Stent Helical Fin Strut Alignment for Radial Strength
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Stents with helical structures often weaken and are prone to fractures under biomechanical forces, compromising their radial strength and fatigue resistance while maintaining flexibility, which is a challenge in vascular applications.
Innovation Solution
A stent design featuring a tubular frame with a longitudinally extending helical fin where the angle of struts is substantially aligned with the helix angle, providing enhanced radial strength and fatigue resistance while maintaining flexibility, and incorporating a method for forming the stent using a mandrel and helical former to deform the material into the desired shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a helical structure is introduced into a stent frame, then fluid flow patterns are improved and turbulence is reduced, but the stent frame becomes weakened and prone to fractures
Solution Approach 1:
The patent applies local quality by creating a helical fin structure that is localized to specific regions of the stent frame rather than uniformly modifying the entire structure. The fin protrudes radially inwardly from the tubular frame, concentrating the flow-modifying geometry in a targeted manner while preserving the overall frame integrity. This localized approach allows the helical flow induction function to be achieved without compromising the global structural strength of the stent.
Solution Approach 2:
The patent introduces a new dimensional element by adding a radially protruding fin component to the traditional planar stent frame. This fin extends in the radial dimension, creating a three-dimensional helical structure that interacts with the fluid flow without significantly altering the primary circumferential and longitudinal dimensions of the frame. This dimensional addition enables flow control functionality while maintaining frame strength.
2Strength
If the stent is made with sufficient radial strength to resist compression, then the stent maintains its expanded configuration, but the stent becomes less flexible
Solution Approach 1:
The patent employs dynamics by utilizing the elastic properties of nitinol material that allows the stent frame to dynamically respond to external forces. The frame can be compressed to a smaller diameter for insertion and then spontaneously expands to its original larger diameter upon deployment, demonstrating dynamic shape transformation. This dynamic behavior enables the stent to exhibit both flexibility during insertion and sufficient radial strength when expanded, resolving the contradiction between these two requirements.
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 improved resistance against radial forces and fatigue, preventing fractures while maintaining flexibility and promoting desirable fluid flow patterns, such as helical or spiral flow, within the vessel.
Implementation Method 1
Nitinol is a shape memory alloy that undergoes a phase transformation from a weaker more deformable martensite phase exposed to low temperatures to a stronger austenite phase when exposed to certain higher temperatures
Implementation Method 2
Nitinol is a shape memory alloy that undergoes a phase transformation from a weaker more deformable martensite phase exposed to low temperatures to a stronger austenite phase when exposed to certain higher temperatures
Implementation Method 3
WO00/38591 discloses the concept of a spiral formation on the internal surface of stents to induce desirable helical flow in blood flowing through the lumen of the stent. Generating a helical or spiral flow pattern in the blood serves to reduce turbulence and dead spots
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A stent (1) comprising a tubular frame (2) comprising a first end (3) and a second end and a longitudinal axis (4) therebetween. The frame (2) comprises a plurality of struts (9) defining a generally cylindrical portion comprising a longitudinally extending helical fin (11) protruding radially inwardly and having a helix angle. The angle, relative to the longitudinal axis (4), of at least some of the struts (9) in the helical fin (11) is substantially aligned with the helix angle of the helical fin (11).