Biomechanics and Modeling in Mechanobiology最新文献

Rotator cuff muscle (RCM) degeneration, bone morphology, and humeral head subluxation (HHS) are known risk factors for failure of anatomic total shoulder arthroplasty in patients with B-glenoid shoulder osteoarthritis. Yet, the understanding of RCM asymmetry in these patients remains an area of active investigation, including its relation with other risk factors. We therefore aimed to characterize the variability of RCM degeneration in B-glenoids and analyze its covariation with scapular morphology and HHS. First, computed tomography images were used to quantify 3D RCM degeneration, including muscle atrophy and fatty infiltration, in sixty B-glenoids referenced against twenty-five healthy controls. Next, the 3D scapular shape of B-glenoids was quantified using a previously published statistical shape model. Thirdly, 3D HHS was quantified. Using dedicated correlation analyses covariation patterns were modeled between each of these risk factors. Results indicated that RCM degeneration in B-glenoids is primarily characterized by fatty infiltration, without any sign of asymmetric impact on the anterior versus posterior RCM. However, B-glenoids with asymmetric bone loss were found to have more RCM atrophy and fatty infiltration of the infraspinatus. We identified four significant patterns of RCM degeneration and scapular shape, explaining 90.3% of their correlation. The primary mode indicates an association between combined posterior glenoid erosion and coracoid rotation with an increased infraspinatus’ fatty infiltration. Interestingly, this mode was also positively correlated with posterior HHS (r = 0.46, P < 0.01). Identification of such patterns can improve the accuracy of musculoskeletal models in predicting postoperative implant failure risks.

Three-dimensional (3D) hydrogel scaffolds show considerable promise for the regenerative treatment of cartilage and bone defects. Within tissue engineering, these scaffolds can be mechanically stimulated to specifically promote cartilage formation. While in vitro experiments are traditionally used to study the influence of scaffold structure on cell differentiation, in silico studies offer a complementary, cost-effective, and powerful approach. This numerical study employs a transient fluid–structure interaction (FSI) model to modify the structural design of a mechanically stimulated hydrogel scaffold for enhanced cartilage cell differentiation. The study involved two key modification steps applied to scaffolds under 5% compression. In the first step, scaffold porosity was adjusted by altering the number of strands per layer. The scaffold designed with 38% porosity, consisting of 9 strands per layer across 9 layers, improved cartilage differentiation by approximately 15%. The second step focused on scaling the selected scaffold from step 1 by adjusting the number of layers while keeping the porosity constant, aiming to optimize pore dimensions. This led to a slight improvement in cartilage differentiation of about 2.3%. The results indicate that porosity exerts a more significant influence on cell differentiation than pore size in the structured scaffolds investigated. The FSI-based model demonstrates strong potential for analyzing the impact of pore architecture on cell differentiation, although manufacturing challenges of hydrogel scaffolds may limit the practical application of these modification strategies.

The normal healthy aortic valve (AoV) has three leaflets, two of which have outflows to the coronary arteries. Blood flow through the coronary ostia will have an impact on AoV dynamics and the surrounding haemodynamics, leading to differential shear stress distributions at the aortic side of the three leaflets. In addition, aortic root haemodynamics may also be influenced by the non-Newtonian behaviour of blood which is known as a shear-thinning fluid due to the aggregation of red blood cells at low shear rate. However, the combined effect of coronary and non-Newtonian flow on AoV haemodynamics has not been studied in an anatomically realistic setting. In this study, strongly coupled fluid–structure interaction (FSI) analyses were performed on a natural, healthy AoV, with and without accounting for coronary outflows and non-Newtonian properties of blood. Our results showed that the influence of coronary outflow is more pronounced than employing a non-Newtonian model, and their combined effect is non-negligible, particularly on wall shear stress. Incorporating coronary outflow and non-Newtonian properties increased time-averaged wall shear stress (TAWSS) in the aortic sinus by up to 108.45%; it also increased TAWSS on the aortic side of valve leaflets by 41.04%, 44.76%, and 54.91% on the left, right and non-coronary leaflet, respectively. These results highlight the importance of incorporating coronary outflow and non-Newtonian properties when accurate predictions of wall shear stress and its related parameters are critical.

