Flexible Stent Prosthesis with Segmented Radial Stiffness
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Solution Overview
Problem
Existing branch vessel prostheses face challenges in maintaining structural integrity and flexibility within the dynamic and pulsatile environment of the body, particularly when deployed within fenestrations of main body prostheses, leading to potential weakening and crushing due to cyclic stress.
Innovation Solution
A prosthesis design featuring an expandable tubular frame with varying radial stiffness and flexibility, including a transition segment with peak-to-peak annular stent members and a flex segment with peak-to-valley apices, coupled with longitudinal tie bars, to provide both radial strength and bending flexibility, ensuring securement within fenestrations while resisting crushing forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the branch vessel prosthesis is made highly flexible to track through tortuous luminal environments, then it can conform to the luminal environment, but it becomes vulnerable to crushing under cyclic stress from the main body prosthesis
Solution Approach 1:
The prosthesis is divided into multiple segments including a first region with first radial stiffness and a second region with second radial stiffness. The first region includes a first annular segment with coupled apices providing structural strength, while the second region includes a second annular segment with uncoupled apices providing flexibility. This segmentation allows different parts of the prosthesis to have different mechanical properties to simultaneously satisfy both strength and flexibility requirements.
Solution Approach 2:
Different regions of the prosthesis are assigned different radial stiffness characteristics tailored to their specific functional requirements. The first region (with coupled apices) is designed with higher radial stiffness to resist crushing forces, while the second region (with uncoupled apices) is designed with lower radial stiffness to provide flexibility for tracking through tortuous lumens. This local differentiation of mechanical properties resolves the contradiction between overall flexibility and localized strength.
2Strength
If the prosthesis includes a balloon-expandable stent for sufficient resilience, then it can withstand pulsatile luminal environment, but it hinders balloon expansion and molding
Solution Approach 1:
The prosthesis employs a self-expanding mechanism where the stent frame is constructed with elastic memory properties that allow it to automatically expand to its predetermined shape after delivery. The first annular segment with coupled apices provides structural resilience to withstand pulsatile forces, while the second annular segment with uncoupled apices allows controlled flexibility during expansion. This dynamic design eliminates the need for separate balloon expansion while maintaining both strength and manufacturability.
Data Source
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AI summary
A prosthesis is disclosed including an expandable frame (50) having a first region (F) and a second region (S) coupled to one another. The first region (F) includes a transition segment (200) and a flex segment (202). The stent members of the transition segment have proximal and distal apices arranged in a peak-to-peak relationship with one another. At least a portion of proximal and distal apices of the transition segment remains uncoupled to one another. The flex segment (202) includes a stent member having proximal and distal apices arranged in a peak-to-valley relationship with the transition segment. Longitudinal tie bars (270) are intermittently coupled between apices the flex segment and the transition segment at coupling joints. The coupling joint is located where the proximal and distal apices of the stent members of the transition segment remain uncoupled to one another. The transition and flex segments may form an alternating pattern. A flareable proximal portion may be included.