Stent Delivery Pusher Ratchet Mechanism
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Solution Overview
Problem
Current stent delivery systems face challenges in efficiently deploying stents across occlusions in body vessels or non-body structures like polymer tubes, requiring improved mechanisms for stent advancement and expansion.
Innovation Solution
A stent delivery system comprising a stent, a stent delivery catheter, and a handle, where the stent has a radially reduced and expanded configuration, and the catheter includes a stent-engaging member with a ratchet and stem mechanism to facilitate distal advancement and proximal retraction, allowing precise engagement and deployment of the stent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a stent delivery system uses a simple push mechanism, then the device complexity is reduced, but the precision of stent engagement and deployment control deteriorates
Solution Approach 1:
The pusher assembly is segmented into distinct functional components: a pusher member for axial movement, a ratchet mechanism for unidirectional force transmission, and a stem for structural support. This segmentation allows each component to perform its specific function efficiently while maintaining overall system precision without excessive complexity.
Solution Approach 2:
The ratchet mechanism acts as an intermediary between the pusher member and the stent. It translates the axial pushing motion into controlled unidirectional force application, ensuring precise engagement with the stent's radial structure while preventing backward movement, thus achieving precise deployment control.
2Manufacturing precision
If the stent-engaging member uses a complex ratchet mechanism, then the precision of stent advancement is improved, but the device complexity increases
Solution Approach 1:
The ratchet mechanism is designed to engage and disengage automatically based on the axial movement of the pusher member. When the pusher advances, the ratchet engages with the stent's radial structure to prevent retraction. When the pusher retracts, the ratchet naturally disengages without requiring additional actuation mechanisms, achieving precise control through self-service operation.
Solution Approach 2:
The ratchet mechanism uses simple geometric features (radial projections on the stent, corresponding engagement surfaces on the pusher) rather than complex mechanical components. This simplified design reduces device complexity while maintaining precision, treating the engagement mechanism as a single-use feature for each deployment event.
3Reliability
If the pusher assembly uses a ratchet mechanism with radial structure engagement, then the reliability of stent deployment is improved, but the difficulty of navigating through body vessels increases
Solution Approach 1:
The pusher member is designed with flexible or adjustable sections that allow it to adapt to the curved geometry of body vessels during navigation. The ratchet mechanism engages only during the deployment phase when axial force is applied, while allowing the pusher to flex during navigation, thus maintaining reliability while improving ease of operation.
Solution Approach 2:
The pusher assembly incorporates flexible components that can bend and conform to the vessel's anatomy during insertion and navigation. These flexible sections maintain their structural integrity when axial force is applied for deployment, ensuring reliable ratchet engagement while facilitating easy navigation through tortuous vessels.
Data Source
AI summary
A pusher assembly for a stent delivery device includes a distal end of an elongate member and a stent-engaging member having proximal and distal ends. The proximal end of the stent-engaging member is mechanically coupled to the distal end of the inner member by a connector, or the proximal end of the stent-engaging member is at least partially inside the distal end of the elongate inner member. The stent-engaging member includes a portion that radially outwardly extends towards the distal end of the stent-engaging member, or the stent-engaging member includes a portion that radially outwardly extends towards the distal end of the stent-engaging member. The stent-engaging member is configured to move a stent when distally advanced and configured to not move a stent when proximally retracted. A stent delivery device includes an elongate outer member, an elongate inner member coaxially positioned within the outer member, and the pusher assembly.