Hyperboloid Stent Graft Fixation Coupling for Torsion Stress
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Solution Overview
Problem
Existing branch vessel stent grafts face challenges in securely attaching to fenestrated stent grafts due to torsion and stress in the endovascular system, particularly at the junction of main and branch vessels, which can lead to misplacement and instability.
Innovation Solution
A hyperboloid or bell-shaped fixation coupling with self-expanding nitinol rings and a moveable joint design that securely seals within fenestrations, allowing for rotational and angular movement while reducing stress on the stent grafts, and providing tactile feedback for accurate placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a fixed rigid joint is used to connect branch stent graft to main vessel graft, then structural strength is improved, but adaptability to torsion and angular misalignment deteriorates
Solution Approach 1:
The joint transitions from a fixed rigid connection to a dynamic movable joint that allows rotational and angular movement. The movable joint includes a joint body with an internal cavity and a movable component that can rotate and pivot, enabling the joint to adapt to torsion and angular misalignment while maintaining structural integrity through self-adjustment during physiological movements.
Solution Approach 2:
The joint design incorporates variable geometric parameters including a hyperboloid or bell-shaped configuration with specific curvature radii and dimensional ratios. These parameter variations optimize both the strength of attachment and the range of motion, allowing the joint to maintain structural strength while accommodating torsional stresses and angular misalignment through its geometric design.
2Adaptability or versatility
If a movable joint design is used to allow rotational movement, then adaptability to torsion is improved, but structural stability deteriorates
Solution Approach 1:
Different regions of the joint have different functional properties: the joint body provides structural stability with its hyperboloid or bell-shaped configuration, while the movable component within the internal cavity provides rotational freedom. The sealing surface at the distal end ensures stable sealing, while the proximal connection maintains structural integrity. This local differentiation allows the joint to be stable where needed and movable where required.
Solution Approach 2:
The hyperboloid or bell-shaped configuration with curved surfaces provides both structural stability and rotational capability. The curved geometry distributes stresses evenly during rotational movement and maintains structural integrity under load, while the specific curvature radii and dimensional ratios optimize both stability and range of motion.
3Ease of operation
If self-expanding nitinol rings are used for sealing, then ease of deployment is improved, but manufacturing precision requirements worsen
Solution Approach 1:
The self-expanding nitinol rings utilize the material's superelasticity and shape memory properties, changing from a compressed delivery state to an expanded deployed state. The rings are designed with specific dimensional parameters including diameter, thickness, and wire diameter that enable reliable sealing while accommodating variations in fenestration geometry. The expansion ratio and final dimensions are carefully controlled to ensure sealing effectiveness without requiring extremely tight manufacturing tolerances.
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 fixation coupling ensures secure attachment and multi-directional movement of branch vessel stent grafts to fenestrated stent grafts, reducing stress and facilitating accurate deployment, thereby enhancing the stability and effectiveness of the stent graft system.
Implementation Method 1
The fixation coupling includes a distal ring, a proximal ring, and a hyperboloid area positioned between the rings. The rings are non-helical.
Data Source
Figure 1~4
Figure 5a~5b
Figure 5c~5d
AI summary
A small vessel stent graft (30; 62) with a fixation coupling (10; 50) that has a hyperboloid shape positioned at or near the proximal end of the graft (30; 62). The coupling (10; 50) may be deployed within the fenestration (42; 65) of a fenestrated graft (40; 60) to provide multi-directional movement without compromising the integrity of the sealing zone.