Romuald Będziński

FT-Raman spectroscopic study of human skin subjected to uniaxial stress.

Fourier Transform Raman Spectroscopy was used to investigate the molecular changes of structural proteins in human skin subjected to strain. In the Raman spectrum of unstrained skin, bands assigned mainly to collagen and elastin were observed at 1658 cm(-1) (amide I), 1271 and 1255 cm(-1) (amide III), and 935 and 817 cm(-1) (C-C stretching modes of the protein backbone). Moreover, bands characteristic for amino acids were observed at 1336 cm(-1) (desmosine), 1004 cm(-1) (phenylalanine), 919 and 856 cm(-1) (proline), and 877 cm(-1) (hydroxyproline). Positions and intensities of the listed Raman bands were analysed as a function of applied strain. A clear correlation between Raman wavenumbers and the level of mechanical stress was established. Wavenumbers of the analysed bands changed gradually with increasing strain. Distinct responses, depending on the sample cutting direction, i.e. longitudinal or perpendicular to the Langers lines, were noticed. It was concluded that elastin and non-helical domains of collagen are initially involved in the load transfer and triple helices of collagen are gradually joining this process. It was proved that Raman spectroscopy give insight into skin deformation micromechanics.

Comparative biomechanical study of cervical spine stabilisation by cage alone, cage with plate, or plate-cage: a porcine model

Purpose. To compare stability and subsidence associated with 3 types of cervical spine stabilisation. Methods. The C3 to C4 vertebrae of 28 Polish pigs were used. Pigs with intact vertebrae (group 1) underwent standard anterior cervical discectomy (group 2), followed by stabilisation using a cage alone (group 3), a cage with plate (group 4), or a plate-cage (group 5). Cervical spine stability and subsidence were compared in all 5 groups. Results. Stability was significantly increased after stabilisation by a cage with plate or a plate-cage, but not by a cage alone. The difference between stabilisation by a cage with plate and a plate-cage was not significant. Subsidence was maximal after the cage-alone stabilisation (3.1 mm), being 1.6 mm after the cage-with-plate and plate-cage stabilisations. Conclusion. Additional plating as a supplement to anterior interbody cervical cage stabilisation significantly improves segmental stability and subsidence.

Biomechanical effect of rapid mucoperiosteal palatal tissue expansion with the use of osmotic expanders

The comparative study was performed to investigate the biomechanical properties (maximum tangential stiffness, maximum tangential modulus and tensile strength) of expanded mucoperiosteal palatal tissue after rapid expansion regimen correlated with histological findings. Rabbit palatal model was used to correlate the non-operated control group, sham-operated control (subperiosteal tissue dissection) groups and 24- and 48-hour tissue expansion groups. There was no observed damage of tissue collagen network in both tissue expansion groups analyzed immediately after expansion, and biomechanical profile was not significantly different from the profile of control groups. However, rapid tissue expansion activates remodeling of mucoperiosteal tissue structure that revealed significant changes in mechanical properties during the 4-week follow-up. The 24-hour expansion induced transient increase of resilience observed 2 weeks after surgery in comparison to the control groups. As a result of maturation of newly created collagen fibers and mucoperiosteum rebuilding, there were no significant differences between any of the analyzed tensile parameters 4 weeks after the 24-hour expansion. Increased and elongated inflammatory response and connective matrix synthesis observed during healing of 48-hour expanded tissue led to a significant decrease of tensile strength value in comparison to the control groups. Even though 4 weeks after surgery, the resilience of 48-hour expanded tissue was similar to the control groups, tissue healing was not completed and limited scar formation might considerably change the final biomechanical tissue profile. These findings provide new information about tensile properties to rapid mucoperiosteal palatal tissue expansion with the use of osmotic expanders for cleft palate repair by tissue augmentation.

Experimental and constitutive modeling approaches for a study of biomechanical properties of human coronary arteries

The study concerns the determination of mechanical properties of human coronary arterial walls with both experimental and constitutive modeling approaches. The research material was harvested from 18 patients (range 50-84 years). On the basis of hospital records and visual observation, each tissue sample was classified according to the stage (0, I, II, III) of atherosclerosis development (SAD). Then, strip samples considered as a membrane with the shape of rectangular parallelepiped were preconditioned and subjected to uniaxial tensile tests in longitudinal (n=27) and circumferential (n=4) direction. With experimental data obtained, the stress-strain characteristics were prepared. Furthermore, tensile strengths and related strains, stiffness coefficients and tangent modules of elasticity were computed. For a constitutive model of passive mechanical behavior of coronary arteries, values of material parameters were computed. The studies led to the following conclusions. Most importantly, the atherosclerotic changes affect all the mechanical properties of arterial walls. A progress of arteriosclerosis contributes to an increase of vascular stiffness. The highest values of the stiffness coefficients are obtained for the tissues in the advanced stage of the disease. We were also able to observe that gradual calcification, progression of atherosclerosis and degradation of collagen in the tissue caused a decrease of tensile strengths and related strains. Finally, a comparison made for the tissues with the advanced SAD showed that the tensile strengths and strains were much higher in the case of the samples with the circumferential orientation rather than those with the longitudinal one.

