Self-Expanding Stent Wavy-Line Geometry for Gap Reduction
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Solution Overview
Problem
Self-expandable stents face challenges in achieving good coverage, maintaining expansive force, and axial pliability, with existing designs often resulting in increased gaps that can lead to tissue growth and restenosis, and being either too rigid or too flexible when inserted into lumens like blood vessels or biliary ducts.
Innovation Solution
A self-expandable stent design featuring wavy-line annular bodies with shared linear portions that integrate adjacent elements, providing a uniform expansive force and maintaining pliability in the axial direction, with specific configurations of bent linear portions and shared linear portions to enhance coverage and stability during expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the stent is self-expanded from a highly compressed state (3.75-7.5 times expansion ratio), then the stent can be delivered through a small sheath, but the gap between elements increases after expansion
Solution Approach 1:
The stent is divided into multiple wavy-line annular bodies arranged in the axial direction, with each annular body consisting of multiple bent linear portions. This segmentation allows the stent to be compressed into a small delivery profile while maintaining element integrity and reducing gaps when expanded
Solution Approach 2:
The stent employs wavy-line annular bodies with curved configurations instead of straight elements. The curved geometry allows for more efficient packing during compression and better distribution of expansive force during expansion, reducing gaps between elements while maintaining deliverability through small sheaths
2Reliability
If the line width of each element is made small to improve coverage, then the stent coverage improves, but the expansive force becomes weak
Solution Approach 1:
The wavy-line configuration of annular bodies provides mechanical advantage through curved geometry, allowing thinner elements to generate sufficient expansive force. The curved paths distribute stress more effectively, enabling thin elements to maintain both coverage and expansive capability
Solution Approach 2:
Dividing the stent into multiple wavy-line annular bodies allows each segment to contribute to both coverage and expansive force. The segmented structure with bent linear portions creates multiple force vectors that collectively provide strong expansion while maintaining thin element profiles for good coverage
3Force
If the stent is made rigid to maintain shape during expansion, then the expansive force is strong, but the stent becomes too rigid to navigate bent lumens
Solution Approach 1:
The wavy-line annular bodies with curved geometries provide inherent flexibility while maintaining structural integrity. The curved configuration allows the stent to bend and conform to luminal geometry during navigation, yet generates sufficient expansive force when deployed
Solution Approach 2:
The stent structure transitions from a flexible, conformable state during delivery and navigation to a rigid, expansive state when deployed. The wavy-line configuration dynamically adjusts, allowing bending during insertion but providing strong radial force when expanded to maintain lumen patency
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 stent achieves effective expansion with good coverage and a sufficient expansive force while maintaining pliability, reducing the risk of restenosis and tissue stimulation, and is suitable for various luminal applications.
Implementation Method 1
The present applicant has also suggested a stent (JP-A-8-000738) in which a superelastic pipe is cut out and manufactured by a laser or the like.
Implementation Method 2
The stent is self-expanded from 3.75 times to 7.5 times on an external diameter basis when being discharged from the sheath
Data Source
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AI summary
A self-expandable stent (1) has a plurality of wavy-line annular bodies (2) in the axial direction. Each wavy-line annular body (2) of the stent (1) other than those at one and the other ends has a first shared linear portion (A1) and a second shared linear portion (A2) located on one end side, a third shared linear portion (A3) and a fourth shared linear portion (A4) located on the other end side, a first bent linear portion (21a) coupled with the first and third shared linear portions, a second bent linear portion (22a) coupled with the third and second shared linear portions, a third bent linear portion (23a) coupled with the second and fourth shared linear portions, and a fourth bent linear portion (24a) coupled with the fourth and first shared linear portions. Two out of the four bent linear portions have the same number of bends and substantially the same form at the time of inversion, and the other two out of the four bent linear portions have the same number of bends which is different from the number of bends of the above-mentioned two bent linear portions and substantially the same form at the time of inversion.