Hinged Stent Structure for Flexible Vessel Conformity
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Solution Overview
Problem
Existing stent structures face challenges in maintaining longitudinal strength while achieving flexibility to conform to curved lumens, as making parts more flexible often results in reduced radial and longitudinal strength, potentially leading to device failure and migration.
Innovation Solution
Incorporating hinged coupling elements made of shape memory material, such as Nitinol, which allow the stent sections to pivot, providing flexibility without compromising longitudinal stability, by heat-treating specific zones to elevate their transition temperature above body temperature, ensuring they remain malleable and generate minimal return force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If parts of the stent are made more flexible to conform to curved lumens, then longitudinal flexibility is improved, but radial and longitudinal strength is reduced
Solution Approach 1:
The stent is divided into distinct rigid stent sections and flexible coupling elements. The coupling elements are further segmented into hinge portions (for flexibility) and tie bar portions (for strength). This segmentation allows different parts of the stent to have different mechanical properties, enabling longitudinal flexibility at the hinges while maintaining radial and longitudinal strength through the rigid stent sections and tie bar portions.
Solution Approach 2:
Different portions of the stent structure are given different mechanical qualities. The hinge portions are designed to be flexible with reduced cross-sectional area, while the tie bar portions and stent sections maintain full strength. This local differentiation of material properties allows the stent to have both flexible regions for conforming to curved lumens and strong regions for providing structural support.
2Adaptability or versatility
If the stent is made more conformable to fit curved lumens, then adaptability is improved, but the force generated can cause stress on the lumen by urging it into an unnatural configuration
Solution Approach 1:
The stent structure segments the force-generating components from the flexible components. The rigid stent sections generate radial expansion force for lumen support, while the flexible coupling elements with hinges allow longitudinal bending without generating excessive straightening forces. This segmentation prevents the harmful effect of strong straightening forces on curved lumens while maintaining necessary radial support.
Solution Approach 2:
The coupling elements are designed to be dynamically flexible rather than statically rigid. The hinges allow the coupling elements to adapt their configuration based on the lumen's natural curvature, reducing the generation of harmful straightening forces while maintaining structural integrity and radial support capabilities.
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 hinged stent structure achieves enhanced longitudinal flexibility and stability, preventing unnecessary stress on vessel walls and maintaining device position, particularly beneficial for delicate vessels by retaining radial and longitudinal strength.
Implementation Method 1
heat treat a part of the shape memory structure in order to raise its transition temperature, for example to significantly above body temperature. So doing causes that part to remain in its martensitic phase when in the patient and to remain malleable
Implementation Method 2
made for example of a shape memory material such as Nitinol
Data Source
AI summary
A stent (10) is provided with a plurality of stent rings (12) formed of a plurality of interconnected struts (14). Adjacent stent rings (12) are coupled to one another by a plurality of tie bars (16). Within each tie bar (16) there is provided a hinge (36) which facilitates the curving of the stent (10) in its longitudinal direction and minimizes the generation of returning force to a non-curved configuration by the stent (10). The hinge could, for example, be formed by heat treating a portion of the tie bar (16). This arrangement is particularly suitable for stents or other medical devices intended to be placed in delicate vessels, such as cerebral vessels.