Guidewire Torque Transmissibility via Segmented Coil Design
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Solution Overview
Problem
Conventional guidewires face challenges in achieving high rotational and pushing torque transmissibility while maintaining restorability, especially when navigating narrow stenosis, as increasing core shaft stiffness leads to plastic deformation and reduced flexibility.
Innovation Solution
A guidewire design featuring a core shaft with a tapered outer coil and an inner coil with varying diameters and strand thicknesses, along with strategic joint placements and coil configurations, to enhance torque transmissibility and flexibility, allowing for effective navigation of narrow stenosis without plastic deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the core shaft diameter is increased to increase stiffness and torque transmissibility, then rotational torque transmissibility and pushing torque transmissibility are improved, but restorability deteriorates and the tip portion may undergo plastic deformation
Solution Approach 1:
The guidewire is divided into multiple functional segments: a proximal core shaft portion with larger diameter for torque transmission, and a distal tip portion with smaller diameter for flexibility and restorability. The coil structure is segmented into multiple turns with varying pitch to create different stiffness characteristics in different regions, allowing the proximal end to be stiff while the distal end remains flexible and restorable.
Solution Approach 2:
Different portions of the guidewire are given different mechanical properties through variable diameter design. The proximal core shaft has larger diameter and higher stiffness for torque transmission, while the distal tip portion has smaller diameter and lower stiffness for flexibility. The coil pitch is also varied locally to optimize both torque transmissibility and restorability in different regions.
2Strength
If the core shaft diameter is increased to increase stiffness and torque transmissibility, then torque transmissibility is improved, but flexibility deteriorates making insertion into narrow stenosis difficult
Solution Approach 1:
The guidewire structure is segmented into a proximal stiff portion and a distal flexible portion. The coil structure is divided into multiple turns with different pitch characteristics, allowing the proximal end to provide stiffness for torque transmission while the distal end maintains flexibility for navigation through narrow stenosis.
Solution Approach 2:
The guidewire exhibits spatially varying mechanical properties: the proximal region has larger diameter and higher stiffness for torque transmission, while the distal tip portion has smaller diameter and lower stiffness for flexibility and ease of insertion into narrow lesions.
3Strength
If the core shaft is made entirely thick to increase stiffness and torque transmissibility, then rotational and pushing torque transmissibility are improved, but the tip portion becomes prone to plastic deformation in narrow lesion locations
Solution Approach 1:
The guidewire is segmented into a proximal core shaft portion and a distal tip portion with different diameter characteristics. The coil structure is segmented into multiple turns with varying pitch, creating a gradient of stiffness that prevents the tip portion from undergoing plastic deformation while maintaining overall torque transmissibility.
Solution Approach 2:
The tip portion is designed with smaller diameter and optimized coil characteristics to reduce stress concentration and prevent plastic deformation, while the proximal portion maintains larger diameter for torque transmission. This local quality differentiation eliminates the harmful effect of plastic deformation at the tip.
Data Source
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AI summary
A guidewire (10) having high rotational torque transmissibility and high pushing torque transmissibility and having favorable restorability is provided. The guidewire has an outer coil (60) having a tapered coil portion constituted by at least one strand wound to decrease an outer diameter toward a front end of a core shaft and an inner coil (50,150,250) arranged inside the outer coil. An outer diameter on a front side of the inner coil arranged on a front side of the tapered coil portion is smaller than an outer diameter on a rear side of the inner coil.