Patient-specific coronary artery biomechanics studies often have limited sample size. The goals of this study were: (1) To develop more patient-specific FSI models to expand current research effort in characterizing hemodynamic and biomechanical conditions within the coronary arteries; (2) to compare some of our model outputs, especially FSI model-generated vFFR values, to those provided by HeartFlow, to evaluate the clinical relevance of our model results. Ten healthy LCA geometries were used to develop patient-specific FSI models using COMSOL Multiphysics. The hemodynamic and biomechanical environment in the arterial wall were assessed, along the proximal, mid, and distal portions of the left anterior descending coronary artery (LAD). The FSI model-calculated vFFR was compared to the matched HeartFlow reports. All FSI models indicated healthy perfusion. There was a good agreement with the HeartFlow calculation in the proximal LAD. The FSI model results indicated that the wall stresses were below the rupture thresholds. However, variations were observed along the arterial length in the von-Mises stress and strains. The FSI models offered improved physiological relevance for LCA simulation by including a large field of view. The biomechanical parameters were minimally related to geometric features, necessitating this procedure. This FSI modeling approach presented a few limitations. More work is needed to address these limitations and improve the physiological relevance of FSI modeling, so it can serve as a non-invasive method to assess the biomechanics of the coronary arteries, to support clinician’s decision making.

Characterizing flow within the right heart (RH) is particularly challenging due to its complex geometries. However, gaining insight into RH fluid dynamics is of extreme diagnostic importance, given the high prevalence of acquired and congenital heart diseases with impaired RH function. In this proof-of-concept study, we propose a pipeline for patient-specific simulations of RH hemodynamics. We reconstruct the geometry and motion of the patient’s right atrium, ventricle, and pulmonary and tricuspid valves, from multi-series cine MRI. For this purpose, we develop a novel and flexible reconstruction procedure that, for the first time, integrates patient-specific tricuspid valve dynamics into a computational model, enhancing the accuracy of our RH blood flow simulations. We apply this approach to study the hemodynamics in both healthy and repaired-ToF RH with severe pulmonary regurgitation, as well as to assess the hemodynamic changes induced by the pulmonary valve replacement intervention. Modeling the entire RH enables us to understand the contribution of the superior and inferior vena cava inflows to the ventricular filling, as well as the impact of the impaired right atrial function on the ventricular diastole. To analyze the turbulent and transitional behavior, we include the large eddy simulation sigma model in our computational framework, which reveals how the contribution of the smallest scales in the dissipation of the turbulent energy changes among health and disease.

Chimney technique is an effective method for guaranteeing left subclavian artery (LSA) revascularization for patients receiving thoracic endovascular aortic repair. However, the complications like endoleak often occur after the chimney technique, and clinical studies have shown that they are closely related to the configuration of the chimney stent graft (SG). In this paper, we simulated the deployment of chimney SG with different angles and thoracic aortic SG, and analyzed the risk of complications according to numerical simulation results. Thoracic aortic SG and chimney SGs with different angles were designed based on patient-specific aortic geometry. The dynamic deployment process of SGs was simulated, followed by computational fluid dynamics (CFD) analysis to evaluate hemodynamic differences. Results indicate that the angle of chimney SG has little influence on the von Mises stress on the vascular wall. The endoleak flow rate at peak systole reached 11.15 ml/s in the 70° configuration, which is 1.80 times that of the 45° configuration. Meanwhile, the flow rate of LSA reached 5.94 ml/s in the 45° configuration, which is 1.21 times that of the 70° configuration. This indicates that the 45° configuration may reduce the risk of endoleak and flow obstruction to LSA. In addition, the relative residence time of 0° or 15° configuration is larger, suggesting a higher risk of thrombosis. This study employs virtual stent deployment and CFD analysis to predict the risk of complications associated with the deployment of chimney stents with different angles, potentially aiding surgeons in selecting the most appropriate surgical plan.

