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BackgroundWe aimed to develop a simple structural model of aortic aneurysms using computer‐assisted drafting (CAD) in order to create a basis of definition for saccular aortic aneurysms.Methods and ResultsWe constructed a simple aortic aneurysm model with 2 components: a tube similar to an aorta and an ellipse analogous to a bulging aneurysm. Three parameters, including the vertical and horizontal diameters of the ellipse and the fillet radius, were altered in the model. Using structural analysis with the finite element method, we visualized the distribution of the maximum principal stress (MPS) in the aortic wall and identified the area(s) of prominent stress. We then selected patients with thoracic aortic aneurysms in whom the aneurysm expansion rates were followed up and applied the theoretical results to the raw imaging data. The maximum MPS drastically increased at areas where the aspect ratio (vertical/horizontal) was <1, indicating that “horizontally long” hypothetical ellipses should be defined as “saccular” aneurysms. The aneurysm expansion rate for the patients with thoracic aneurysms conforming to these parameters was significantly high. Further, “vertically long” ellipses with a small fillet might be candidates for saccular aneurysms; however, the clinical data did not support this.ConclusionsBased on the biomechanical analysis of a simple aneurysm model and the clinical data of the thoracic aortic aneurysms, we defined “horizontally long” aortic aneurysms with an aspect ratio of <1 as “saccular” aneurysms.

Degradation of vinyl polymers remains a challenge because of the robust main‐chain CC bonds. In this study, we designed novel pendant‐responsive comonomers with a carbon–halogen bond, which can be copolymerized with vinyl monomers to enable facile degradation of the CC backbone upon triggering stimulus. The comonomer unit was designed to induce interlocking degradation, that is, it first generates side‐chain radical upon trigger, subsequently provides a main‐chain radical via intramolecular 1,5‐shift, and then finally causes the main‐chain cleavage via β‐scission. A remarkable decrease in molecular weight was observed when the obtained copolymer was treated with a copper catalyst, and the effect of polymer structure was assessed on the interlocking degradation behavior.