Biomechanics and Modeling in Mechanobiology最新文献

Biomechanical modeling of the human trunk is crucial for understanding spinal mechanics and its role in ergonomics and clinical interventions. Traditional models have been limited by only considering the passive structures of the spine in finite element (FE) models or incorporating active muscular components in multi-body musculoskeletal (MS) models with an oversimplified spine. To address those limitations, we developed a subject-specific coupled FE-MS model of the trunk and explored its applications in ergonomics and surgical interventions. A parametric detailed FE model was constructed, integrated with a muscle architecture, and individualized based on existing datasets. Our comprehensive validation encompassed tissue-level responses, segment-level mechanics, and whole-spine behavior across multiple subjects and loading conditions, demonstrating satisfactory performance in ergonomics (i.e., wearing exoskeleton) and clinical interventions (nucleotomy and spinal fusion). The model accurately predicted tissue-level stresses (in uni- and biaxial loading), whole-spine motion (i.e., moment rotation response was in agreement with in vitro measurements), intradiscal pressures (RMSE = 0.12 MPa; R² = 0.72), and muscle activities (matching EMG trends across 19 subjects during forward flexion). Wearing an exoskeleton reduced intradiscal pressures (1.9 vs. 2.2 MPa at L4–L5) and peak von Mises stresses in the annulus fibrosus (2.2 vs. 2.9 MPa) during forward flexion. Spinal fusion (at L4–L5) increased the intradiscal pressure in the upper adjacent disc (1.72 MPa vs. 1.58 MPa), but nucleotomy had a minimal effect on the intact intradiscal pressures. Nucleotomy substantially affected the load transfer at the same level by increasing facet contact loads and annulus radial strains. Unlike conventional MS models with simplified spine, and in contrast to passive models (without active components), this model provides crucial outputs such as strain/stress fields in discs/facets (essential for a comprehensive risk analysis). This integrated approach enables more accurate surgical planning, workplace safety design, and personalized rehabilitation strategies, helping reduce spine-related injuries by identifying risk factors and optimizing interventions for individual patients.

There is growing motivation to exploit computational biomechanical modeling of the heart as a predictive tool to support clinical diagnoses and therapies. Existing patient-specific cardiac models often rely on data collected under highly standardized conditions in hospitals. However, disease progression and therapy responses often depend on stressors, encountered in daily life, that cannot be captured in a traditional clinical setting. To achieve clinical translation, existing modeling frameworks must be refined and extended to include such influences. The “digital twin” concept, in which models of specific systems are continually updated with new data, is a promising avenue for integrating and interpreting these data streams. However, this endeavor calls for novel approaches to model development and data acquisition and integration. We review modeling approaches addressing specific stressor types (caffeine, exercise, sex-dependent factors, sleep, the environment) to identify knowledge gaps, assess emerging technical challenges, and suggest potential model developments to extend the scope and reach of biomedical cardiac simulations.

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The study is focused on comparative analysis of different concepts for design of scaffolds for bone tissue engineering based on investigation of their local physical–mechanical properties and response to compression load. Three-dimensional additively manufactured lattice scaffolds with various morphological characteristics and mechanical responses are investigated numerically and experimentally and compared to representative volume elements of real random microstructure of trabecular bone. Prototypes of the studied structures are fabricated with polylactide using a fused filament fabrication technique. Numerical analysis of stress–strain state of scaffolds under compressive loading is performed. The effect of changes in structural morphology parameters on the initiation of stress concentrators as well as nucleation and propagation of fracture is studied. Strain fields on samples’ surfaces, captured in the experiments with a micro-digital image correlation technique, are in good agreement with the obtained numerical results. Comparison of the mechanical behaviour and properties of the lattice-scaffold prototypes with those of trabecular bone allows conclusions about selection of their rational morphological structure. Based on the results obtained with the comprehensive analysis, two promising approaches to create scaffolds similar to trabecular bone were identified: models based on a variation of the gyroid surface and ones using Voronoi tessellation with Lloyd's relaxation algorithm.

