Russian Journal of Biomechanics

The main goal of preoperative planning for patients with pathologies of the musculoskeletal system is to obtain high-quality anatomical and functional results. The solution to this problem could be achieved through the selection of appropriate implants and technique of their installation, which ensure the stability of the structure and reposition of bone fragments, as well as by recreating the optimal biomechanics of the operated segment. All over the world, modern digital technologies are widely introduced into clinical practice. In traumatology, orthopedics and neurosurgery, preoperative planning systems that implement virtual treatment planning allow performing X-ray morphometric measurements on digital radiographs or computed tomography, as well as placing implant templates and selecting their optimal standard size. Typically, several treatment types can be planned for a particular patient, which are successful in terms of geometric preoperative planning. But not each of the planned types can be optimal in terms of assessing the stress-strain state of the studied segment of the spinal pelvic complex. Biomechanical modelling provides the possibility of virtual modelling of orthopedic operations, including the assessment of segment stability and implant "survival". Therefore, it is proposed to use biomechanical modelling as a tool for preoperative planning. In this regard, at the request and with the financial support of the Advanced Research Fund at Saratov University, for the first time, the development of a Russian medical decision support system in surgery of the spinal pelvic complex is being developed, which provides not only the stage of geometric planning of the operation, but also its biomechanical support, as well as predicting treatment results. The aim of this work was to show that biomechanical modelling makes it possible to choose the optimal type of surgical treatment of diseases and injuries of the spine-pelvic complex, and can also be successfully introduced into preoperative planning and successfully function within the framework of the medical decision support system. The paper presents the results of demonstration experiments, in which the optimal treatment types for degenerative diseases of the spine and hip joint were selected using the system. The results of the experiments were consistent with the established clinical practice and literature data, and a group of experts confirmed their clinical viability. It was shown that, together with geometric planning, biomechanical modelling forms a new method (algorithm) for preoperative planning.

Collateral blood vessels have been statistically linked to a higher probability of repeat stenosis, but these data are not conclusive. Therefore, the aim of this research is to study a possible hydrodynamic pathway for stenosed coronary arteries for two scenarios: in absence of collaterals and in presence of collaterals with different collateral flow indices. For this in this study, we utilised an analytical model and a numerical model for studying this pathway. First, we performed an analytical calculation for the arterial bifurcation with a stenosis and a collateral vessel. Then, we carried out a numerical calculation using an existing numerical model for the same topology. Thus, we obtained the data characterizing the dependence of the wall shear stress on the stenosis degree for various Y-topology cases (without collaterals, and with different collateral flow indices). Then, based on the numerical model, we calculated the dependence of the wall shear stress on the stenosis degree for the physiology-based left coronary artery topology (without collaterals, and with different collateral flow indices). Moreover, to choose the stenosis location to study in the model, we used stent placement frequency statistics, based on data accumulated in clinical practice. As a result, analysis of the obtained data showed that for the structures studied in this work, collateral flow index does not affect the dynamics of restenosis. Thereby, the presence of collateral vessels is unlikely to have an influence on restenosis growth dynamics, and the link is likely purely statistical or follows a different pathway.

According to the latest research, cancer is a complex biosystem that develops in time and space. This means that cancer cells differ from each other in their function in the tumor. They are involved in various interactions with their microenvironment and compete for available nutrients for reproduction and survival. Identifying a specific structural type in the growth of a malignant tumor is one of the main problems today in oncology. The other no less important problem of mathematical modelling in oncology is the heterogeneity of a malignant neoplasm. In this work, we propose a chemomechanical model of the structure formation of small groups of cancer cells of invasive carcinoma of a non-special type. The model suggests that carcinoma is a heterogeneous mass of cells of different phenotypes that perform different functions in the tumor. Each cell is represented by an elastic polygon that changes its shape and size as the tissue develops. Numerical modelling implements various subtypes of invasive carcinoma of a non-special type structure. The patterns are compared with morphological structures previously identified in clinical studies.

It is recognized that Covid-19 is mainly transmitted by airborne droplets. It is especially dangerous to sneeze and cough the patient, when together with a jet of air, moving at a high speed (when sneezing up to 150 km/h), droplets of liquid containing viruses fly out. It is known that even with a loud conversation the patient can release up to 1000 drops in the air with particles of a new type of coronavirus, especially coughing and sneezing carrier of the virus. There is a lack of experimental data to create physical and numerical models describing these processes and calculate the concentration of aerosol particles. The paper proposes an installation to determine the distribution of velocities and deformations in the time of the aerosol cloud that occurs when coughing and sneezing, as well as preliminary results of the first cycle of experiments at this installation. Based on the results, recommendations are made to counter the spread of infection. The purpose of these studies is to determine the direction and speed of the cloud carrying the droplets with the virus, as well as the time of its passage past potential recipients. Based on these data, it will be possible to estimate the received dose of infection and the dependence of this dose on the distance between the source and the potential victim. The study does not claim to be complete, which can be achieved by studying large groups of subjects, but after its completion it can serve as a source material for close to reality digital models of infection transmission. The work also contains preliminary results of the first cycle of experiments at this facility. On the basis of the results obtained, practical recommendations are given to counteract the spread of infection.

Intramedullary osteosynthesis is currently one of the main methods of treating fractures of long tubular bones. There is a large selection of both the fixators themselves and the manufacturers of these implants. The aim of this study was to conduct biomechanical testing of three types of intramedular rods - ChM, BNB (three-bladed), SarNIITO rod and Fixion (Israel) in femoral fractures of types A1, A2, A3 and B1. According to the results of the study of the displacement of fragments in different types of fractures, affecting the “bone-fixator” system with three types of loads (axial, transverse and rotational) - the stability is not the same. The most commonly used cross-blocking rod (or perhaps the entire type of such rods) showed fairly good indicators of the stability of fragments that can lead to the desired result - bone fusion. The use of different types of intramedullary fixators based on a different method of locking in the bone (transversely inserted screws, by expanding in the bone marrow canal, embedding the blades into the bone from the inside and with a spoke) allows a more rational approach to increasing the stability of a fixed fracture by using their positive sides. So, for a fracture of type A1 and A2, it is better to use Fixion rod. With a transverse bone fracture line (type A3), it is better to give preference to the three-bladed BNB rod, since it holds the transverse and rotational load better, and when exposed to the axial one, the fracture is autodynamized (compression), stimulating regeneration. Fractures of type B2 (comminuted, with a small contact line between the fragments) require the maximum possible stability. For this purpose, Fixion rod is better suited, which is blocked throughout the entire bone marrow canal. But when it is used, it is possible for the fragment to move away from the mother bed when the rod is stabilized by its expansion.