scholarly journals A Computational Growth Framework for Biological Tissues: Application to Growth of Aortic Root Aneurysm Repaired by the V-shape Surgery

2021 ◽  
Author(s):  
Hai Dong ◽  
Minliang Liu ◽  
Tongran Qin ◽  
Liang Liang ◽  
Bulat Ziganshin ◽  
...  
Keyword(s):  
Aortic Root ◽  
Growth Parameters ◽  
Optimization Procedure ◽  
Biological Tissues ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Aortic Tissue ◽  
The Novel ◽  
Post Surgery

Ascending aortic aneurysms (AsAA) often include the dilatation of sinotubular junction (STJ) which usually leads to aortic insufficiency. The novel surgery of the V-shape resection of the noncoronary sinus, for treatment of AsAA with root ectasia, has been shown to be a simpler procedure compared to traditional surgeries. Our previous study showed that the repaired aortic root aneurysms grew after the surgery. In this study, we developed a novel computational growth framework to model the growth of the aortic root repaired by the V-shape surgery. Specifically, the unified-fiber-distribution (UFD) model was applied to describe the hyperelastic deformation of the aortic tissue. A novel kinematic growth evolution law was proposed based on existing observations that the growth rate is linearly dependent on the wall stress. Moreover, we also obtained patient-specific geometries of the repaired aortic root post-surgery at two follow-up time points (Post1 and Post2) for 5 patients, based on clinical CT images. The novel computational growth framework was implemented into the Abaqus UMAT user subroutine and applied to model the growth of the aortic root from Post1 to Post2. Patient-specific growth parameters were obtained by an optimization procedure. The predicted geometry and stress of the aortic root at Post2 agree well with the in vivo results. The novel computational growth framework and the optimized growth parameters could be applied to predict the growth of repaired aortic root aneurysms for new patients and to optimize repair strategies for AsAA.

scholarly journals Engineering Analysis of Aortic Wall Stress in the Surgery of V-shape Resection of the Noncoronary Sinus

2020 ◽  
Author(s):  
Hai Dong ◽  
Minliang Liu ◽  
Tongran Qin ◽  
Liang Liang ◽  
Bulat Ziganshin ◽  
...  
Keyword(s):  
Aortic Aneurysm ◽  
Stress Field ◽  
Aortic Arch ◽  
Aortic Root ◽  
Wall Stress ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Rupture Risk ◽  
Ascending Aortic Aneurysm ◽  
Post Surgery

AbstractAscending aortic aneurysms often include the sinotubular junction (STJ) and extend into the root portion of the aorta. The novel surgery of the V-shape resection of the noncoronary sinus of the aortic root has been shown to be a simpler procedure, comparing with traditional surgeries such as full aortic root replacement, for patients with moderate ascending aortic aneurysm and aortic root ectasia. This novel surgery could reduce the diameter and cross-sectional area of the aortic root. However, the detailed effect on the stress field and the rupture risk of the aortic root and aneurysm has not been fully investigated. In this study, we performed patient-specific finite element (FE) analysis based on the 3D geometries of the aortic root and ascending aortic aneurysm, reconstructed directly from the clinical computed tomographic (CT) images. By comparing the pre- and post-surgery results, we investigated the influence of the V-shape surgery on the stress field and rupture risk of the aortic root, ascending aortic aneurysm and aortic arch. It was found that the surgery could significantly reduce the wall stress of the aortic root, ascending aortic aneurysm, as well the aortic arch, and hence lower the rupture risk.

Method for Incorporating Three-Dimensional Residual Stresses Into Patient-Specific Simulations of Arteries

2013 ◽  
Author(s):  
David M. Pierce ◽  
Thomas E. Fastl ◽  
Hannah Weisbecker ◽  
Gerhard A. Holzapfel ◽  
Borja Rodriguez-Vila ◽  
...  
Keyword(s):  
Medical Imaging ◽  
Three Dimensional ◽  
Constitutive Models ◽  
Abdominal Aortic Aneurysms ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Abdominal Aortic ◽  
Model Geometry ◽  
Reconstructed Model

Through progress in medical imaging, image analysis and finite element (FE) meshing tools it is now possible to extract patient-specific geometries from medical images of, e.g., abdominal aortic aneurysms (AAAs), and thus to study clinically relevant problems via FE simulations. Medical imaging is most often performed in vivo, and hence the reconstructed model geometry in the problem of interest will represent the in vivo state, e.g., the AAA at physiological blood pressure. However, classical continuum mechanics and FE methods assume that constitutive models and the corresponding simulations start from an unloaded, stress-free reference condition.