Thrombotic deposition plays a critical role in the evolution of various vascular pathologies and is a major consideration in the development of cardiovascular devices. Although experimental evidence has shown that shear gradients in blood flow play a critical role in thrombogenesis, the impact of these gradients has not been included in previous computational models of thrombosis. The goal of the present work is to develop a predictive computational model of platelet plug formation that accounts for the role of shear gradients. A 2D computational model of platelet-mediated thrombogenesis was developed using the commercial finite element solver COMSOL Multiphysics 5.6. The model includes platelet transport, activation, adhesion and aggregation induced by both biochemical and mechanical factors. Platelet and agonist transport are described by a coupled set of convection-diffusion–reaction equations. Platelet adhesion and aggregation at the vascular surface are modeled via flux boundary conditions. Thrombus growth and its impact on blood flow are modeled using a moving surface mesh. The model provides the spatiotemporal evolution of a platelet plug in the flow field. After validation against experimental data in the literature, the model was used to predict the location and growth dynamics of platelet plugs in various vascular geometries. The results confirm the importance of considering both mechanical and chemical platelet aggregation and underscore the essential role that shear gradients play in platelet plug formation. The developed model represents a potentially useful tool for thrombogenesis prediction in pathological scenarios and for the optimization of endovascular device design.

Nasal hairs, often overlooked in human respiratory system studies, can be a decisive factor in maintaining respiratory health. Vibrissae can capture a certain range of particle sizes due to their filtering function, while they may also contribute to more breathing resistance. In this study, the role of nasal hairs in particle filtration and pressure drop within the nasal vestibule was investigated using computational fluid dynamics (CFD) simulations. Seven nasal hair specifications were examined in simplified human nasal vestibule models under steady laminar flow conditions at two airflow rates of 10 and 15 L/min. The deposition of microparticles in the simulated geometries was also numerically studied. The simulation results showed that the investigated nasal hairs lead to about a 2–20 Pa increase in the pressure drop, depending on the hair specifications and airflow rates. The associated growth in nasal resistance could potentially influence breathing comfort. Additionally, nasal hair was shown to enhance particle filtration, with the deposition fraction of particles correlating with the projected area of the hairs on a normal plane to the flow direction, which goes up by an increase in the number of hairs or their length. These findings clarify the significance of nasal hairs in the respiratory system and aim to balance the trade-off between improved particle filtration and increased breathing resistance due to nasal hairs. The acquired knowledge can be used in recommendations to different individuals regarding nasal hair trimming based on their health conditions.

Graphical Abstract

When cyclic stretch is applied to a monolayer of cells cultured on an elastic substrate, many types of cells align in the direction perpendicular to the stretch or along the direction of minimal substrate strain. However, the behavior of multilayer cells under cyclic stretch remains unclear. In this study, we cultured MC3T3-E1 osteoblast-like cells at high density to form multilayer cells and subjected them to cyclic stretch with an amplitude of 10% at 1 Hz. We found that the lower layer cells aligned in the direction of the stretch after 12 h, whereas the upper layer cells aligned perpendicular to the direction of stretch after 24 h. The 10% cyclic stretch was transmitted to the upper layer cells as approximately 5% at the onset of the stretch and increased over time, reaching 7% at 12 h when the lower layer cells completed alignment in the direction of stretch. This suggests that sufficient cyclic stretch transmitted to the upper layer led to the alignment of the upper layer cells in the perpendicular direction after 12 h. On the other hand, reducing intracellular tension with Y-27632 caused cells in both upper and lower layers to align in the direction of stretch. In contrast, increasing intracellular tension with calyculin A eliminated significant alignment in both layers. These findings indicate that cell alignment is closely related to intracellular tension and that the alignment of the lower layer cells in the direction of stretch may be due to a decrease in intracellular tension.

