Braided Stent Radial Expansion Rings and Core Wire Delivery
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Solution Overview
Problem
Self-expanding braided stents face challenges in deploying the initial expanding end, high internal friction resisting radial expansion, difficulty in advancing through delivery sheaths, and recapturing after partial deployment, particularly in neurovascular procedures where precision and minimization of trauma are critical.
Innovation Solution
Incorporating radial expansion rings at the initial and later deployment ends of the stent, along with a core advancement wire to reduce friction and facilitate deployment, and enable recapture of the stent within the delivery sheath, utilizing shape memory materials and attachment tabs for secure fixation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a self-expanding braided stent is designed to expand radially to reinforce the blood vessel, then the stent provides structural support and prevents restenosis, but high internal friction resists the radial expansion force and prevents full opening of the initially expanding end
Solution Approach 1:
The stent is divided into multiple segments including a distal end, proximal end, and intermediate portion. The distal end is designed with specific braiding characteristics that differ from the proximal end, allowing the distal end to expand more readily while the proximal end maintains structural support. This segmentation resolves the contradiction by distributing expansion forces differently across stent segments.
Solution Approach 2:
Different portions of the stent are given different local properties: the distal end has a lower braid angle and fewer interwoven cycles compared to the proximal end, making it more compliant and easier to expand initially. The proximal end maintains higher structural integrity. This local differentiation allows the stent to overcome internal friction at the expansion front while maintaining overall strength.
2Ease of operation
If traditional delivery systems push the braided stent distally by advancing a blunt surface against the proximal end, then the stent can be advanced through the delivery system, but the application of force on the proximal end causes axial compression and radial expansion within the delivery sheath, increasing friction
Solution Approach 1:
Instead of pushing the stent from the proximal end, the delivery system applies force to the distal end or uses a pusher that engages the intermediate portion. This reverses the traditional approach and prevents premature radial expansion of the stent within the delivery sheath, reducing friction between the stent and sheath during advancement.
Solution Approach 2:
A pusher or advancement device acts as an intermediary between the operator and the stent. This intermediary transmits force in a controlled manner to the distal end or intermediate portion of the stent, preventing direct compression of the proximal end that would cause unwanted radial expansion and increased friction with the delivery sheath.
3Manufacturing precision
If the initially expanding end of the braided stent does not open fully and quickly, then the material and dimension provide some expansion, but deployment accuracy is affected and placement becomes difficult
Solution Approach 1:
The braid angle, wire diameter, and interwoven cycle count are varied along the length of the stent. The distal end has a smaller braid angle and fewer interwoven cycles, creating a gradient that facilitates easier and more complete expansion at the leading end. This parameter variation ensures accurate deployment while maintaining ease of opening.
4Reliability
If a braided stent is designed with high structural integrity to prevent restenosis, then the stent provides reliable reinforcement, but the stent cannot be recaptured after partial deployment
Solution Approach 1:
The stent is designed with dynamic properties that allow it to transition between a compressed delivery state and an expanded deployed state. The braided structure incorporates elements that can be compressed during delivery and then expand when released. This dynamic design enables recapture capability while maintaining structural integrity when deployed, as the stent can be re-compressed into the delivery system if needed.
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
Enhances the radial expansion force for reliable deployment and fixation of the stent, reduces friction during delivery, and allows for recapture of the stent after partial deployment, improving the accuracy and safety of neurovascular interventions.
Implementation Method 1
one or more expansion rings... having a compressed configuration having a first diameter and an expanded configuration having a second diameter larger than the first diameter
Implementation Method 2
Incorporating radial expansion rings at the initial and later deployment ends of the stent, along with a core advancement wire to reduce friction and facilitate deployment
Data Source
AI summary
A self-expanding braided stent includes at least a distal radial expansion ring added to a distal end of the stent body to increase a radial expansion force of the self-expanding braided stent in deployment of the stent, and to facilitate advancement of the stent through a delivery sheath by a core advancement wire. A proximal radial expansion ring is optionally added to a proximal end of the stent body to allow the stent to be recaptured following partial deployment by retraction of the core advancement wire, prior to full deployment of a proximal portion of the stent body.