scholarly journals Patient-specific resurfacing implant knee surgery in subjects with early osteoarthritis results in medial pivot and lateral femoral rollback during flexion: a retrospective pilot study

2021 ◽  
Author(s):  
Philippe Moewis ◽  
René Kaiser ◽  
Adam Trepczynski ◽  
Christoph von Tycowicz ◽  
Leonie Krahl ◽  
...  
Keyword(s):  
Knee Arthroplasty ◽  
External Rotation ◽  
Knee Kinematics ◽  
Axial Rotation ◽  
Patient Specific ◽  
Post Surgery ◽  
Flexion Extension ◽  
Medial Pivot ◽  
Femoral Rollback

Abstract Purpose Metallic resurfacing implants have been developed for the treatment of early, small, condylar and trochlear osteoarthritis (OA) lesions. They represent an option for patients who do not fulfill the criteria for unicompartmental knee arthroplasty (UKA) or total knee arthroplasty (TKA) or are too old for biological treatment. Although clinical evidence has been collected for different resurfacing types, the in vivo post-operative knee kinematics remain unknown. The present study aims to analyze the knee kinematics in subjects with patient-specific episealer implants. This study hypothesized that patient-specific resurfacing implants would lead to knee kinematics close to healthy knees, resulting in medial pivot and a high degree of femoral rollback during flexion. Methods Retrospective study design. Fluoroscopic analysis during unloaded flexion–extension and loaded lunge was conducted at > 12 months post-surgery in ten episealer knees, and compared to ten healthy knees. Pre- and post-operative clinical data of the episealer knees were collected using a visual analog scale (VAS), the EQ 5d Health, and the Knee Injury and Osteoarthritis Outcome Score (KOOS) questionnaires. Results A consistent medial pivot was observed in both episealer and healthy knees. Non-significant differences were found in the unloaded (p = 0.15) and loaded (p = 0.51) activities. Although lateral rollback was observed in both groups, it was significantly higher for the episealer knees in both the unloaded (p = 0.02) and loaded (p = 0.01) activities. Coupled axial rotation was significantly higher in the unloaded (p = 0.001) but not in the loaded (p = 0.06) activity in the episealer knees. Improved scores were observed at 1-year post-surgery in the episealer subjects for the VAS (p = 0.001), KOOS (p = 0.001) and EQ Health (p = 0.004). Conclusion At 12 month follow-up, a clear physiological knee kinematics pattern of medial pivot, lateral femoral rollback and coupled axial external femoral rotation during flexion was observed in patients treated with an episealer resurfacing procedure. However, higher femoral rollback and axial external rotation in comparison to healthy knees was observed, suggesting possible post-operative muscle weakness and consequent insufficient stabilization at high flexion.

Porohyperelastic Simulation of Abdominal Aortic Aneurysms

2008 ◽  
Author(s):  
Avinash Ayyalasomayajula ◽  
Bruce R. Simon ◽  
Jonathan P. Vande Geest
Keyword(s):  
Wall Stress ◽  
Aortic Aneurysms ◽  
Maximum Diameter ◽  
Patient Specific ◽  
Infrarenal Aorta ◽  
Stress Studies ◽  
Abdominal Aortic ◽  
Peak Wall Stress ◽  
Work Done

Abdominal aortic aneurysm (AAA) is a progressive dilation of the infrarenal aorta and results in a significant alteration in local hemodynamic environment [1]. While an aneurysmal diameter of 5.5cm is typically classified as being of high risk, recent studies have demonstrated that maximum wall stress could be a better indicator of an AAA rupture than maximum diameter [2]. The wall stress is greatly influenced by the blood pressure, aneurysm diameter, shape, wall thickness and the presence of thrombus. The work done by Finol et al. suggested that hemodynamic pressure variations have an insignificant effect on AAA wall stress and that primarily the shape of the aneurysm determines the stress distribution. They noted that for peak wall stress studies the static pressure conditions would suffice as the in vivo conditions. Wang et al have developed an isotropic hyperelastic constitutive model for the intraluminal thrombus (ILT). Such models have been used to study the stress distributions in patient specific AAAs [3, 4].