Ventilation of the maxillary sinus is essential for regulating pressure, preventing infection and providing mucous to the nasal anatomy. During infection, the pathway between the sinus and the nasal airway (ostia) can become inflamed and restrict ventilation. Surgery is often required to restore airflow. The current surgical standard involves the widening of the ostium. Although this restores fluid flow, it has been linked to post-surgical sequelae. This study examined the effects of pulsating flow and geometric modifications on airflow distribution in a T-junction model analogous to a nasal maxillary ostium. A circular T-junction with variable anterior and posterior radius of curvature ((R_c)) was used to simulate airflow through the nasal maxillary ostium, investigating flow behaviour under oscillatory inlet velocities at frequencies of 30, 45, 60, and 75 Hz. Computational fluid dynamics (CFD) simulations assessed how flow distribution through the nasal cavity and maxillary ostium (represented by the x- and y-branches) is affected by curvature and oscillatory frequency, focusing on implications for respiratory airflow, particle delivery and inhalation toxicology. Results indicated that increasing the anterior (R_c) enhanced airflow into the y-branch (analogous to the maxillary ostium), while posterior curvature had minimal impact. Higher oscillatory frequencies increased reverse flow, which may improve ventilation but could interfere with consistent drug delivery. These insights are valuable for optimising respiratory therapies and inhalation toxicology.

Childbirth is a complex process influenced by physiological, mechanical, and hormonal factors. While natural vaginal delivery is the safest, it is not always feasible due to diverse circumstances. In such cases, assisted delivery techniques, such as vacuum-assisted delivery (VAD), may facilitate vaginal birth. However, this technique can be associated with a higher risk of maternal injuries, potentially resulting in long-term conditions such as pelvic organ prolapse or incontinence. This study investigates the biomechanical impact of VAD on maternal tissues, aiming to reduce these risks. A finite element model was developed to simulate VAD, incorporating maternal musculature, a deformable fetal head, and a vacuum cup. Twelve simulations were conducted, varying contraction durations, resting intervals, and the number of pulls required for fetal extraction. Results revealed that prolonged contraction durations, coupled with extended resting intervals, lead to a reduction in pelvic floor stress. Elevated stress levels were observed when fetal extraction involved two pulls, with an 8.43% decrease in maximum stress from two pulls to four. The peak stress recorded was 0.81 MPa during a 60-second contraction, followed by a 60-second rest period. These findings indicate that longer maneuvers may reduce trauma, as extended pulls allow muscles more time to relax and recover during both contraction and rest phases. Furthermore, an increased number of pulls extends the duration of the maneuver, facilitating fetal rotation and improved adjustment to the birth canal. This study offers crucial insights into the biomechanics of childbirth, providing clinicians with valuable information to enhance maternal outcomes and refine assisted delivery techniques.

Proper functionality of human body relies on several continuous physical processes, many of which are carried out through biological ducts/tubes. For instance, veins, arteries and airways into the human body are natural conduit systems where blood and air are conveyed. Those elastic tubular components are prone to structural instability (buckling) and eventually collapse under critical conditions of net external pressure, resulting in malfunctioning of main physical processes. In the present work, collapsible elastic tubes are studied from a structural mechanics perspective, examining their resistance to collapse under uniform external pressure, emphasizing on the influence of nonlinear material behavior. The problem is approached numerically using nonlinear finite element models, to analyze tubes with diameter-to-thickness ratio ranging from 9 to 30, considering different nonlinear elastic material properties and focusing on the post-buckling phenomenon of “buckling propagation”. It is demonstrated that small softening deviations from linear elastic behavior may cause a localized collapse pattern followed by its propagation along the tube with a pressure lower than the collapse pressure. Results from two-dimensional (ring) and more rigorous three-dimensional (3D) finite element models are obtained in terms of the collapse pressure value and the propagation pressure value, i.e., the minimum pressure required for a localized buckling pattern to propagate, and the two models provide very similar predictions. A simple analytical model is also employed to explain the phenomenon of collapse localization and its subsequent propagation. In addition, special emphasis is given on the correlation between the 3D results and those from ring analysis in terms of the propagation profile and the energy required for the collapse pattern to advance. Finally, comparison with numerical results from tubes made of elastic–plastic material is performed to elucidate some special features of the propagation phenomenon.