International Journal for Numerical Methods in Biomedical Engineering最新文献

Every year, millions of childbirths occur globally, yet the rate of maternal morbidity and mortality remains unacceptably high. This study investigates the biomechanical impact of multiple vaginal deliveries on pelvic floor dysfunction (PFD), a key contributor to maternal morbidity. While the effects of first childbirth on pelvic floor injuries have been widely studied, less is known about the impact of subsequent deliveries. Epidemiological data show that the risk of PFD increases with the number of births, making it crucial to understand how later deliveries exacerbate damage. Using a finite element model, this research simulates the biomechanical effects of first and second vaginal delivery. The model incorporates pelvic floor muscles and a fetal head, considering factors such as muscle recovery and fetal head size. Simulations were run for both first and second deliveries, with varying recovery rates of muscle damage and fetal head sizes (50th and 5th percentiles). Results indicate that muscle damage is most severe at the pubovisceral muscle's origin, which is consistent with previous studies. In second-birth simulations, more muscle damage was observed, particularly when no recovery occurred. Smaller fetal head sizes led to less muscle stretch and accumulated damage. The study supports existing literature linking subsequent childbirths to a higher risk of PFD and highlights the importance of muscle recovery in mitigating damage. It also provides valuable insights into the biomechanics of childbirth, offering a step forward in improving understanding of pelvic floor injuries.

To improve the prediction of renal ostia displacement in biomechanical finite element simulations of the vascular structure deformation during endovascular aneurysm repair (EVAR). An existing finite element model to compute the deformation of the vascular structure due to tools insertion during EVAR, previously validated against clinical data in terms of guidewire position, is confronted in terms of renal ostia displacement to clinical intraoperative data from 16 patients undergoing EVAR and experiencing significant ostia displacement during the procedure (average vertical displacement of 10.38 mm from the preoperative to intraoperative configurations). This yields an update of the mechanical support parametrization. A score quantifies the predictive performance of the existing and updated parametrizations for both the renal displacement and the iliac arteries deformation. The updated model demonstrates a significant improvement in predictive accuracy for renal ostia deviation during EVAR. The axial mean displacement error is improved from 7.41 mm (previous parametrization) to 2.99 mm (updated parametrization). The score shows that this new parametrization improves the predictive performance of the simulation for the renal ostia displacement without compromising the iliac deformations prediction. The updated parametrization significantly enhances the predictive capability for arterial deformations during EVAR. A better prediction of the renal ostia displacement can significantly improve surgical planning and intraoperative guidance.

We conducted an in silico study of blood flow in the brain using two different computational models: fluid–structure interaction (FSI) and conventional rigid wall (CFD). These models were applied to a patient-specific vascular network derived from MRI data. We used a mid-fidelity numerical approach called Transversally Enriched Pipe Element Method (TEPEM) to solve the governing equations. In the FSI model, we coupled the TEPEM strategy with an independent-ring model to account for arterial wall compliance. We compared the FSI and CFD models to understand how arterial wall distensibility affects pressure, flow, and the spatial distribution of flow-related properties. Additionally, we introduced three synthetic anatomical variations in the Circle of Willis to extend the comparison of the FSI and CFD models to these scenarios. Our results suggest that vessel compliance introduces discrepancies up to $��2�$ mmHg in distal cerebral regions and up to $��15�\%�$ in the Wall Shear Stress. Regarding the anatomical variations on the Circle of Willis, the incomplete configuration introduces discrepancies in derived-flow quantities as the Time-Averaged Wall Shear Stress and the Relative Retention Time up to $��20�\%�$.

Existing robot-assisted cracked tooth preparation systems often result in crack extension or even tooth fracture due to inappropriate parameter settings. In order to solve this problem, a thermal–mechanical coupling model was developed to optimize the grinding parameters for a cracked tooth preparation robot. The grinding force model, based on an empirical formula, was established and analyzed. Using this model, the grinding temperature field of the tooth surface under a moving heat source was also determined. The optimal feed speed and rotational speed of the bur were identified through analysis. After verifying the model's accuracy through experiments, the stress intensity factor at the crack tips for various preparation parameters was calculated using the established thermal–mechanical coupling model, enabling the determination of a safe parameter range. Robot-assisted tooth preparation experiments were conducted based on the optimized preparation parameters, which resulted in a 19.32% reduction in normal grinding force and a 56.26% reduction in surface grinding temperature, and consequently a reduction in pulpal thermal damage compared to conventional preparation parameters. Crack extension following tooth preparation was observed by Micro-CT scanning, and the success rate of preventing crack extension was 73.33%, 93.33%, and 86.67% in xoz, yoz, and xoy sections.

In this study, a hygro-elastic finite element framework, along with a strain-energy-density based bone remodeling framework, was developed and used to simulate the swelling of co-polymeric bone anchors to investigate their hygro-mechanical response. To validate the numerical results, free swelling and in vivo experiments were conducted as well. The free swelling experiments were conducted on co-polymeric porous bone anchors (composed of cross-linked poly [methyl methacrylate-co-acrylic acid]) with two ratios of 80/20 and 90/10 to investigate their swelling characteristics in bovine serum, mimicking in vivo conditions. Subsequently, the swelling of bone anchors was simulated embedded in bone regions with different densities. The radial stresses induced in the interface were extracted to examine the mechanical response of the surrounding bone. According to Wolff's law, such mechanical loads can be regarded by bone mechanotransducers as stimuli for remodeling. The bone remodeling framework evaluated the impact of the radial force induced by the swelling of the bone anchor on the surrounding bone. The radial stress induced by the controlled swelling ratio of 90/10 composition resulted in favorable bone densification in the region of interest (approximately between 17.5% and 54% depending on the density of the region). However, the excessive swelling of 80/20 composition caused radial stresses to go beyond the threshold of 31 MPa, causing overload resorption in the interface (especially in high-density regions, where there was total resorption in the interface) and jeopardizing the success of the bone anchor and osteointegration. It was discovered that the swelling ratio plays an important role in bone remodeling, and that it must be controlled within a certain threshold to ensure bone densification and prevent overload resorption. The results of the in vivo sheep study also confirmed these findings.