Catheter Retention Elements Using Shape Memory Alloy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional catheter devices face challenges in maintaining a firm grip of self-expanding tubular implants during deployment, leading to potential delivery system failure due to varying implant weights and dimensions, with existing solutions requiring higher deployment forces and risking implant damage.
Innovation Solution
The catheter device incorporates shape memory alloy retention elements that protrude radially to engage the implant, providing consistent friction and retention force across a range of implant weights and dimensions, preventing proximal or distal movement, and utilizing nitinol for enhanced reliability and space efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicone sleeve with fine metal wire braid is used to improve grip, then implant retention is improved, but deployment force increases and device complexity increases
Solution Approach 1:
The inner catheter distal end is segmented into multiple independent retention elements (flaps, bars, or spikes) that can individually engage with the implant. This segmentation allows distributed contact points along the implant length, improving retention without requiring excessive radial compression force, thus resolving the contradiction between reliable implant retention and excessive deployment force.
Solution Approach 2:
Instead of using a flexible silicone sleeve that compresses radially, the invention inverts the approach by using rigid retention elements that protrude radially outward to engage the implant. This inversion provides effective grip through mechanical interlocking rather than radial compression, reducing the deployment force required while maintaining reliable retention.
2Reliability
If retention elements are made from stiff material to provide strong grip, then implant retention is improved, but the ability to accommodate implant dimension variations deteriorates
Solution Approach 1:
The retention elements are designed with flexible hinges connecting them to the inner catheter wall, allowing dynamic adjustment of their position and angle. This flexibility enables the rigid retention elements to adapt to varying implant dimensions and weights while maintaining strong engagement, thus resolving the contradiction between strong grip and adaptability to dimensional variations.
Solution Approach 2:
The retention elements utilize shape memory alloy material that changes its physical state or dimensions in response to temperature changes or mechanical deformation. This parameter change capability allows the retention elements to maintain optimal engagement forces across different implant sizes and weights, providing both strong retention and adaptability simultaneously.
3Reliability
If radial compression is increased to improve grip on lightweight implants, then implant retention is improved, but delivery system joint strength is exceeded leading to failure
Solution Approach 1:
By segmenting the retention mechanism into multiple distributed elements along the implant length, the total retention force is spread across multiple contact points rather than concentrated at a single compression interface. This reduces the radial compression force required at each point, preventing delivery system joint failure while maintaining reliable implant retention.
Solution Approach 2:
The invention inverts the conventional approach by using radially protruding rigid retention elements instead of radially compressing flexible sleeves. This provides effective grip through mechanical engagement rather than high radial compression, thereby maintaining implant retention without exceeding the strength limits of delivery system joints.
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 ensures reliable deployment of self-expanding implants by maintaining constant radial stress and friction, reducing the risk of delivery system failure and implant damage, while accommodating varying dimensions and weights, and facilitating deployment in tortuous lumens.
Implementation Method 1
the first plurality of implant retention elements are configured to utilise a shape memory effect to assume a radially outwardly protruding configuration to engage the radially inward facing surface of the implant prior to the withdrawal of the sheath
Implementation Method 2
utilizing nitinol for enhanced reliability and space efficiency
Data Source
AI summary
There is provided a catheter device for transluminally delivering a self-expanding tubular implant to a site in a body, the device comprising:an inner catheter comprising a cylindrical distal end component with a wall, wherein the cylindrical distal end component is arranged, in use, to be received within the lumen of the implant; anda sheath, coaxial with the inner catheter, wherein the sheath is arranged to sheath the implant until, in use, the sheath is withdrawn proximally, relative to the implant and the inner catheter, to release (deploy) the implant at the site,wherein the cylindrical distal end component includes a first plurality of implant retention elements, which, during withdrawal of the sheath protrude radially outwardly from the cylindrical distal end component to engage a radially inward facing surface of the implant to restrain the implant from being carried by the sheath proximally, relative to the cylindrical distal end component, characterized in that: the first plurality of implant retention elements are formed from a portion of the wall of the cylindrical distal end component, and in that: the first plurality of implant retention elements are configured to utilise a shape memory effect to assume a radially outwardly protruding configuration to engage the radially inward facing surface of the implant prior to the withdrawal of the sheath.