Tracheal Stent Segmentation for Migration and Removal Trade-off
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Solution Overview
Problem
Endoprostheses face challenges in preventing migration within the body lumen while minimizing trauma during removal, as bare stents allow tissue ingrowth for stability but are difficult to remove, and fully covered stents prevent ingrowth but are prone to migration.
Innovation Solution
A tracheal stent design featuring a support structure with wave form structures and axial loop members made from nitinol wire, coated with a polymeric material, which extends radially outward to engage the tissue and prevent migration, and biodegradable spacer fins to reduce trauma upon removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bare stents are used to allow tissue ingrowth for stability, then migration prevention is improved, but removal trauma increases
Solution Approach 1:
The stent is segmented into different functional zones: a fully covered distal portion for migration prevention and a bare proximal portion for controlled tissue interaction. This segmentation allows each zone to perform its specific function independently, resolving the contradiction between stability and removable-ness
Solution Approach 2:
Different portions of the stent have different structural qualities - the distal end has full polymeric covering to prevent migration, while the proximal end has bare metal struts to allow controlled tissue ingrowth. This local differentiation enables the stent to simultaneously achieve migration prevention and controlled removability
2Object-affected harmful factors
If fully covered stents are used to prevent tissue ingrowth for easy removal, then removal trauma is reduced, but migration resistance worsens
Solution Approach 1:
The stent is divided into functional segments where the distal portion is fully covered for easy removal and the proximal portion is bare for migration resistance. This spatial segmentation resolves the contradiction by assigning different functions to different locations
Solution Approach 2:
The stent exhibits local quality variation with full polymeric coverage at the distal end for tissue-friendly removal and bare metal structure at the proximal end for anchoring stability, thus simultaneously achieving both goals
3Reliability
If axial loop members extend radially outward to engage tissue for migration prevention, then migration resistance is improved, but device complexity increases
Solution Approach 1:
The axial loop members are integrated directly into the wave form structures, combining the structural support function with the tissue engagement function. This merging reduces overall device complexity while maintaining migration resistance
Solution Approach 2:
The axial loop members serve multiple functions: they provide structural connectivity between wave forms, engage with tracheal tissue for anchoring, and maintain the radial profile. This multi-functionality reduces the need for additional components, simplifying the overall device
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
The design effectively prevents migration of the endoprosthesis while allowing tissue ingrowth for stability and reduces trauma during removal by using biodegradable components that degrade over time.
Implementation Method 1
at least some of the wave form structures include a nickel-titanium alloy
Implementation Method 2
at least some of the wave form structures are formed from nitinol wire
Implementation Method 3
A biodegradable filament is interwoven through the expandable metal structure
Data Source
AI summary
Tracheal stents may include a plurality of wave form structures each extending radially about the support structure, a plurality of axial loop members extending axially between adjacent wave form structures and a polymeric covering disposed thereover. Tracheal stents may include an expandable metal structure and a plurality of spacer fins extending above an outer surface of the expandable metal structure. The plurality of spacer fins may be formed of a material different than that of the expandable metal structure.