Fluid Structural Interaction of a Patient Specific Congenital Bicuspid Aortic Valve

2012 ◽  
Author(s):  
V. Govindarajan ◽  
H. S. Udaykumar ◽  
S. Vigmostad ◽  
M. M. Levack ◽  
J. H. Gorman ◽  
...  
Keyword(s):  
Aortic Valve ◽  
Bicuspid Aortic Valve ◽  
Aortic Root ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Aortic Dilatation ◽  
Structural Interaction ◽  
Aortic Pathology ◽  
Specific Geometry ◽  
Opening Phase

Congenital Bicuspid Aortic Valve (BAV) is a valvular anomaly where a patient is born with a valve with two leaflets instead of a normal tri-leaflet valve. It has also been reported that BAVs are prone to progressive calcification and also other complications such as ascending aortic dilatation, dissection and rupture [1]. The geometrical variations with the BAV may be a factor in altering the deformation and stresses on the leaflets resulting in calcification of the leaflets earlier than with normal tri-leaflet aortic valves. Altered flow patterns past BAV into the ascending aorta can also be anticipated. Analysis of flow dynamics during the opening phase, and the resultant fluid forces on the aortic root could improve our understanding of aortic aneurysms and dissections observed in patients with BAV [2]. In this study, the valvular deformation and the flow across a patient-specific BAV and root are simulated using the method of fluid structural interaction analysis. The patient-specific geometry is obtained employing 3D ultrasound images segmented as point cloud data and surfaces are constructed with commercial software GAMBIT using NURBS based connectivity. The opening phase of the valve is simulated under flow with physiological Reynolds number and with realistic material properties for the leaflets and the aortic root. Such an analysis on the dynamics of BAV with patient-specific geometry may be a useful tool in stratifying BAV patients that may be at risk in developing valvular and ascending aortic pathology.

scholarly journals Cornea modelling

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Anna Pandolfi
Keyword(s):  
Clinical Practice ◽  
Clinical Training ◽  
Biological Tissues ◽  
Corneal Biomechanics ◽  
Patient Specific ◽  
Corneal Tissue ◽  
In Vivo Test ◽  
In Vivo Testing ◽  
Living Tissues

Abstract Background Biomechanics introduces numerous technologies to support clinical practice in ophthalmology, with the goal of improving surgical outcomes and to develop new advanced technologies with minimum impact on clinical training. Unfortunately, a few misconceptions on the way that computational methods should be applied to living tissues contributes to a lack of confidence towards computer-based approaches. Methods Corneal biomechanics relies on sound theories of mechanics, including concepts of equilibrium, geometrical measurements, and complex material behaviors. The peculiarities of biological tissues require the consideration of multi-physics, typical of the eye environment, and to adopt customized geometrical models constructed on the basis of advanced optical imaging and in-vivo testing. Results Patient-specific models are able to predict the outcomes of refractive surgery and to exploit the results of in-vivo test to characterize the material properties of the corneal tissue. Conclusions Corneal biomechanics can become an important support to clinical practice, provided that methods are based on the actual multi-physics and use customized geometrical and mechanical models.

scholarly journals MMP-2 Isoforms in Aortic Tissue and Serum of Patients with Ascending Aortic Aneurysms and Aortic Root Aneurysms

PLoS ONE ◽  
2016 ◽  
Vol 11 (11) ◽  
pp. e0164308 ◽  
Author(s):  
Anke Tscheuschler ◽  
Philipp Meffert ◽  
Friedhelm Beyersdorf ◽  
Claudia Heilmann ◽  
Nadja Kocher ◽  
...  
Keyword(s):  
Aortic Root ◽  
Aortic Aneurysms ◽  
Aortic Tissue

Fluid-Solid Interaction Simulation of Flow and Stress Pattern in Thoracoabdominal Aneurysms: A Patient Specific Study

2006 ◽  
Author(s):  
Alessandro Borghi ◽  
Nigel B. Wood ◽  
Raad H. Mohiaddin ◽  
X. Yun Xu
Keyword(s):  
Wall Stress ◽  
Aortic Aneurysms ◽  
Maximum Diameter ◽  
Patient Specific ◽  
Specific Flow ◽  
Hyperelastic Materials ◽  
Abdominal Aortic ◽  
Magnetic Resonance Imaging Mri ◽  
Fluid Solid Interaction

