Wire-Controlled Sheath Withdrawal for Stent Deployment
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Solution Overview
Problem
The precise placement of intraluminal medical devices, such as self-expanding stents, is hindered by deflection during deployment due to frictional forces between the medical device and the outer sheath, making it difficult for physicians to accurately control the deployment process.
Innovation Solution
A delivery system featuring an inner catheter with a stop surface and a restraining sheath surrounded by wires that are adhered to the sheath and extend to a deployment handle, allowing for controlled withdrawal of the sheath to deploy the stent by pulling the wires, reducing friction and improving control over the deployment process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the outer sheath is withdrawn by pulling it proximally relative to the inner catheter, then the medical device is released and self-expands, but frictional forces between the medical device and outer sheath cause the outer sheath to stretch and require high withdrawal force
Solution Approach 1:
The delivery system is divided into separate functional components: an inner catheter for advancing the device, an outer sheath for restraining and deploying the device, and a wire for controlling sheath withdrawal. This segmentation allows each component to perform its specific function independently, improving control while reducing the force needed for sheath withdrawal.
Solution Approach 2:
A wire is introduced as an intermediary element between the deployment handle and the outer sheath. The wire is adhered to the outer sheath and extends to the deployment handle, allowing the physician to control sheath withdrawal through the wire rather than directly pulling the sheath, thereby reducing frictional forces and improving control precision.
2Reliability
If the medical device presses outward against the inner surface of the outer sheath prior to deployment, then the device is restrained in compressed state, but frictional forces cause deflection of the delivery system during deployment
Solution Approach 1:
The wire serves as an intermediary that transmits force from the deployment handle to the outer sheath without requiring direct contact between the medical device and the sheath during withdrawal. This intermediary mechanism reduces frictional forces that would otherwise cause delivery system deflection and placement imprecision.
Solution Approach 2:
The direct mechanical contact between the medical device and outer sheath is replaced by a wire-based control system. Instead of relying solely on friction-based restraint, the wire provides controlled tension to withdraw the sheath, reducing mechanical interference and improving placement precision.
3Ease of operation
If the outer sheath is made to be withdrawable by pulling, then the medical device can be deployed, but the frictional force between the medical device and outer sheath makes it difficult to control deployment accurately
Solution Approach 1:
The wire acts as a mediator between the deployment handle and the outer sheath, allowing for precise control of sheath withdrawal. By controlling the wire tension rather than directly manipulating the sheath, the physician can achieve more accurate deployment control while reducing the effect of frictional forces.
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 solution enhances the accuracy and control of stent deployment by minimizing frictional forces, reducing the force required to withdraw the sheath, and allowing for precise placement of self-expanding medical devices.
Implementation Method 1
The medical device is deployed by pulling on the wire which causes the restraining sheath to withdraw proximally from the medical device
Implementation Method 2
the frictional force between the medical device and the outer sheath causes the outer sheath to be in tension
Implementation Method 3
the medical device is typically prevented from moving proximally with the outer sheath by a stop attached to the inner catheter
Implementation Method 4
self-expanding medical devices, including stents, are made from an elastic structure that may be compressed into a low profile state
Implementation Method 5
the self-expanding medical device is released and self-expands like a spring until it contacts a tissue wall
Data Source
AI summary
A delivery system is provided for self-expanding medical devices, such as stents. The delivery system has a restraining sheath that maintains the stent in a compressed state prior to deployment. The restraining sheath terminates distally from the deployment handle, and a wire connects the restraining sheath to the deployment handle. The restraining sheath is withdrawn from the stent to deploy the stent by pulling the wires proximally at the deployment handle.