Composite Stent Graft Segmentation for Kinking and Stenosis
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Solution Overview
Problem
The deployment of branch stent grafts from main stent grafts into side arteries is challenging due to kinking issues with flexible stents and distortion or stenosis with rigid stents, particularly in aneurysmed spaces, and maintaining secure attachment within fenestrations is difficult.
Innovation Solution
A composite stent graft design featuring a balloon expandable stent portion for rigidity across aneurysmed spaces and self-expanding stents for flexibility within side branches, with a flared extension to secure attachment within fenestrations, using biocompatible materials like polytetrafluoroethylene and collagen-based materials, and shape memory alloys for stent components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a flexible self-expanding stent graft is used, then the stent graft can accommodate movement in aneurysmed spaces, but the side branch can kink and close off the lumen
Solution Approach 1:
The stent graft is divided into distinct segments: a proximal self-expanding stent portion for flexibility in aneurysmed spaces, and a distal balloon-expandable stent portion for rigidity in side branches. This segmentation allows each portion to have optimized properties for its specific functional requirement.
Solution Approach 2:
Different portions of the stent graft are assigned different mechanical properties: the proximal end uses self-expanding stents for flexibility and movement accommodation, while the distal end uses balloon-expandable stents for rigidity and kinking resistance. This local differentiation resolves the contradiction between flexibility and kinking resistance.
2Strength
If a rigid balloon expandable stent graft is used, then the stent graft maintains structural integrity, but the distal end causes distortion and fibrosis of the side branch vessel
Solution Approach 1:
The stent graft is segmented into a proximal self-expanding portion and a distal balloon-expandable portion, allowing the rigid distal end to be confined to the fenestration area while the flexible proximal end extends into the side branch, reducing distortion and fibrosis.
Solution Approach 2:
The distal balloon-expandable portion provides localized structural integrity at the fenestration site, while the proximal self-expanding portion provides flexibility within the side branch. This local quality differentiation maintains strength where needed while minimizing harmful effects.
3Adaptability or versatility
If the stent graft is made flexible to prevent kinking, then kinking is reduced, but the stent graft cannot maintain position securely in the fenestration
Solution Approach 1:
The stent graft is divided into flexible and rigid segments, with the rigid balloon-expandable distal portion providing anchoring in the fenestration while the flexible proximal portion prevents kinking. This segmentation simultaneously achieves position stability and flexibility.
Solution Approach 2:
The distal balloon-expandable portion provides localized position stability through rigid structure in the fenestration, while the proximal self-expanding portion provides flexibility to prevent kinking. This local quality differentiation resolves the contradiction between stability and flexibility.
4Strength
If a balloon expandable stent is used at the distal end, then structural integrity is maintained, but stenosis occurs at the distal end of the side graft
Solution Approach 1:
The distal balloon-expandable portion is designed with specific structural characteristics (such as struts and expansion geometry) that provide structural integrity while minimizing stenosis. The local quality of the stent structure is optimized to balance strength and stenosis prevention.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design prevents kinking and stenosis by providing necessary flexibility within side branches while maintaining structural integrity across aneurysmed spaces, ensuring secure attachment and reducing fibrosis and distortion risks.
Implementation Method 1
a balloon expandable stent portion
Implementation Method 2
self expanding stents associated with the tubular graft material portion
Implementation Method 3
shape memory alloys for stent components
Data Source
AI summary
A composite stent graft has a balloon expandable stent portion (3), a tubular graft material portion (1) inside or outside of the balloon expandable stent portion and self expanding stents (5) associated with the tubular graft material portion. Part (7) of the balloon expandable stent portion can extend beyond the proximal end (9) of the tubular graft material portion. The tubular graft material can be polytetrafluoroethylene, Dacron, Thoralon™, polyamide, small intestine submucosa, collagenous extracellular matrix material, or any other suitable biocompatible material. A method of deploying which includes flaring a part (7) of the balloon expandable stent portion is also discussed.