Thoracoabdominal aneurysm (TA) is a pathology that involves the enlargement of the aortic diameter in the inferior descending thoracic aorta and has risk factors including aortic dissection, aortitis or connective tissue disorders (Webb, T. H. and Williams, G. M. 1999). Abnormal flow patterns and stress on the diseased aortic wall are thought to play an important role in the development of this pathology and the internal wall stress has proved to be more reliable as a predictor of rupture than the maximum diameter for abdominal aortic aneurysms (Fillinger, M. F., et al. 2003). In the present study, two patients with TAs of different maximum diameters were scanned using magnetic resonance imaging (MRI) techniques. Realistic models of the aneurysms were reconstructed from the in vivo MRI data acquired from the patients, and subject-specific flow conditions were applied as boundary conditions. The wall and thrombus were modeled as hyperelastic materials and their properties were derived from the literature. Fully coupled fluid-solid interaction simulations were performed for both cases using ADINA 8.2. Results were obtained for both the flow and wall stress patterns within the aneurysms. The results show that the wall stress distribution and its magnitude are strongly dependent on the 3-D shape of the aneurysm and the distribution of thrombus.

Feasibility of Determination of Mechanical Properties of Abdominal Aortic Aneurysms by Simultaneous Pressure and Volume Measurements In-Vivo

2008 ◽  
Author(s):  
Marcel van ’t Veer ◽  
Marcel C. M. Rutten ◽  
Jaap Buth ◽  
Nico H. J. Pijls ◽  
Frans N. van de Vosse
Keyword(s):  
Mechanical Properties ◽  
Wall Stress ◽  
Tensile Tests ◽  
Aortic Aneurysms ◽  
Wall Material ◽  
Patient Specific ◽  
Abdominal Aortic ◽  
Risk Of Rupture

In an effort to better predict the risk of rupture of an abdominal aortic aneurysm (AAA), methods have been developed that comprise more than diameter information alone. Wall stress calculations demonstrated superior results compared to the diameter criterion [1]. Accurate wall stress calculations require patient specific geometry, load, and wall properties of the aneurysm [2]. Usually, values for mechanical properties obtained from in-vitro tensile tests of excised aneurysmal wall material are used for wall stress calculations [3]. For obvious reasons such experiments to obtain vessel properties are impossible to perform in patient specific cases for risk assessment.

scholarly journals Microstructure and mechanics of healthy and aneurysmatic abdominal aortas: experimental analysis and modelling

2016 ◽  
Vol 13 (124) ◽  
pp. 20160620 ◽  
Author(s):  
Justyna A. Niestrawska ◽  
Christian Viertler ◽  
Peter Regitnig ◽  
Tina U. Cohnert ◽  
Gerhard Sommer ◽  
...  
Keyword(s):  
Second Harmonic ◽  
Structural Parameters ◽  
Material Model ◽  
Biological Tissues ◽  
Aortic Aneurysms ◽  
Wall Structure ◽  
Collagen Fibres ◽  
Dispersion Parameters ◽  
Material Parameters

Soft biological tissues such as aortic walls can be viewed as fibrous composites assembled by a ground matrix and embedded families of collagen fibres. Changes in the structural components of aortic walls such as the ground matrix and the embedded families of collagen fibres have been shown to play a significant role in the pathogenesis of aortic degeneration. Hence, there is a need to develop a deeper understanding of the microstructure and the related mechanics of aortic walls. In this study, tissue samples from 17 human abdominal aortas (AA) and from 11 abdominal aortic aneurysms (AAA) are systematically analysed and compared with respect to their structural and mechanical differences. The collagen microstructure is examined by analysing data from second-harmonic generation imaging after optical clearing. Samples from the intact AA wall, their individual layers and the AAA wall are mechanically investigated using biaxial stretching tests. A bivariate von Mises distribution was used to represent the continuous fibre dispersion throughout the entire thickness, and to provide two independent dispersion parameters to be used in a recently proposed material model. Remarkable differences were found between healthy and diseased tissues. The out-of-plane dispersion was significantly higher in AAA when compared with AA tissues, and with the exception of one AAA sample, the characteristic wall structure, as visible in healthy AAs with three distinct layers, could not be identified in AAA samples. The collagen fibres in the abluminal layer of AAAs lost their waviness and exhibited rather straight and thick struts of collagen. A novel set of three structural and three material parameters is provided. With the structural parameters fixed, the material model was fitted to the mechanical experimental data, giving a very satisfying fit although there are only three material parameters involved. The results highlight the need to incorporate the structural differences into finite-element simulations as otherwise simulations of AAA tissues might not be good predictors for the actual in vivo stress state.

Sign in / Sign up

Export Citation Format

Share Document