Inner Catheter Arrangement for Self-Expanding Stent Delivery
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Solution Overview
Problem
The precise placement of intraluminal medical devices, such as self-expanding stents, is compromised due to deflection of the delivery system during deployment, caused by frictional forces between the medical device and the outer sheath, leading to potential misplacement and unpredictable release locations within the patient's body.
Innovation Solution
The delivery system incorporates a first inner catheter with a closed coil wire structure and a polymer outer layer, along with a second inner catheter that extends past a stop surface, both unattached along the length inserted into the patient's body, to minimize frictional interference and facilitate precise placement by allowing the outer sheath to slide proximally relative to the stent, enabling controlled expansion and reduced buckling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the outer sheath is withdrawn to deploy the self-expanding medical device, then the medical device is released and expands at the treatment site, but frictional forces cause deflection and buckling of the inner catheter leading to imprecise placement
Solution Approach 1:
The inner catheter is divided into two separate unattached catheters (first and second inner catheters) that can move independently relative to each other and the outer sheath. This segmentation allows each catheter to respond differently to frictional forces during withdrawal, reducing buckling and improving placement precision.
Solution Approach 2:
The delivery system is designed to allow dynamic movement and relative motion between the outer sheath and the inner catheters during withdrawal. The unattached configuration enables the catheters to flex and adjust dynamically, preventing buckling while maintaining control over device placement.
2Stability of the object's composition
If the inner catheter is made rigid to prevent buckling, then structural stability is improved, but frictional interference increases and prevents smooth withdrawal of the outer sheath
Solution Approach 1:
Dividing the inner catheter into two separate unattached catheters allows each segment to maintain adequate structural stability while reducing overall frictional interference. The segmented structure can flex independently, enabling smooth sheath withdrawal without requiring excessive rigidity.
Solution Approach 2:
The system changes the structural parameters of the catheters by making them unattached and flexible rather than rigid. This parameter change reduces friction during withdrawal while maintaining sufficient stability through the distributed structure of multiple catheters.
3Ease of operation
If the outer sheath is pulled proximally to withdraw it after deployment, then the sheath is removed from the body, but the inner catheter contracts and buckles causing distal movement of the medical device
Solution Approach 1:
The two unattached inner catheters are designed to move independently during proximal withdrawal of the outer sheath. This segmentation prevents synchronized buckling and contraction that would otherwise cause distal movement of the deployed medical device, maintaining placement accuracy.
Solution Approach 2:
The dynamic, unattached configuration of the inner catheters allows them to adjust their positions independently during sheath withdrawal. This dynamic behavior prevents the contraction and buckling that would compromise device placement accuracy while still enabling smooth sheath removal.
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
This design enhances the accuracy of medical device placement by reducing frictional forces and buckling, allowing for predictable and precise deployment of self-expanding stents, minimizing the risk of misplacement and ensuring effective expansion against the vessel wall.
Implementation Method 1
self-expanding medical devices, including stents, are made from an elastic structure that may be compressed into a low profile state that can be passed through vessels in a patient with minimal trauma. Once at the desired treatment site, the self-expanding medical device is released and self-expands like a spring until it contacts a tissue wall which prevents further expansion.
Implementation Method 2
When the outer sheath is withdrawn, the outward pressure exerted by the medical device creates friction between the medical device and the outer sheath. Since the medical device is typically prevented from moving proximally with the outer sheath by a stop attached to the inner catheter, the frictional force between the medical device and the outer sheath causes the outer sheath to be in tension and the inner catheter to be in compression.
Data Source
AI summary
A delivery system for a self-expanding medical device is provided. The delivery system includes an outer sheath that radially restrains the medical device. First and second inner catheters are disposed within the outer sheath. The first inner catheter is a composite structure with a closed coil wire covered by a polymer outer layer. The second inner catheter is disposed within the closed coil wire but is not attached to the closed coil wire.