Variable Stiffness Steering Spine for Catheters

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Solution Overview

Problem

Existing catheter designs face challenges in providing uniform flexibility and torsional rigidity, leading to irregular bend radii that can cause light loss in fiber optics and increased risk of damage, while also being difficult to manufacture and maneuver effectively.

Innovation Solution

A high-torque catheter with a deflectable tip section featuring a tapered steering spine of variable flexibility, where the flexibility increases from the proximal end to the distal end, tailored to compensate for frictional losses and maintain a uniform bend radius, enhancing torsional rigidity and flexibility without compromising internal components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a continuous spine portion is used to provide torsional rigidity, then torque transmission is improved, but the minimum bend radius is limited and flexibility is reduced

Engineering Contradiction:

Improvetorsional rigidityVSAvoidflexibility

Core Design Contradiction:

StrengthVSEase of operation

Solution Approach 1:

The catheter shaft is divided into multiple discrete segments (first shaft segment, second shaft segment, third shaft segment) with different stiffness characteristics. The first segment has high torsional rigidity for torque transmission, while the second and third segments have progressively lower stiffness to enable flexibility and small bend radii at the distal end.

Inventive Principle:

Principle #1Segmentation

2Ease of operation

If variable stiffness is increased at the distal end to improve flexibility, then ease of navigation is improved, but uniformity of bend radius is compromised

Engineering Contradiction:

ImproveflexibilityVSAvoiduniform bend radius

Core Design Contradiction:

Ease of operationVSStability of the object's composition

Solution Approach 1:

Each shaft segment is designed with specific local properties: the first segment has high torsional rigidity with constant cross-section for torque transmission, while the second and third segments have progressively lower stiffness. The second segment features an asymmetric cross-section with a flattened side to control bending behavior and achieve uniform bend radius despite varying flexibility.

Inventive Principle:

Principle #3Local quality

3Adaptability or versatility

If the catheter is made more flexible to navigate tortuous pathways, then adaptability is improved, but torsional rigidity and torque transmission are reduced

Engineering Contradiction:

Improvenavigation capabilityVSAvoidtorque transmission

Core Design Contradiction:

Adaptability or versatilityVSStrength

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

4Ease of manufacture

If uniform flexibility is maintained along the catheter length, then manufacturing simplicity is improved, but frictional losses cause non-uniform bend radius in operation

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoiduniform bend radius

Core Design Contradiction:

Ease of manufactureVSStability of the object's composition

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS9795765B2Variable stiffness steering mechanism for catheters

Publication Date: 2017.10.24 ST JUDE MEDICAL INT HLDG SARL

AI summary

A catheter assembly including a tapered steering spine having a varying stiffness along an axial length. The tapered steering spine is tailored to provide increasing flexibility from proximal to distal in a way that makes the bend radius more uniform along the length of the steering section. In one embodiment, the tapered steering spine includes structures on adjacent rings that engage with each other when the steering section is flexed to limit the minimum bend radius to a predetermined minimum and which enhances the torsional rigidity of the steering section regardless of the degree of flexure of the steering section. The limited bend radius can prevent excessive bending of components such as fiber optics. The enhanced torsional rigidity can negate the need for torque braid in the section of the catheter shaft that surrounds the tapered steering spine.