Department of Bioengineering, Stanford University, Stanford, California, USA.
J Endovasc Ther. 2011 Aug;18(4):559-68. doi: 10.1583/11-3472.1.
To evaluate the biomechanical and hemodynamic forces acting on the intermodular junctions of a multi-component thoracic endograft and elucidate their influence on the development of type III endoleak due to disconnection of stent-graft segments.
Three-dimensional computer models of the thoracic aorta and a 4-component thoracic endograft were constructed using postoperative (baseline) and follow-up computed tomography (CT) data from a 69-year-old patient who developed type III endoleak 4 years after stent-graft placement. Computational fluid dynamics (CFD) techniques were used to quantitate the displacement forces acting on the device. The contact stresses between the different modules of the graft were then quantified using computational solid mechanics (CSM) techniques. Lastly, the intermodular junction frictional stability was evaluated using a Coulomb model.
The CFD analysis revealed that curvature and length are key determinants of the displacement forces experienced by each endograft and that the first 2 modules were exposed to displacement forces acting in opposite directions in both the lateral and longitudinal axes. The CSM analysis revealed that the highest concentration of stresses occurred at the junction between the first and second modules of the device. Furthermore, the frictional analysis demonstrated that most of the surface area (53%) of this junction had unstable contact. The predicted critical zone of intermodular stress concentration and frictional instability matched the location of the type III endoleak observed in the 4-year follow-up CT image.
The region of larger intermodular stresses and highest frictional instability correlated with the zone where a type III endoleak developed 4 years after thoracic stent-graft placement. Computational techniques can be helpful in evaluating the risk of endograft migration and potential for modular disconnection and may be useful in improving device placement strategies and endograft design.
评估多组件胸主动脉覆膜支架内移植物各模块连接处的生物力学和血流动力学作用力，并阐明其对支架-移植物段分离导致 III 型内漏发展的影响。
使用一位 69 岁患者的术后（基线）和随访 CT 数据构建胸主动脉和 4 组件胸主动脉覆膜支架的三维计算机模型，该患者在支架-移植物置入 4 年后发生 III 型内漏。采用计算流体动力学（CFD）技术量化作用于该装置的位移力。然后，使用计算固体力学（CSM）技术量化移植物不同模块之间的接触应力。最后，使用库仑模型评估模块连接处的摩擦稳定性。
CFD 分析表明，曲率和长度是每个移植物所受位移力的关键决定因素，前 2 个模块在横向和纵向轴上均受到相反方向的位移力作用。CSM 分析表明，装置第 1 个和第 2 个模块之间的连接处的应力集中最高。此外，摩擦分析表明，该连接处的大部分表面积（53%）具有不稳定的接触。预测的模块间应力集中和摩擦不稳定的临界区域与 4 年随访 CT 图像中观察到的 III 型内漏的位置相吻合。
较大的模块间应力和最高的摩擦不稳定区域与胸主动脉支架-移植物置入 4 年后 III 型内漏发生的区域相关。计算技术有助于评估移植物迁移和模块分离的风险，可能有助于改进装置放置策略和移植物设计。
