Variable Diameter Ring Fixation for Endoluminal Stent Grafts
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Solution Overview
Problem
Stent grafts used to treat vascular aneurysms face challenges such as instability, kinking, obstruction, disintegration, and endoleaks due to inadequate sealing and fixation, particularly in larger displacement forces and smaller diameter stent graft portions, which can lead to relapse of the treated conditions.
Innovation Solution
An endoluminal device comprising a stent with a tubular graft and variable diameter rings made of coiled wire, preferably nitinol, which provides enhanced sealing and fixation by circumferential apposition to the vessel wall through radial force, ensuring stable placement and exclusion of aneurysms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional stent grafts are used without additional fixation mechanisms, then the device structure remains simple, but the stent graft becomes unstable and susceptible to migration, kinking, and endoleaks
Solution Approach 1:
The fixation mechanism is divided into separate components: the stent graft body and the variable diameter ring are distinct elements that work together. The ring can be deployed independently to provide fixation without complicating the overall stent graft structure
Solution Approach 2:
The variable diameter ring is nested within or integrated with the stent graft structure, allowing it to be delivered through the same catheter system while providing additional fixation functionality without significantly increasing external device complexity
2Adaptability or versatility
If the stent graft diameter is reduced to treat smaller vessels, then the device becomes more versatile, but displacement forces increase causing instability and migration
Solution Approach 1:
The variable diameter ring is deployed before the stent graft to pre-establish fixation points in the vessel wall. This preliminary action creates anchor points that resist subsequent displacement forces from smaller diameter grafts
Solution Approach 2:
The fixation mechanism provides localized reinforcement at specific sites along the stent graft. The variable diameter ring concentrates fixation force at critical locations rather than distributing it uniformly, addressing the increased displacement forces in smaller vessels
3Ease of operation
If the stent graft is made flexible to navigate tortuous vessels, then ease of insertion improves, but sealing capability at the aneurysm ends deteriorates
Solution Approach 1:
The stent graft is divided into flexible intermediate sections for navigation and rigid sealing zones at the ends. The variable diameter ring reinforces the sealing zones without compromising the flexibility of the main graft body
Solution Approach 2:
Different sections of the stent graft have different mechanical properties: the main body remains flexible for navigation while the ends with variable diameter rings provide rigid sealing. This local differentiation maintains both ease of insertion and sealing capability
4Force
If frictional forces alone are used for fixation, then the device structure remains simple, but fixation strength is insufficient under larger displacement forces
Solution Approach 1:
The variable diameter ring is deployed in advance to create mechanical interlocking with the vessel wall before the stent graft is fully expanded. This preliminary fixation provides immediate anchor points that supplement frictional forces
Solution Approach 2:
The fixation system combines multiple mechanisms: frictional forces from the stent graft apposition and mechanical interlocking from the variable diameter ring. This composite approach provides superior fixation strength without requiring a single complex anchoring mechanism
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
The device achieves a secure seal and fixation at the aneurysm ends, reducing the risk of relapse and complications like endoleaks, while maintaining vascular patency and integrity, even in smaller vessel lengths.
Implementation Method 1
The ring is preferably a nitinol ring. The ring may be a self-expanding ring of a balloon-expandable ring.
Data Source
AI summary
This invention is an endoluminal device including a stent; a tubular graft supported by the stent, wherein the graft comprises a proximal opening and a distal opening; and a variable diameter ring adjacent one of said openings, wherein the variable diameter ring comprises a coiled length of wire having two ends and forming at least one winding around the tubular graft. This invention also relates to the methods of treating an aneurysm and making the endoluminal device.