. The Mean Intercept Length (MIL), the most commonly used characteristics of anisotropy in trabecular bone, was taken as a gold standard method. As an alternative description, an approach was proposed in which the degree of anisotropy was defined as the ratio of the apparent modulus determined by mFE in two orthogonal directions. For the analyses, an important issue was to determine the direction of occurrence of the maximum value of the apparent modulus. The paper also presents the procedure of calibrating the numerical model in terms of the correct definition of the boundary conditions for analyses carried out with trabecular tissue samples cut at rotated coordinate system.

Total Hip Arthroplasty (THA) is one of the best advancements in healthcare. THA is required when the hip joint causes immobility and pain. The designed hip implants vary in geometry with different geometrical parameters. The geometry plays an important role in the mechanical behavior of the hip implant. In this study, the optimum selection of hip implant under static loading was evaluated using Finite Element Modeling (FEM). Hip implants with three different stem cross-sections including. (a) elliptic, (b) oval, and (c) trapezoidal were designed using a commercial Computer-Aided Design (CAD) software package. The FEM analysis was carried out via ANSYS R2019 to assess the key mechanical parameters of the implants such as stress distribution and deformation. The results were evaluated for the best stress and strain values. The optimum design had equivalent stress (von Misses) of 258,1 MPa, equivalent strain of 0.004, with total deformation of 0.24 mm and frictional stress of 0.362 MPa producing best values for trapezoidal cross-sectioned design. The findings of this study provided an insight into the selection of appropriate hip implant design with certain geometric design parameters to produce optimum results in clinical applications.

In this article, results of numerical finite element method (FEM) simulations of a Boston orthopedic brace in the Ansys environment are presented. A reverse engineering methodology based on digitization by means of a three-dimensional (3D) optical scanner was employed to develop the geometric model. The force flow lines characterizing the brace and indicating the general working method of the orthosis’s structure were determined using the FEM model. Identification of the main areas of the orthosis, carrying loads correcting the spine and of the positions of sites exerting little effort, from the perspective of their participation in the orthosis’s essential therapeutic application, was carried out. Methods for mechanical optimization of the brace’s design can be proposed based on the results obtained. As the conducted analysis is universal in character, it can be adapted to other types of orthopedic braces.

The presented study deals with a familiar situation when unsecured objects are transported in a vehicle. Unsecured objects have a character of objects dedicated to daily usage – work purposes or personal purposes. That generally means laptops, cell phones, tablets, drinks in a glass bottle, objects for sports, and others. Objects of interest are considered stiff/rigid with an insignificant portion of deformability.

The study focuses on the interaction between unsecured objects placed inside a vehicle and vehicle occupants – if a traffic accident happens. If an unsecured object is randomly placed inside the vehicle's inner structure and the vehicle crashes into the barrier, the unsecured objects act like projectiles. These projectiles may, in some cases, interact with occupants' bodies. The interaction may cause, in specific cases, a severe occupant injury. Regarding the human body, the critical part taken for the study purposes is a human head – respectively rear part of a human head with a theoretically insignificant skin thickness. The blunt injury potential (when an unsecured object interacts with a human head) is calculated through Head Injury Criterion (HIC) and Blunt Criterion (BC). Blunt Criterion plays in the presented study a significant role because it serves as a HIC comparison and verification, and the inputs to Blunt Criterion must be carefully selected. If not, the correlation between Head Injury Criterion and Blunt Criterion is not adequately justified.The presented case study shows the selection of the proper and improper values for the Blunt Criterion computations and the influence of the selected values on obtained Blunt Criterion results.

This study aimed to analyze the possibility of using spherical contact pairs to model the articular surfaces of the joints of the wrist. To do so, a three-dimensional surface model of the bones in the wrist was created based on medical scans from computer tomography. Twenty-two pairs of surfaces, which represented the contact areas, were selected and cut out of the model. After that, these pairs were imported into custom software in Python, which allowed for numerical sphere fitting using optimization. The obtained results were then analyzed in terms of the validity of the obtained contact pairs, whether they formed actual ball-and-socket joints and based on fit quality. To verify the results obtained from the first model, a second set of meshes was obtained. The obtained results showed that for most of the joints in the wrist, the spherical approximation might be a viable choice. In some of the cases, the returned radii of the spheres were unusually large, which could mean that different contact pairs, such as the sphere-plane type might be more accurate.

Reconstructive therapy is essential in functionality restoration of the tissues impaired by congenital disorders, degenerative diseases and trauma that needs authentic cells for transplantation and tissue engineering. Petri dish and Cell Culture Flasks produce the cells which properties were changed by the contacts between the cells and the walls of the vessel. A bioreactor for tissue engineering applications should: (i) facilitate uniform cell distribution; (ii) provide and maintain the physiological requirements of the cell (e.g., nutrients, oxygen, growth factors); (iii) increase mass transport by diffusion and convection using mixing systems of culture medium; (iv) expose the cells to vital physical stimuli; and (v) enable reproducibility, control, monitoring and automation. Besides, bioreactors should present a simple reliable design preventing possible stagnation and allowing an easy access to the engineered tissue if any problem arises in the reactor during the operational period. In this paper the state-of-the-art review on different types of the reactors existed in the market, and their benefits is presented. The review is mostly concentrated on the fluid dynamics aspects of 3D dynamic cell culture technologies.

