Non-buckling Steerable Catheter via Segmented Stiffness
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Solution Overview
Problem
Steerable catheters face issues with buckling when force is exerted on pull wires, leading to reduced precision and potential injury to sensitive anatomy, especially in confined spaces.
Innovation Solution
A steerable member with a continuous elongated body having a proximal section less flexible than the distal section, featuring a pull wire sheath that extends through the proximal and middle sections but not the distal section, and a pull wire affixed to the distal end, allowing the distal section to bend without buckling by varying the durometer and incorporating a stainless steel ribbon braid and coil tube for enhanced stiffness and force transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If pull wires are used to steer the catheter distal tip, then steering capability is achieved, but the proximal section buckles under compression force
Solution Approach 1:
The catheter body is divided into multiple sections with different flexibility characteristics. The proximal section has higher stiffness to resist buckling, while the distal section has lower stiffness to enable bending. This segmentation allows the catheter to maintain structural stability in the proximal region while achieving steerable functionality in the distal region.
Solution Approach 2:
Different sections of the catheter body are assigned different mechanical properties. The proximal section uses a polymer with higher durometer and includes reinforcement structures (ribbon braid, coil tube) to provide stiffness and prevent buckling. The distal section uses a polymer with lower durometer to allow easy bending for steering. This local differentiation of material properties resolves the contradiction between needing stability and needing flexibility.
2Measurement precision
If the catheter is made more flexible to enable bending, then steering precision is improved, but buckling resistance is reduced
Solution Approach 1:
The catheter is segmented into proximal and distal sections with different flexibility levels. The proximal section maintains high stiffness for buckling resistance, while the distal section has low stiffness for precise bending control. This segmentation enables the catheter to achieve steering precision without compromising overall buckling resistance.
Solution Approach 2:
The catheter employs local quality differentiation where the distal section uses softer polymer material for precise steering, while the proximal section uses stiffer material for structural support. This localized material property variation allows the catheter to exhibit both high steering precision and high buckling resistance in different regions.
3Stability of the object's composition
If steel coil tubes are embedded to reduce buckling, then buckling is mitigated, but the wires are still subjected to tension and distal tip curvature occurs
Solution Approach 1:
The reinforcement structures (ribbon braid and coil tube) are strategically positioned in the proximal section where buckling resistance is needed, while the distal section remains flexible for steering. This localized reinforcement approach allows the catheter to resist buckling in the proximal region while maintaining the ability to bend the distal tip through wire tension without excessive curvature.
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 prevents buckling of the catheter body, enabling precise steering and navigation through small spaces without exerting lateral forces on anatomy, thus improving the catheter's functionality and safety.
Implementation Method 1
the proximal section of the elongated body is less flexible than the distal section
Implementation Method 2
the distal section of the elongated body bends in response to a force applied to the proximal end of the pull wire
Data Source
AI summary
A steerable member is disclosed generally having a steerable member for a medical apparatus, including a continuous, elongated body having a proximal section, a distal section, and a middle section between the proximal and distal sections, where the proximal section of the elongated body is less flexible than the distal section. At least one pull wire sheath extends through the proximal section and the middle section, but not through the distal section, and has a channel therethrough. A pull wire is disposed in the channel of the sheath and extends through the proximal section, middle section and distal section of the elongated body, the pull wire having a distal end affixed to a distal end of the elongated body, so that the distal section of the elongated body bends in response to a force applied to the proximal end of the pull wire.