Stent Delivery System with Dynamic Constraint Mechanism
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Solution Overview
Problem
Conventional stent delivery systems face challenges such as difficulty in repositioning or removing self-expanding stents after deployment, inaccurate placement due to sheath obstruction, high force requirements for stent placement, and mechanical stress on the introducer, leading to issues like stent migration and uneven deployment.
Innovation Solution
A stent delivery system comprising an inner and outer elongate shaft with proximal and distal restraining members and biasing members that allow controlled deployment and recapture of the stent, enabling precise placement and repositioning by releasing tension to transition the stent between collapsed and expanded configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional outer sheath/inner catheter delivery device is used, then the stent can be delivered to the target location, but the device is difficult to reposition or remove and slow to operate
Solution Approach 1:
The delivery device employs dynamic constraints where the stent is held compressed by the outer sheath during delivery, then rapidly deployed by proximal retraction of the sheath. The system transitions from a constrained delivery state to an unconstrained deployed state, enabling quick repositioning before final deployment. This dynamic constraint mechanism allows the physician to control stent expansion timing and location precisely.
2Measurement precision
If the outer sheath is proximally withdrawn to partially deploy the stent for positioning verification, then the stent position can be checked, but the sheath cannot reconstrain the stent once fully deployed
Solution Approach 1:
The system allows dynamic transition between constrained and unconstrained states. During partial deployment for positioning verification, the outer sheath can be retracted to expose the stent for imaging verification. If repositioning is needed, the sheath can be pushed back over the stent to reconstrain it in the compressed state, allowing repeated positioning checks before final deployment.
3Productivity
If the physician manually retracts the outer sheath, then the stent can be deployed, but controlled movement is difficult to achieve leading to uneven or inadvertent movement
Solution Approach 1:
The system introduces an intermediary mechanism where the inner catheter serves as a guide for controlled sheath retraction. The outer sheath is pulled over the inner catheter, which provides a stable reference and allows the physician to control the retraction speed and uniformity. This intermediary structure ensures even deployment of the stent along its entire length without inadvertent movement.
4Productivity
If the distal portion of the stent is deployed first during sheath retraction, then the stent can be released, but accurate placement of the proximal portion becomes difficult
Solution Approach 1:
The system performs preliminary positioning of the entire stent assembly within the outer sheath before deployment begins. The stent is pre-positioned relative to the sheath and inner catheter, ensuring that when retraction occurs, both distal and proximal portions deploy simultaneously and uniformly. This preliminary alignment prevents the distal-first deployment problem and ensures accurate proximal placement.
5Object-affected harmful factors
If the outer sheath covers the stent during delivery, then the stent is protected, but direct visualization of the stent is prevented making accurate placement difficult
Solution Approach 1:
The outer sheath is designed as a thin, radiolucent or transparent flexible structure that allows imaging modalities (fluoroscopy, ultrasound, or optical imaging) to visualize the stent and surrounding anatomy during delivery. The sheath material permits passage of imaging signals while still providing mechanical protection and constraint of the stent during navigation to the target site.
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 system enhances control and accuracy in stent placement, reduces the risk of premature deployment, and allows for smoother, quicker deployment and recapture of the stent, addressing the limitations of conventional sheathed systems.
Implementation Method 1
Self-expanding stents are often made of a wire or mesh material that can elastically contract and expand
Implementation Method 2
A tensioning member may be attached to the stent and the inner elongate shaft. Movement of the inner elongate shaft relative to the outer elongate shaft in a first direction may release tension to the tensioning member to move the stent to the expanded configuration
Data Source
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AI summary
A stent delivery system is provided with an inner elongate shaft having a proximal portion and a distal portion and an outer elongate shaft having a lumen extending at least partially therethrough, wherein the proximal portion of the inner elongate shaft is at least partially movably disposed within the lumen. The system also includes a stent positionable about the inner elongate shaft having collapsed and expanded configurations. The system includes a proximal restraining member removably engaged with the outer elongate shaft and attached the stent, and a distal restraining member removably engaged with the inner elongate shaft and attached to the stent. The system also has a proximal biasing member operatively engaged with a distal portion of the outer elongate shaft, a distal biasing member operatively engaged with the distal portion of the inner elongate shaft, and an outer tube with a lumen movably disposed over the inner elongate shaft.