Esophageal Stent Loops and Flares for Anti-Migration Removal
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Solution Overview
Problem
Existing stents for treating esophageal strictures face high migration prevalence, particularly in fully covered designs, making repositioning and removal difficult due to vessel damage from protrusions, and are often indicated for permanent implantation.
Innovation Solution
A stent with anti-migration features, including radially extending loops and flared regions, allows for easy repositioning and removal by reducing the diameter through elongation, while maintaining secure placement with non-parallel angled features that minimize vessel damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If anti-migration protrusions are added to prevent stent migration, then stent stability is improved, but device complexity and potential for vessel damage increase
Solution Approach 1:
The anti-migration feature is segmented into multiple discrete protrusions distributed around the stent circumference rather than a single complex structure. Each protrusion is a simple extension of the tubular body, reducing overall device complexity while providing stable anchoring through multiple contact points with the vessel wall.
Solution Approach 2:
The protrusions are localized features extending from specific regions of the tubular body, concentrating the anti-migration function in discrete locations rather than requiring complex structures throughout the entire stent. This allows the majority of the stent to maintain its simple tubular geometry while achieving stability through localized modifications.
2Reliability
If the stent is designed for permanent implantation to prevent migration, then stent stability is improved, but ease of operation for repositioning and removal deteriorates
Solution Approach 1:
The protrusions are designed with elastic or shape memory properties that allow them to dynamically change their engagement with the vessel wall. During normal operation, they provide stable anchoring, but when sufficient radial compression force is applied during removal, they can be compressed radially inward to disengage from the vessel wall, enabling controlled repositioning or removal.
Solution Approach 2:
The mechanical properties of the protrusions (such as their radial stiffness or engagement force) are designed to change under specific conditions. During implantation and normal function, they maintain high engagement force for stability. During removal, applied compression forces change the engagement parameter, allowing the protrusions to disengage smoothly without causing vessel damage.
3Ease of operation
If the stent diameter is significantly reduced for removal, then ease of removal is improved, but the risk of causing vessel damage from protrusions increases
Solution Approach 1:
The protrusions are designed with parameter changes in their mechanical behavior during compression. As the stent diameter is reduced during removal, the protrusions undergo controlled deformation or disengagement, changing their interaction force with the vessel wall from high (during implantation) to low (during removal), preventing vessel damage even when significant diameter reduction is required.
Solution Approach 2:
The protrusions are designed with inherent compliance or cushioning characteristics that absorb the mechanical stress during diameter reduction. Their material properties or geometric design allow them to deform in a controlled manner during compression, cushioning the interaction with the vessel wall and preventing sharp forces that could cause damage during the removal process.
Data Source
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AI summary
An illustrative stent may comprise an elongated tubular member having a first end and a second end and an intermediate region disposed therebetween. The elongated tubular member configured to move between a collapsed configuration and an expanded configuration. The elongated tubular member may comprise at least one twisted filament, such as a knitted filament having a plurality of twisted knit stitches with intermediate rung portions extending between adjacent twisted knit stitches and one or more anti-migration features formed in one or more intermediate rung portions.