Russian Journal of Biomechanics

Sagittal balance of the spine characterizes its physiological alignment by muscular forces in the most effective way. Optimal spinal-pelvic relationships form a biomechanically efficient and optimal sagittal profile of the spine, which reduces energy consumption for an equilibrium state maintaining and also decrease the risk of degenerative damage to the intervertebral discs. Sagittal balance is described using the main angular parameters: pelvic incidence, lumbar lordosis, pelvic tilt and sacral slope. To form optimal spinal-pelvic relationships during surgical treatment surgeons measure the actual balance parameters of the patient and use empirical formulas to calculate their theoretical values at preoperative planning stage. To calculate the optimal parameters of the sagittal balance of a particular patient, various scientific groups have developed a number of empirical dependencies. However, there is no consensus in the scientific community on what specific formulas to use when planning treatment. This paper attempts to generalize the data available in the scientific literature on the parameters of the sagittal balance and to develop new generalizing regression dependencies that allow one to link the parameters of the sagittal balance. For this purpose, the source data used for constructing such dependencies were collected from the literature. The results of the sagittal balance measurement of Saratov State Medical University patients were also used in this study. We selected the initial numerical data linking the main parameters of the sagittal balance from the literature. The data was digitized and processed using statistics methods. Regression dependencies were obtained that allow calculating lumbar lordosis, pelvic tilt, and sacral slope through the pelvic incidence of a particular patient. Generalizing dependences make it possible to systematize the clinical experience accumulated in the literature and were used in the development of the world's first system for preoperative planning of surgical treatment of the consequences and diseases of the spine-pelvic complex with biomechanical support of the doctor's decision.

The purpose of our study was to evaluate the predictive value of a new complex parameter rheological coefficient of red blood, which is a calculated index of the following values: number of RBC, MCV, RDW, MCH. In this work, we investigated the rheology of the blood in a healthy population in villages of Sachkhere region, Georgia (Sareki, Sairkhe, Chorvila). To determine the validity of the rheological coefficient of red blood with another parameter that studies the rheological status of blood, we examined a group of patients with arterial hypertension. The rheological status was investigated using the "Georgian Technique" and compared with the rheological coefficient of red blood, i.e. we have determined the equivalence of these methods. The use of the rheological coefficient of red blood will increase the information content and expand the field of blood rheology research while reducing costs for the patient, hospital, and healthcare.

In this paper, we discuss a possibility of evaluating a part of the energy cost for maintaining a vertical posture by a person. We use the stabilometric data (center of pressure (CoP) postural sway measurements) only. The application of an inverted pendulum model for calculating the components of the mechanical work of particular groups of leg muscles is described. We use integral of the modulus of the power of total torques developed by the antagonists. For the sagittal direction, the mechanical work of muscles of the ankle is make an estimate mainly, and for the frontal direction - of the pelvic muscles. The possibility of using approximate estimates of energy indicators for the slow components of human movement is discussed. To analyze the correlations of various indicators, the results of postural stability tests were used. During these tests the subjects stood with their eyes open in an upright posture. Moreover, in several tests, they were presented with various visual illusions. It was causing a change in postural characteristics and, accordingly, stabilometric parameters. The correlations between the introduced energetical indicators and indicators traditionally used in stabilometry are analyzed. The next indicators: CoP trajectory range of oscillations along the frontal and sagittal, the average CoP velocity and its projection on the frontal and sagittal axes, as well as an indicator called the "total energy density of statokinesiogram" and its components for the frontal and sagittal directions - were considered. A correlation between the used indicator of mechanical work and the stabilogram range was developed. It is shown that the change in a part of the energy corresponding to an indicator called the «total energy density of statokinesiogram" is small and, apparently, does not adequately characterize the change in mechanical energy.

The mechanical tests of saphenous veins on static tension have been carried out. Significant factors affecting the strength of the vein are the varicose vein transformation and thickness of the vascular wall. The ultimate strength of samples without varicose transformation is significantly (0.9 MPа) higher than that of veins with varicose transformation and the increasing in the thickness walls by 1 mm decreases this parameter by 3.9 MPa. At the same time, the minimum values of ultimate strength the for both groups was more than 0.4 MPa (3000 mm Hg), which allow us to use the veins for prosthesis of the arterial bed. As a plastic material, it is advisable to use varicose veins with a vascular wall thickness (double) less than 0.35 mm, for unchanged veins this parameter should not exceed 0.58 mm. Also, our results indicate the absence of differences in the deformation and strength characteristics between the samples of the saphenous veins when stored in solutions of different chemical composition.