The index finger is a complex structure in the human body, which contains multiple joints. It is used for precise interaction with the environment. In the available studies, the joints of the finger are usually replaced with simple constraints, such as revolute or spherical joints. The main aim of this research was to assess whether the contact areas in the three joints of the finger could be replaced with simple spherical contact pairs. This was motivated by the fact that such contact pairs would allow for more accurate contact analysis than the simplified constraints, while still being computationally inexpensive. The research was performed using two computer tomography datasets, which were transformed into surface meshes of the bones. Parts of the bones, which corresponded to the contact areas in the joints, were selected and imported into Python. Then, sphere fitting was performed in a custom script, which also allowed for visualization of the obtained contact pairs – obtained from the fitted spheres. The pairs were then analyzed. The results showed that it might be possible to replace the contact areas in the joints of the index finger with simple spherical contact pairs. Moreover, in two of the joints, better results were obtained when using two contact pairs – medial and lateral – instead of one for the whole area.

The minimum-time competitive run is reconsidered in the paper. The problem is formulated and solved in optimal control (calculus of variations). A non-classical method of Miele is applied – the method of extremization of line integrals by Green’s theorem. This method gives necessary and sufficient conditions of optimality. Two models of the energy conversions in competitor’s body are considered: the model of Keller and the model of Bonnans and Aftalion. It is shown that the optimal race may be broken into three phases: acceleration, cruise (along so-called singular arc), and final slowing down. The fundamental finding is that the optimal cruising velocity is constant for Keller’s model but it decreases for Bonnans and Aftalion’s model.

The article presents the problem of the mechanical response of nerve roots under stretching conditions. Research into the functioning of the nervous system shows a relation between deformation, blood flow characteristics, and nerve root impulse transmission. These studies show that vascular hypofusion of peripheral nerves occurs at a deformation of 15%. It is also known that impulse conduction disturbances occur at 6% strains. This calculation shows that one of the causes of diseases of the nervous system may be excessive deformation of its structures. One such disease is radiculopathy. Understanding the mechanical response of tissues exposed to damaging conditions requires computations from complex constitutive models that cannot be solved analytically. Therefore, the properties of the tissue material are investigated using numerical approximation methods. For this purpose, it is necessary to experimentally study the properties of the material that allow to determine the parameters of the numerical models used. The aim of the research was to determine the material properties of nerve roots. The analysis was carried out in order to obtain data that would simulate the conditions of the development of nerve root diseases. Modelling was performed using the Finite Element Method (FEM). Mechanical properties were determined on the basis of uniaxial stretching of the nerve roots of the rabbit’s lumbar spine on a testing machine. The tests showed that the rabbit’s nerve root strength is 0.9 ± 0.53 MPa, the relative deformation is 12.73 ± 4.03%, and the Young’s modulus is 2.53 ± 1.00 MPa. The results show the range of strength and stiffness values for various species of animals and humans. The conducted research has shown that the sample preparation procedure has an important influence on the obtained values.

Double-J ureteral stents (DJ stents) are commonly used in urology. The most troublesome difficulty in their application is stent encrustation, stent breakage, and recurrent urinary tract infections. This work aimed was to determine the causes of a double-J stent complication.

The analysis of DJ stents included microscopic analysis, mechanical strength testing, and surface roughness measurements. The analysis was performed on the brand new ureteral stents and ureteral stents implanted after the ureterorenoscopic-lithotripsy (URSL) to treat calcium oxalate stone. Performed analysis of the polyurethane DJ stents concentrated on elaborating the influence of ureteral stent diameter (1.00; 1.33; 1.66 mm) on the affinity to stent encrustation and/or breakage.

The comparison of DJ stents with different diameters confirmed that the risk of encrustation increases with the lower diameter of the ureteral stent. Remaining post-URSL kidney stone fragments deposited on the surface of the DJ stents formed a multilayer structure creating a risk of obstruction or blockage of ureteral stents and block the urine flow. Additionally, a decrease in mechanical strength of the DJ stent related to the implantation time was determined. DJ stent implantation caused an increase in surface roughness.

The performed analysis indicates the need for further exploration of the biomaterials used in DJ stents and modification of their surfaces. This may allow to eliminate the phenomenon of encrustation of urinary stone fragments and NaCl crystals on the surface of implanted stents.

Purpose: The methods of thermal imaging in biomechanics and medicine are still not fully standardised, in contrary to other popular methods of muscle activity examination. This this makes it difficult to compare test results performed in different laboratories or even undermines credibility of some of the results.

Methods: The proposed standardisation procedure is based on the International Association of Certified Thermographers, American Academy of Thermology, European Association of Thermology, scientific publications and authors experience. The most restricted recommendations are chosen, described and discussed.

Results: The standardisation procedure of infra-red imaging in biomechanics is presented and discussed. Volunteer preparation, laboratory conditions, and tips how to make a thermal image are described. The state of the art is presented and chosen aspects of thermal imaging pointed out.

Conclusions: The presented method allows to create repeatable conditions and to minimise the influence of factors that can change the temperature readings. As a result, when using the proposed standardisation, higher repeatability and precision of measurements are obtained.

Background: The aim of this work is to answer the question if a body tattoo can influence thermographic examination and if the results for a new and old tattoo are different. This work is also a continuation of an earlier study devoted to this problem.

Methods: The study was conducted on one volunteer with a tattoo made in a professional tattoo parlour, on the upper part of his chest 16 months and 28 months after making a tattoo. To record a skin temperature distribution, an infrared camera was used.

Results: It is shown that a tattoo may have an influence on a local skin temperature distribution. The main applicable conclusion is that during any kind of thermographic examination, the examiner should expect that the tattoo can locally change temperature readings.