Stent Retaining Interlock for Controlled Deployment
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Solution Overview
Problem
Existing stent delivery systems face challenges with premature deployment and difficulty in adjusting or re-sheathing self-expanding stents due to their elastic characteristics, leading to compromised control over stent placement and positioning.
Innovation Solution
A stent delivery system equipped with an interlock configuration that constrains relative axial movement between the stent and inner tube until the outer sheath is fully retracted, featuring interlock structures that prevent premature expansion and allow controlled deployment and re-sheathing by using a combination of interlock structures and radiopaque markers for precise positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the outer sheath is retracted to expose the stent for deployment, then the stent can expand to its functional state, but the stent may prematurely deploy and be propelled distally beyond the desired deployment site
Solution Approach 1:
The interlock structure (comprising interlocking elements on the stent and corresponding receptacles on the inner tube) is designed to preemptively counteract the premature deployment force. The interlocking mechanism creates a mechanical constraint that opposes any premature expansion or distal propulsion of the stent during sheath retraction, thereby preventing the harmful effect before it occurs.
Solution Approach 2:
The stent is pre-mounted on the inner tube in a compressed state with the interlock structure engaged before delivery. This preliminary configuration ensures that the stent remains constrained during navigation and sheath retraction, and only deploys when intentionally released at the target site by fully retracting the outer sheath.
2Adaptability or versatility
If the stent is allowed to expand freely upon exposure, then the stent can perform its supporting function, but adjustments to stent placement become difficult once partially unsheathed
Solution Approach 1:
The interlock structure is designed with dynamic characteristics that allow it to transition from a constrained state during delivery to a released state upon full sheath retraction. The interlocking elements and receptacles are configured to maintain engagement during positioning adjustments, enabling the operator to re-sheath and re-position the stent as needed before final deployment.
Solution Approach 2:
The system utilizes changes in the mechanical state of the interlock structure corresponding to sheath position. When the outer sheath is partially retracted, the interlock remains engaged allowing adjustments; when fully retracted, the interlock releases allowing expansion. This parameter change enables both adjustability and controlled deployment.
3Length of moving object
If the stent is mounted on the delivery system in a compressed state, then it can be delivered through the body lumen, but the elastic characteristics of self-expanding stents cause them to force themselves out of the sheath
Solution Approach 1:
The interlock structure is specifically designed to counteract the elastic expansion force of self-expanding stents during delivery. The interlocking elements engage with the receptacles to create a mechanical constraint that opposes the stent's natural tendency to expand and propel itself distally, allowing safe delivery in compressed state.
Solution Approach 2:
The inner tube with its interlock structure serves as an intermediary mechanism between the compressed stent and the delivery system. This intermediary structure provides the necessary mechanical constraint to hold the stent in place against its elastic expansion force, while still allowing controlled release when needed.
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 provides improved control over stent deployment and positioning, preventing premature release and allowing for accurate placement and adjustment, ensuring the stent remains securely attached to the delivery system until fully expanded and allowing for re-sheathing post-deployment.
Implementation Method 1
Other self-expanding stents are made of so-called shape-memory metals such as nitinol. Such shape-memory stents experience a phase change at the elevated temperature of the human body. The phase change results in expansion from a collapsed state to an enlarged state.
Implementation Method 2
The stent includes a first interlock structure. The catheter includes an elongated member having a second interlock structure displaceably arranged about an outer surface thereof for engaging the first interlock structure of the stent.
Data Source
AI summary
A stent delivery system includes an expandable stent, a catheter, and a sheath. The expandable stent includes proximal and distal ends, and a first interlock structure. The catheter includes an elongated member having a second interlock structure displaceably arranged about an outer surface thereof for engaging the first interlock structure of the stent. The sheath is mounted on the elongated member and is positionable in a transport position in which the sheath covers the stent mounted on the elongated member and a deploy position in which the stent is exposed.