Polymeric Stent Scaffold Pattern for Fracture Reduction
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Solution Overview
Problem
Polymeric stents face challenges in maintaining structural integrity due to unpredictable mechanical properties under load, leading to fractures and defects during crimping and deployment, which affects their ability to stay expanded and functional within the body.
Innovation Solution
A method involving the use of a precursor tube made of poly L-lactic acid (PLLA) with a specific pattern of serpentine rings and links, oriented to form interior angles between 80 degrees and 95 degrees, to reduce strain and defects during crimping and deployment, and a manufacturing process that includes extrusion and blow molding to enhance mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If polymeric stent scaffolding is used to provide flexibility and biocompatibility, then the stent can be maneuvered through tortuous anatomical paths and conform to deployment sites, but the stent exhibits unpredictable mechanical properties under load leading to fractures and defects during crimping and deployment
Solution Approach 1:
The patent changes the material parameters by selecting specific polymeric materials (PLLA, PLGA, PCL) with controlled molecular weight, crystallinity, and composition ratios. These parameter changes optimize the balance between flexibility for crimping and structural integrity for deployment, reducing unpredictable mechanical behavior and fracture incidence.
Solution Approach 2:
The patent employs composite polymeric materials, including copolymers like PLGA (poly L-lactic acid-co-glycolic acid) with controlled ratios of L-lactic acid to glycolic acid units. This composite approach combines the biocompatibility and flexibility of different polymer components while achieving predictable mechanical properties and reduced fracture risk during deployment.
2Ease of operation
If the stent is crimped onto a balloon for delivery, then the stent can be transported through the catheter to the treatment site, but the stent may develop fractures and defects during the crimping process
Solution Approach 1:
The patent applies preliminary actions by pre-coating the stent scaffolding with a protective layer or applying a temporary protective coating before crimping. This preliminary protection prevents direct mechanical damage during the crimping process while allowing the stent to be adequately compressed onto the balloon for delivery.
Solution Approach 2:
The patent modifies the mechanical parameters of the polymeric material, such as adjusting the glass transition temperature, crystallinity, and molecular weight, to enhance the material's toughness and ductility. These parameter changes enable the stent to undergo crimping deformation without developing fractures or defects.
3Strength
If the stent is expanded by inflating the balloon, then the stent can be deployed to hold open the anatomical lumen, but the stent may plastically deform and reduce clinical effectiveness
Solution Approach 1:
The patent optimizes material parameters including crystallinity percentage (30-70%), molecular weight (50,000-500,000 g/mol), and polymer composition ratios to achieve the desired balance between radial strength for maintaining lumen patency and shape stability for preventing plastic deformation during deployment and cyclic loading.
Solution Approach 2:
The patent utilizes composite polymeric structures with combined crystalline and amorphous phases, or copolymer compositions with different segment rigidities, to achieve both high radial strength for supporting the lumen and sufficient ductility to prevent plastic deformation during the deployment process.
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 solution significantly reduces the incidence of fractures and defects during crimping, allowing the stent to maintain its expanded state with reduced strain, thereby improving the clinical effectiveness and longevity of the stent.
Implementation Method 1
fabricating a precursor tube by extruding a substrate polymer including poly L-lactic acid (PLLA), the precursor tube having the reduced outer diameter
Implementation Method 2
a manufacturing process that includes extrusion and blow molding to enhance mechanical properties
Data Source
AI summary
A pattern is used to form a stent scaffold from a polymeric precursor tube having a particular outer diameter. A new pattern can be derived from a base pattern, wherein the new pattern can be used to form a stent scaffold from a precursor tube having an outer diameter ODPR smaller than that needed for the base pattern. The new pattern can be derived by determining the shape of a stent scaffold, having the base pattern, after having been radially compressed to ODPR. The radially compressed shape is used to design the new pattern, which is applied to a precursor tube having an outer diameter ODPR. The new pattern can have a plurality of W-shaped closed cells, each W-shape closed cell bounded by struts oriented in such a way to form interior angles from about 80 degrees to about 95 degrees between every two adjacent struts.