Tapered Pusher Sheath for Stent Deployment Kinking
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Solution Overview
Problem
Conventional deployment devices for stents and stent grafts often kink at the junction between the flexible guidewire catheter and the rigid pusher sheath, leading to device failure when navigating tortuous vessel paths, resulting in aborted procedures and patient trauma.
Innovation Solution
A pusher member with a reduced outer diameter section that tapers towards the distal end, maintaining longitudinal stiffness while increasing flexibility, reduces the likelihood of kinking and facilitates navigation through tortuous paths by providing a gradual transition in stiffness from the distal to the proximal end.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the pusher sheath is made significantly stiffer than the guidewire catheter to provide pushing force, then the pushing capability is improved, but the device becomes prone to kinking at the junction when navigating tortuous vessel paths
Solution Approach 1:
The pusher sheath incorporates a tapered distal section with reduced wall thickness compared to the proximal section. This creates a gradient in mechanical properties where the distal end is more flexible to navigate tortuous paths, while the proximal end remains stiff to provide adequate pushing force. The wall thickness transitions gradually from thinner at the distal end to thicker at the proximal end, optimizing both flexibility and structural integrity in different regions of the same component.
Solution Approach 2:
The pusher sheath is divided into distinct functional zones: a tapered distal section with reduced stiffness for navigation, and a proximal section with full stiffness for force transmission. This segmentation allows each portion to perform its specific function optimally without compromising the other, resolving the contradiction between needing both flexibility and rigidity in the same device.
2Adaptability or versatility
If the guidewire catheter is made flexible to follow tortuous vessel paths, then the ability to navigate complex anatomy is improved, but the device lacks the stiffness to provide adequate pushing force at the deployment site
Solution Approach 1:
The tapered distal section of the pusher sheath acts as an intermediary element between the flexible guidewire catheter and the stiff proximal pusher section. This intermediate zone with graduated stiffness facilitates smooth stress transfer and reduces the abrupt transition that causes kinking, while still allowing the overall system to navigate tortuous paths effectively.
3Force
If the pusher sheath is made uniformly rigid throughout to maintain pushing force, then the force transmission is improved, but the device cannot accommodate tortuous vessel paths without kinking
Solution Approach 1:
Rather than uniform rigidity, the pusher sheath employs spatially varying mechanical properties with the tapered distal section having reduced wall thickness for flexibility, while the proximal section maintains full thickness for force transmission. This local differentiation of mechanical properties resolves the contradiction between force transmission and adaptability to tortuous paths.
Data Source
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AI summary
A stent or stent-graft deployment device and in particular a pusher member for such a device are disclosed. The pusher member (62) is provided with a reduced outer diameter section (64) and a pusher head (60). The reduced outer diameter section (64) reduces the thickness of the wall of the pusher member (62), with the result that the rigidity of the pusher member (62) is reduced at its distal end. This reduction in rigidity reduces the transition in flexibility between a guidewire catheter (24) extending through and beyond an inner channel of the pusher member (62) and the distal end of the pusher member (62). Thus, there is a gradual change in rigidities at the junction between these two components, which can reduce the possibility of kinking.