Helical Stent Strut Nesting for Smaller Crimped Profiles
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Solution Overview
Problem
Existing stents face a tradeoff between longitudinal flexibility, radial strength, and conformability to vessel curvature, with limited compressed profiles and interference between struts leading to stress/strain concentrations and interference, which can cause deformation and damage to coatings or catheters.
Innovation Solution
A stent design featuring a bent strut pattern with alternating long and short struts and a staggered loop alignment, allowing for a reduced crimped profile and enlarged expanded profile, while minimizing strut interference and stress/strain concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the stent is compressed to reduce the crimped diameter for delivery through tortuous vessels, then the compressed profile is reduced, but interference between adjacent struts and loops increases causing stress/strain concentrations and potential permanent deformation
Solution Approach 1:
The stent is segmented into alternating long and short struts with staggered loop alignment, creating distinct zones that distribute compression forces more evenly. This segmentation prevents concentrated stress at single points while maintaining the reduced crimped diameter necessary for delivery through tortuous vessels.
Solution Approach 2:
The patent introduces a staggered dimensional arrangement where loops are offset axially rather than aligned in a single plane. This dimensional change allows the stent to compress more uniformly in the radial direction without creating harmful stress concentrations between adjacent struts and loops.
2Strength
If the stent is designed with sufficient radial strength to support the vessel lumen when expanded, then radial support is improved, but longitudinal flexibility and conformability to vessel curvature are reduced
Solution Approach 1:
Different portions of the stent structure are given different qualities: the struts are designed with sufficient thickness and material properties to provide radial strength when expanded, while the loop regions and joint areas are designed with greater flexibility to allow longitudinal conformability. This local differentiation enables the stent to simultaneously achieve both radial support and longitudinal flexibility.
Solution Approach 2:
The stent structure incorporates dynamic characteristics where the alternating long and short struts with staggered loops create a configuration that can adapt its stiffness characteristics. When compressed during delivery, the structure is flexible for navigation; when expanded, the same structure provides rigid radial support through the geometric arrangement and material properties.
3Volume of moving object
If the stent is compressed beyond its elastic limit to achieve a smaller outside diameter, then the crimped profile is reduced, but the stent will not return to its desired deployed expanded diameter due to permanent deformation
Solution Approach 1:
The staggered loop alignment and alternating strut lengths create a structural configuration that cushions against excessive compression forces. This design prevents the stent from being compressed beyond its elastic limit by distributing forces more evenly throughout the structure, thereby preventing permanent deformation and ensuring reliable return to the deployed diameter.
Data Source
AI summary
The invention is directed to an endovascular device having an undulating pattern of struts and loops, where at least one strut has a bend in the crimped profile for reducing the compressed diameter. The strut configuration comprises one or more bent sections facing in opposite convex and concave orientations, thereby creating a space or hollow for an oppositely aligned portion of the device to nestle therein as the device is compressed. The undulating pattern may be staggered such that adjacent loops in the helical direction are axially offset with respect to a perpendicular axis perpendicular to the lengthwise direction, where a loop may be positioned to align with an adjacent strut in the helical direction. The device may include struts of varying lengths which may contribute to an enlarged expanded diameter of the device. The bent strut design of the crimped profile may be used with any endovascular strut design.