Reyna Vivian, Fathesami Niusha, Wu Wei, Muluk Satish C, De Oliveira Victor, Finol Ender A
Department of Mechanical Engineering, University of Texas at San Antonio, San Antonio, TX, USA.
Department of Biomedical Engineering, University of Texas at San Antonio, San Antonio, TX, USA.
Cardiovasc Eng Technol. 2025 Feb;16(1):66-78. doi: 10.1007/s13239-024-00757-8. Epub 2024 Oct 28.
An abdominal aortic aneurysm (AAA) is a dilation localized in the infrarenal segment of the abdominal aorta that can expand continuously and rupture if left untreated. Computational methods such as finite element analysis (FEA) are widely used with in silico models to calculate biomechanical predictors of rupture risk while choosing constitutive material properties for the AAA wall and intraluminal thrombus (ILT).
In the present work, we investigated the effect of different constitutive material properties for the wall and ILT on 21 idealized and 10 unruptured patient-specific AAA geometries. Three material properties were used to characterize the wall and two for the ILT, leading to six material model combinations for each AAA geometry subject to appropriate boundary conditions.
The results of the FEA simulations indicate significant differences in the average peak wall stress (PWS), 99th percentile wall stress (99th WS), and spatially averaged wall stress (SAWS) for all AAA geometries subject to the choice of a material model combination. Specifically, using a material model combination with a compliant ILT yielded statistically higher wall stresses compared to using a stiff ILT, irrespective of the constitutive equation used to model the AAA wall.
This work provides quantitative insight into the variability of the wall stress distributions ensuing from AAA FEA modeling due to its strong dependency on population-averaged soft tissue material characterizations. This dependency leads to uncertainty about the true biomechanical state of stress of an individual AAA and the subsequent assessment of its rupture risk.
腹主动脉瘤（AAA）是腹主动脉肾下段的局限性扩张，如果不治疗，其会持续扩大并破裂。诸如有限元分析（FEA）等计算方法在计算机模型中被广泛使用，以计算破裂风险的生物力学预测指标，同时为腹主动脉瘤壁和腔内血栓（ILT）选择本构材料特性。
在本研究中，我们研究了壁和ILT的不同本构材料特性对21个理想化和10个未破裂的患者特异性腹主动脉瘤几何形状的影响。使用三种材料特性来表征壁，两种用于ILT，从而为每个腹主动脉瘤几何形状产生六种材料模型组合，并施加适当的边界条件。
有限元分析模拟结果表明，对于所有腹主动脉瘤几何形状，根据材料模型组合的选择，平均峰值壁应力（PWS）、第99百分位数壁应力（第99百分位数WS）和空间平均壁应力（SAWS）存在显著差异。具体而言，与使用硬ILT相比，使用具有顺应性ILT的材料模型组合在统计学上产生更高的壁应力，而与用于模拟腹主动脉瘤壁的本构方程无关。
由于其强烈依赖于群体平均软组织材料特征，这项工作为腹主动脉瘤有限元分析建模所产生的壁应力分布的变异性提供了定量见解。这种依赖性导致对个体腹主动脉瘤的真实生物力学应力状态及其破裂风险的后续评估存在不确定性。