Transjugular intrahepatic portosystemic shunt (TIPS) surgery is commonly employed to treat the portal hypertension (PH), and an appropriate surgical strategy is crucial to balance the surgical outcome and post-TIPS complications. This study numerically explored the effects of six TIPS surgical strategies on the shunt outcome and PV stenosis risk by considering three stent insertion positions with two in-vessel covered lengths from the perspective of the hemodynamics. Sequential CT images of 21 PH subjects were used to reconstruct the six kinds of virtual TIPS surgical models with 6 mm stent and further to compare their five post-TIPS hemodynamic indexes. According to four of the five indexes, it was found that although there was no significant difference between the six surgical strategies, the stent insertion into the main portal vein (MPV) with in-vessel covered length 0 cm was slightly better to reduce the PV pressure, improve the shunt outcome, and potentially decrease the post-TIPS PV stenosis risk. The current findings could be helpful for clinical applications in the aspect of selecting TIPS surgical strategy to treat the PH.

We present a continuum hypothesis-based two-dimensional biomorphoelastic model describing post-burn scar hypertrophy and contraction. The model is based on morphoelasticity for permanent deformations and combined with a chemical-biological model that incorporates cellular densities, collagen density, and the concentration of chemoattractants. We perform a sensitivity analysis for the independent parameters of the model and focus on the effects on the features of the post-burn dermal thickness given a low myofibroblast apoptosis rate. We conclude that the most sensitive parameters are the equilibrium collagen concentration, the signaling molecule secretion rate and the cell force constant, and link these results to stability constraints. Next, we observe a relationship between the simulated contraction and hypertrophy and show the effects for significant variations in the myofibroblast apoptosis rate (high/low). Our ultimate goal is to optimize post-burn treatments, by developing models that predict with a high degree of certainty. We consider the presented model and sensitivity analysis to be a step toward their construction.

This paper presents findings from the SKin Uncertainties Modeling (SKUM) clinical trial aimed at assessing the anisotropic mechanical response of human skin using the annular suction test, employing a numerical method and a commercial device, CutiScan^® CS 100. A cohort of 30 healthy volunteers participated in the trial, undergoing in vivo testing on the left forearm through a multi-axial stretch induced by ring suction. Determination of the anisotropy axis was performed using a numerical method based on model fitting of experimental data obtained from oriented elliptic curves, which resulted from the radial deformation of circles. The study evaluates the reproducibility and variability of measurements through an intra-subject study involving five participants, providing insights into the consistency of results within individuals. Additionally, an inter-subject analysis across all subjects offers a comprehensive understanding of anisotropy variability, elucidating broader population tendencies. Furthermore, the study explores correlations between anisotropy and demographic factors such as sex, age, and skin thickness, shedding light on potential influences on skin biomechanics. The analysis showed significant correlations between skin anisotropy and sex, with males displaying a distinct anisotropy axis orientation compared to females. In contrast, no significant associations were found between anisotropy and age among individuals aged 20–50, or between anisotropy and epidermal thickness.

We introduce an innovative lumped-parameter model of the aortic valve, designed to efficiently simulate the impact of valve dynamics on blood flow. Our reduced model includes the elastic effects associated with the leaflets’ curvature and the stress exchanged with the blood flow. The introduction of a lumped-parameter model based on momentum balance entails an easier calibration of the model parameters: Phenomenological-based models, on the other hand, typically have numerous parameters. This model is coupled to 3D Navier–Stokes equations describing the blood flow, where the moving valve leaflets are immersed in the fluid domain by a resistive method. A stabilized finite element method with a BDF time scheme is adopted for the discretization of the coupled problem, and the computational results show the suitability of the system in representing the leaflet motion, the blood flow in the ascending aorta, and the pressure jump across the leaflets. Both physiological and stenotic configurations are investigated, and we analyze the effects of different treatments for the leaflet velocity on the blood flow.