International Journal for Numerical Methods in Biomedical Engineering最新文献

Pulsatile blood flow has the potential to improve microcirculation perfusion and increase the oxygen transfer rate of the oxygenator. However, the specific effects of pulsatile blood flow parameters on the oxygen transfer rate remain unclear. A cross-scale simulation model for the oxygenator is established to investigate the relationship between the oxygen transfer rate of the oxygenator and the pulsatile blood flow parameters. This model comprises a macroscopic model for the oxygenator and a microscopic model for the hollow fiber membrane within the oxygenator. The macroscopic model is employed to calculate the oxygen transfer rate of the oxygenator under various pulsatile blood flow parameters, and a back propagation (BP) neural network is trained to extend the calculation result. The microscopic model for the hollow fiber membrane is employed to elucidate the mechanisms responsible for variations in the oxygen transfer rate. The simulation results demonstrate that at a blood flow rate of 1 L/min, the oxygen transfer rate is minimally affected by blood flow pulsation parameters. While under 2 L/min to 5 L/min, compared to steady blood flow, the oxygen transfer rate can be increased by 3% to 6% when pulsatile blood flow with a pulsation frequency below 0.5 Hz and a pulsation amplitude exceeding 80% is used. However, as the pulsatile frequency increases or the amplitude decreases, the oxygen transfer rate may approach or even fall below the levels achieved under steady-state blood flow conditions.

Platelet plug formation is a critical physiological response to vascular injury, serving as a cornerstone of primary hemostasis. Understanding and simulating this process are essential for advancing patient-specific treatments and interventions. However, achieving a balance between model accuracy and computational efficiency, in particular, for patient-specific scenarios, remains a challenge. In this work, we present a continuum-based approach for simulating platelet plug formation using adaptive mesh refinement, providing a novel solution in this field that enables both accuracy and computational feasibility. Indeed, it integrates a stabilized finite element method within the Variational Multiscale framework to model blood flow dynamics, treated as a non-Newtonian fluid, along with the transport of biochemical species such as platelets and agonists. The platelet plug is represented by an extra stress term in the Navier–Stokes equation, capturing its influence on local blood flow dynamics as a rigid body. A key feature is related to anisotropic mesh adaptation, enabling high-resolution representation of the evolving platelet plug boundary while drastically reducing computational cost. We validate the model against two-dimensional benchmarks under varying shear rates and apply it to a 3D scenario, demonstrating its scalability and precision in simulating thrombosis under complex hemodynamic conditions. The results highlight the model's unique capability to facilitate accurate and efficient patient-specific simulations, offering a transformative tool for advancing personalized medicine.

The purpose of this study was to propose a multiobjective shape optimization approach using the MOPSO algorithm for the femoral stems with the aim of increasing the long-term survivorship of hip implants. The Taperloc Complete femoral stem was selected and its reference geometry was defined with 67 variables. 10 new stem shapes were produced as the swarm members by randomly changing the values of the variables. The values of the stress shielding, initial relative micro-motion, and bone-implant interface stress for each stem shape were calculated as the objectives by the finite element analysis and the position of each swarm member was updated iteratively. The geometry that caused a 37% and 45% decrease in the interface stress and stress shielding, respectively, and a 65% increase in the initial micro-motion compared to the Taperloc Complete stem was selected as the optimized shape. It was shown that thinning the femoral stems without changing their length reduced the induced stress shielding and initial micro-motion and increased the interface stress, whereas shortening the femoral stems reduced the stress shielding and interface stress and increased the initial micro-motion. The proposed approach may be used for the shape optimization of commercial femoral stems to increase their lifetime.

Long-term performance-based study to comprehend the biomechanics of Ti-6Al-4V, PEEK and CFR-PEEK implant materials in fusing a lumbar spine is not available in literature. The present study investigates the performance of these implant materials in fusing an L4–L5 segment by executing a strain energy density-based bone remodelling theory. The FE models of intact and implanted lumbar spines were reconstructed from computed tomography scan images and simulated for 500 N compressive load and a combination of 150 N preload and 10 Nm moment. The models attained equilibrium state when the apparent bone density change became less than 0.005 g cm⁻³ between two consecutive iterations. The implanted models' range of motion (ROM) has been reduced by 73%–85% for Ti-6Al-4V, 64%–78% for PEEK and 69%–81% for CFR-PEEK implanted models. All models exhibit a substantial rise in bone density (30%) in the implant-bone interface region and cancellous bone. However, the CFR-PEEK implanted model exhibited a bone density loss of only 0%–0.3%, compared to the Ti-6Al-4V implanted model (0.3%–6.7%) and the PEEK model (1.5%–30%). The findings indicate that CFR-PEEK material may be a better implant material than PEEK and Ti-6Al-4V while considering bone density distributions and equivalent strains from immediate post-operative to equilibrium conditions.

A mesoscopic fluid–structure interaction (FSI) model focusing on a small region of interest (ROI) in the left coronary artery was developed using COMSOL Multiphysics. This model was on the basis of a previously developed patient-specific coronary artery macroscopic FSI model. With element size comparable to that of endothelial cells, the spatial resolution of the mesoscopic model was significantly improved. Blood flow-induced shear stress and derivatives, vascular wall von Mises stress, and tensile strain (radial and circumferential) in normal and stenosed (50% and 71% occlusion) coronary artery ROIs were calculated, and the results were compared between the current mesoscopic model and the previously developed macroscopic model. Significant differences were observed in shear stress and circumferential strain in the 50% stenosis models. The mesoscopic stenosis model-derived shear stress and tensile strain were applied to human coronary artery endothelial cells concurrently using a shearing-stretching device, and endothelial cell responses (cell morphology and cell surface ICAM-1 expression) were measured. The results demonstrated that the difference in shear stress–tensile strain conditions calculated from the mesoscopic FSI model and the previously developed macroscopic model had a significant impact on endothelial cell responses, suggesting that large-scale FSI models may not be sufficient to characterize local biomechanical conditions at the cellular level.

This study investigates an alternative surgical approach for repairing meniscal root tears, a common knee injury that can significantly impact joint stability and function. Traditional repair methods often face challenges such as high rates of retear and persistent pain. To address these limitations, this research utilizes finite element analysis (FEA) to compare the biomechanical performance of an alternative technique against established surgical procedures. FEA models were carefully constructed to accurately represent the complex anatomy of the knee joint, including the medial meniscus, cartilage, ligaments, and surrounding bone structures. These models were then subjected to various loading conditions that simulated physiological activities such as walking, running, and squatting to assess the stress and strain experienced by the repaired tissue under realistic conditions. The results of the FEA simulations demonstrated a significant reduction in stress and strain on the repaired medial meniscus root when the alternative technique was employed compared to traditional methods. This reduction in biomechanical load is crucial for promoting tissue healing and minimizing the risk of retear. By reducing excessive stress on the repair site, the alternative surgical technique may enhance long-term patient outcomes, potentially improving knee function, reducing pain, and decreasing the likelihood of further surgical interventions such as meniscectomy or knee prosthesis replacement. In conclusion, this study provides strong evidence for the potential benefits of the alternative surgical technique in repairing meniscal root tears. The findings suggest that this approach may offer a promising alternative to traditional methods by optimizing biomechanical stability and promoting more favorable healing conditions. Further clinical studies are warranted to validate these findings and translate these promising results into improved patient care.