Stent with Staggered Key-Hole Bends for Low Profile Delivery
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Solution Overview
Problem
Prior art radially expandable stents face challenges in being crimped to a low profile due to high stress at bends, making it difficult to deliver them through small diameter, tortuous arteries, as the stress-relieving bends often abut and limit the crimped profile.
Innovation Solution
The stent design features serpentine ring structures with key-hole shaped bends in a staggered arrangement to avoid abutment, reducing stress and allowing for a smaller crimped profile, while maintaining strength and flexibility for deployment through narrow passageways.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If stress-relieving bends are added to reduce bending stresses at bends, then stress concentration is reduced, but the crimped profile size increases due to bend abutment
Solution Approach 1:
The patent applies asymmetry by staggering the key-hole shaped bends in an asymmetric pattern around the stent circumference. This asymmetric staggering prevents the bends from aligning and abutting against each other during crimping, thereby maintaining a compact profile while still providing stress relief at each bend location
Solution Approach 2:
The patent transitions from a two-dimensional arrangement where bends might align radially to a three-dimensional staggered arrangement. By distributing bends at different angular positions and depths around the stent structure, the bends occupy different spatial positions that prevent abutment during radial compression, reducing the crimped profile size
2Length of moving object
If the stent is crimped to a low profile for delivery through small diameter arteries, then deliverability is improved, but bending stress at the bends increases
Solution Approach 1:
The key-hole shaped bends are designed beforehand with extended geometry that provides built-in stress relief capacity. The extended shape of each bend acts as a cushioning feature that absorbs and distributes bending stresses during crimping, preventing stress concentration even when the stent is compressed to a low delivery profile
Solution Approach 2:
The patent changes the geometric parameters of the bends by extending them into key-hole shapes with increased radius and length. This parameter modification allows the bends to accommodate higher curvature changes during crimping without exceeding material stress limits, enabling smaller delivery profiles
3Stability of the object's composition
If connector members are used to join ring structures, then structural integrity is improved, but stress concentration at connector-bend junctions increases
Solution Approach 1:
The patent applies local quality by making the bends adjacent to connector members particularly robust with extended key-hole geometry. These locally enhanced bends provide additional stress relief capacity at the critical junction points where connector members meet the ring structures, preventing stress concentration while maintaining overall structural integrity
Data Source
AI summary
A stent is provided which can be crimped to a reduced profile with reduced stress in the stent, while maintaining the strength and flexibility of the stent so that it can be advanced through the narrow passageways present in a patient's body and then expanded to dilate and/or circumferentially support the vessel wall. Also provided is a method of deploying such a stent.