Comparative studies of cervical spine anterior stabilization systems - Finite element analysis

BACKGROUND The object of the study was to assess the impact of one-level stabilization of the cervical spine for both anterior static and dynamic plates. Segments C2-C6 of the cervical spine, were investigated, from which was determined the stress and strain fields in the region of implantation and adjacent motion segments. The purpose was the comparison of changes that affect the individual stabilizers. METHODS For testing we used finite element analysis. The cervical spine model takes into account local spondylodesis. The study includes both an intact anatomical model and a model with implant stabilization. FINDINGS The analysis covered the model loaded with a moment of force for 1 Nm in the sagittal plane during movement. We compared both the modeled response of the whole fragment C2-C6 and the response of individual motion segments. The largest limitation of range of motion occurred after implantation with static plates. The study also showed that the introduction of the one-level stabilization resulted in an increase in stress in intervertebral disc endplates of adjacent segments. INTERPRETATION The results indicate that the increase in stress caused by stiffening may result in disorders in remodeling of bone structures. The use of dynamic plates showed improved continuity strains in the tested spine, thereby causing remodeling most similar to the physiological state and reducing the stresses in adjacent segments.

Numerical Analysis of the Risk of Neck Injuries Caused By IED Explosion under the Vehicle in Military Environments

Abstract As a result of an explosion under a military vehicle, the risk of threat to life and health of the crew increases. Examination of this event in terms of the security of soldiers comes down to a complex analysis of the mutual interaction of the body of a soldier, seating and structural elements of the vehicle. As a result, shock wave impacts can cause tremor resulting from the construction of the vehicle and acceleration of the passengers body. This study attempts to analyze the impact of an explosion of an improvised explosive device (IED) under the military vehicle with the risk of cervical spine injuries of soldiers. The analysis was carried out using numerical methods in the LS-DYNA program and was carried out taking into account the variable displacement values and acceleration recorded during the\ explosion. The study used a model of the body of a soldier in the form of a Hybrid III 50th Male Dummy.

Biomechanical characteristics of the jump down of healthy subjects and patients with knee injuries

PURPOSE The aim of this study is to investigate the drop jump performance of male patients who underwent ACLR and a control group using combined data acquisition system. METHODS A total of 28 male subjects aged 20 to 26 were studied: 22 did not show and were not diagnosed with any knee joint dysfunction (the control group) and six men who underwent ACLR of the left limb (group of patients). The control group was age, height and body mass matched. A data acquisition setup consisting of three independent modules including force platforms, position analysis system and electromyography was used. Subjects were jumping down from 0.1, 0.2, and 0.3 m step heights. The acquired signals were used to determine the ground reaction force, muscular activity, mass centre position, velocity and acceleration. RESULTS Statistically significant differences were found between the groups (t-test, p < 0.05) in the maximum vertical ground reaction force in the left limb for 0.2 and 0.3 m step heights. Differences in the muscle activity between the groups were found to be statistically significant (t-test, p < 0.05) before the jump, during the landing phase, and after the jump for selected muscle groups and step heights. CONCLUSION Combing the three independent measurement systems provided new information on drop jump biomechanics. The distribution of loads in different muscles was not uniform across the groups. Patients allocated more energy to control their motion and seemed to protect their operated limb by shifting the bodyweight to the healthy limb.

Biomechanical characteristics of the porcine denticulate ligament in different vertebral levels of the cervical spine—Preliminary results of an experimental study

BACKGROUND Few studies exist on the mechanical properties of denticulate ligaments and none report the variation in these properties at different levels of the spine. The aim of this study was to perform an experimental determination of load-extension and stress-strain characteristics of the denticulate ligament and to establish if their properties change at different vertebral levels of the cervical spine. METHOD The study was carried out on a total of 98 porcine denticulate ligament samples dissected from seven fresh porcine cervical spinal cord specimens. All of the samples were subjected to an uniaxial tensile test at a speed of 2mm/min, during which the load-extension characteristics were registered. RESULTS The analysis revealed a decrease of the failure force in the caudal orientation indicated by significant differences between the C1 (1.04±0.41N) and C7 (0.55±0.12N) vertebral levels (P=0.037). The average ultimate force that broke the denticulate ligaments was 0.88N. The mean value of Young׳s modulus was 2.06MPa with a minimum of 1.31MPa for C7 and maximum of 2.46MPa for C5. CONCLUSIONS The values of the denticulate ligament failure force in samples from different cervical vertebrae levels differ significantly. The presented data should be taken into consideration during numerical modelling of the human cervical spinal cord.

Biomechanical Basis of Tissue–Implant Interactions

Tissue-implant interactions were analysed by investigations of bone adaptation processes, especially in the region surrounding the implant. In such cases all factors stimulating bone negative remodelling should be taken in consideration. Because of that, a three-step analysis of implant alignment to the surrounding tissues was carried out. Basic parameters of the bone-implant interaction were estimated (on the macro level: stiffness characteristics, shear strains distribution, and bone tissue density distribution; on the micro level: trabecular structures development, trabecular microcracks distribution, and bone cells strain distribution). Estimation of each parameter was carried out by development of numerical tools which enabled control of bone tissue changes caused by changes in the implant design. All steps of the analysis were carried out using FE models and own simulation procedures.

Mechanical properties and dynamics of degradation of polylactide matrix composites with calcium and sodium alginate fibers

In the present article, new polylactide/alginate fibers composites were investigated. Composite pre-pregs were made by solution casting method. The aim of the study was to define physico-mechanical properties of developed materials. The scope of the studies included: examining the static mechanical properties, properties of the surface and their changes during degradation. Moreover, intensity of the release of degradation products to the environment and a change of the mass of examined samples were analyzed. Obtained results were evaluated taking into account possibility to use prepared composited as materials for vascular implants.