Stent Axial Stretch Restriction Sheath Release
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Solution Overview
Problem
Stents with spirally wound wire rods face increased resistance and axial stretching issues when released from sheaths, leading to improper placement in the body lumen due to high contact areas and axial reduction rates during expansion.
Innovation Solution
A stent with a tubular skeleton portion that is both expandable and contractable, featuring a stretch restriction portion made of a different material, which restricts axial stretching when contracted, allowing for proper release from the sheath and reduced axial reduction rates during expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the skeleton portion is made stretchable in the axial direction to facilitate release from the sheath, then the ease of operation is improved, but the axial reduction rate increases when expanding, worsening the placement precision
Solution Approach 1:
The stent employs dynamic characteristics by being stretchable in the axial direction during release from the sheath, then transforming to a substantially non-stretchable state during expansion to minimize axial reduction. This dynamic behavior allows the stent to adapt its mechanical properties to different operational phases, solving both the release ease and placement precision requirements.
Solution Approach 2:
The stent changes its axial stretchability parameter from a stretchable state during sheath release to a substantially non-stretchable state during expansion. This parameter change is achieved through the specific structural design that allows controlled stretching during delivery but limits axial deformation during deployment, thereby resolving the contradiction between ease of release and placement precision.
2Volume of moving object
If the skeleton portion contracts in the radial direction to fit in the sheath, then the volume of the stent is reduced for delivery, but the contact area with the sheath increases, worsening the resistance during release
Solution Approach 1:
The stent dynamically adjusts its radial contraction characteristics: it contracts sufficiently to fit within the sheath for delivery, but the structural design ensures that during release, the contraction is optimized to minimize contact area and resistance. The specific configuration allows the stent to transition from a highly contracted delivery state to an expanded deployment state with controlled interaction with the sheath.
Solution Approach 2:
The stent structure exhibits local quality variations where different portions have different mechanical properties. The skeleton portion is designed with specific structural characteristics that allow radial contraction for sheath accommodation while maintaining properties that minimize axial stretching and contact resistance during release, resolving the contradiction between compact delivery and easy release.
3Reliability
If the skeleton portion is designed to expand in the radial direction to treat the lesion, then the therapeutic effect is improved, but the axial reduction rate increases, worsening the placement accuracy
Solution Approach 1:
The stent is designed to be dynamically stretchable in the axial direction during the release process from the sheath, but substantially non-stretchable during the expansion phase. This dynamic behavior ensures that while the stent can achieve full radial expansion for therapeutic effectiveness, it maintains placement accuracy by minimizing axial reduction during the critical expansion phase.
Solution Approach 2:
The stent changes its axial stretchability parameter based on the operational phase: stretchable during sheath release to facilitate delivery, but substantially non-stretchable during expansion to maintain placement accuracy. This parameter change resolves the contradiction between achieving sufficient radial expansion for therapy and maintaining placement precision.
Data Source
AI summary
This covered stent 100, which is released from a sheath 200 and placed in a lumen in a living body, is provided with: a tubular skeleton portion 11 which is stretchable in the axial direction and is expandable in the radial direction substantially perpendicular to the axial direction; and a stretch restriction portion 2 for restricting stretching of the skeleton portion in the axial direction. The stretch restriction portion is formed from a material different from that of the skeleton portion and restricts stretching of the skeleton portion in the axial direction when the skeleton portion is contracted in the radial direction while being stored in the sheath.