Capsule Plug Inversion for Stent Graft Introducer Retrieval
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Solution Overview
Problem
Existing capsule assemblies for stent graft introducers face challenges in maintaining their position during retrieval, particularly in winding and pulsating aortas, leading to potential dislodgment of the stent graft from the lumen wall due to the distally facing opening of the capsule.
Innovation Solution
A capsule assembly with a capsule plug that includes a tip portion, an abutment surface, and a tail portion, allowing the capsule to move from a first position surrounding an opening to a second position where the distal end is positioned proximally with respect to the abutment surface, providing resistance and facilitating smooth retraction through the stent graft and vasculature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the capsule has a distally facing opening with an edge surrounding it, then the capsule can be removed from the exposed stent after deployment, but the edge can engage with stents of the deployed stent graft and potentially cause problems by dislodging the stent graft from its position on the wall of the lumen
Solution Approach 1:
The capsule plug is inverted relative to conventional designs: the tip portion (normally distal) is positioned proximally within the capsule, and the tail portion (normally proximal) extends distally. This inversion allows the rounded tip to lead during retrieval, preventing engagement with stent struts while the tail portion provides stabilization through engagement with the capsule's internal landing zone.
Solution Approach 2:
The capsule plug acts as an intermediary element between the capsule and the stent graft during retrieval. By positioning the plug's tip portion within the capsule cavity and its tail portion extending beyond, it mediates the interaction between the capsule wall and stent struts, preventing direct engagement that could cause dislodgment while facilitating smooth withdrawal.
2Reliability
If the capsule plug remains in its correct position during retrieval through the aorta, then stable retrieval is achieved, but the capsule plug must resist movement through winding and pulsating vasculature
Solution Approach 1:
The capsule plug design incorporates dynamic adaptation: the tip portion can diverge to navigate tortuous vasculature, while the tail portion dynamically engages with the capsule's landing zone to maintain position stability. The plug transitions from a constrained state during insertion to a more flexible state during retrieval, adapting to vascular conditions while maintaining reliable positioning.
Solution Approach 2:
The capsule plug utilizes parameter changes in its geometry: the tip portion diameter varies along its length (diverging then converging), and the tail portion has specific dimensional relationships with the landing zone. These parameter variations allow the plug to navigate winding vasculature while maintaining stable engagement with the capsule during pulsating blood flow conditions.
3Ease of operation
If the tip portion diverges to a maximum diameter, then smooth transition and retraction is facilitated, but the capsule plug size increases
Solution Approach 1:
The capsule plug is segmented into distinct functional portions: a tip portion with diverging geometry for smooth transition, an intermediate portion for size reduction, and a tail portion for stabilization. This segmentation allows the plug to have a larger maximum diameter where needed for smooth retraction while maintaining a smaller overall profile through the intermediate portion, optimizing both ease of operation and space constraints.
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 capsule assembly ensures stable retrieval of the introducer without dislodging the stent graft, even through torturous vasculature, by providing a smooth transition and resistance mechanism, preventing premature withdrawal of the capsule plug from the capsule.
Implementation Method 1
the distal end of the capsule wall has a terminal internal diameter that is resiliently expandable to allow the tip portion to move distally from the first position to the second position
Implementation Method 2
movement of the tip portion into the capsule is resisted by abutment between the distal end of the capsule wall and the abutment surface
Implementation Method 3
a tail portion having an external surface engageable with an inside surface of the capsule wall
Data Source
AI summary
A capsule assembly for an endograft introducer is disclosed. The assembly comprises: a capsule and a capsule plug. The capsule has a cavity for receiving an end of a stent graft and a capsule wall terminating in a distal end. The capsule plug comprises: a tip portion having a lead-in surface and an abutment surface; and a tail portion having an external surface engageable with an inside surface of the capsule wall. The capsule is slideably movable with respect to the capsule plug from a first position in which the distal end of the capsule wall surrounds an opening into the cavity to a second position in which the distal end of the capsule wall is positioned proximally with respect to the abutment surface, whereby movement of the tip portion into the capsule is resisted by abutment between the distal end of the capsule wall and the abutment surface.