Segmented Stent Graft Flexibility and Kink Resistance
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Solution Overview
Problem
Current stent grafts face challenges in maintaining flexibility and preventing cellular infiltration, particularly when navigating extreme anatomical curves, and existing methods for encapsulation are either labor-intensive or result in inflexible devices.
Innovation Solution
A stent graft design featuring a stent frame with a central axis, encapsulated by graft members with expansion portions that allow for longitudinal elongation and contraction, maintaining a constant effective cross-sectional area even in severe curvatures, and a method of manufacturing that involves tensioning and relaxing the stent frame to achieve the desired flexibility and kink resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a stent graft is encapsulated with ePTFE to prevent cellular infiltration, then cell infiltration is prevented, but the device becomes inflexible and cannot accommodate extreme anatomical curves
Solution Approach 1:
The graft covering is divided into multiple discrete segments rather than being a continuous monolithic structure. These segmented graft portions are spaced apart along the stent frame, creating gaps that allow the stent to flex and articulate while maintaining cellular exclusion where the graft material is present. The segments can independently move relative to each other, enabling the device to navigate anatomical curves.
Solution Approach 2:
The graft covering is applied selectively to specific portions of the stent frame rather than uniformly across the entire device. This localized encapsulation provides cellular infiltration prevention only where clinically necessary, while leaving other portions of the stent exposed to maintain flexibility and articulation capability. The graft material is concentrated in regions requiring structural support and cell exclusion, while flexibility-critical regions remain uncovered.
2Reliability
If a stent graft uses monolithic encapsulation with ePTFE to prevent cellular infiltration, then cell infiltration is prevented, but the device becomes inflexible and prone to kinking
Solution Approach 1:
The continuous graft covering is segmented into discrete portions spaced along the stent frame. This segmentation prevents the formation of kinks by allowing the graft segments to move independently relative to each other during articulation. The gaps between segments act as hinge points that accommodate bending and flexing without creating stress concentrations that would lead to kinking.
Solution Approach 2:
The graft covering transitions from a static, rigid monolithic structure to a dynamic, articulated system where individual graft segments can move relative to each other. This dynamic configuration allows the graft to adapt its shape during device articulation and deployment, maintaining structural integrity while preventing kink formation through controlled segmental movement.
3Ease of manufacture
If traditional stent graft methods use adhesives or suturing for encapsulation, then the graft can be attached to the stent frame, but the process becomes labor-intensive and complex
Solution Approach 1:
The graft portions are designed to self-attach to the stent frame through inherent mechanical interlocking features rather than requiring external adhesives or suturing. The graft material includes integrated attachment mechanisms such as barbs, hooks, or interlocking geometries that engage with corresponding features on the stent frame during assembly, enabling attachment without additional fastening materials or complex procedures.
Solution Approach 2:
The attachment function is merged with the graft material structure itself rather than being a separate process. The graft portions are designed as integrated units that combine both the encapsulation function and the attachment mechanism in a single component, eliminating the need for separate adhesives, sutures, or fastening operations and simplifying the overall manufacturing process.
Data Source
AI summary
A stent device includes a first graft member, a second graft member and a stent frame defining a central axis. The frame has an abluminal surface engaged with the first graft member and a luminal surface engaged with the second graft member such that the first graft member and the second graft member encapsulates the stent frame along the length of the central axis. The stent frame includes a configuration where the stent frame is disposed on a curvature such that the abluminal surface has a radius of curvature of approximately 20 millimeters about a center of the curvature and the luminal surface defines a substantially constant effective cross-sectional area at any portion generally transverse to the central axis of the stent frame disposed about the curvature.