Concentric Fitting Pull-Wire Assembly for Compact Catheter Steering

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Solution Overview

Problem

Steerable medical devices face issues with pull wire breakage and whipping due to low tensile strength and torque response, particularly in minimally invasive procedures with smaller catheters.

Innovation Solution

A medical device configuration with a handle, shaft, and fittings that allow for controlled movement of pull wires, including a movable body and articulable portions, to enhance steering and reduce breakage risk.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If smaller catheters are used for minimally invasive procedures, then patient trauma is reduced, but pull wire tensile strength and torque response deteriorate

Engineering Contradiction:

Improvecatheter sizeVSAvoidpull wire tensile strength

Core Design Contradiction:

Weight of moving objectVSStrength

Solution Approach 1:

The catheter is divided into multiple segments including a pull wire, articulation section, and shaft. The pull wire is segmented into multiple wires (e.g., four wires) that can be independently controlled, distributing the mechanical load and improving overall tensile strength while maintaining a small catheter profile.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The pull wire assembly uses composite construction combining multiple materials with different properties. The pull wires are made from materials with high tensile strength, the articulation section uses materials with appropriate flexibility, and the shaft provides structural support. This composite approach allows small catheter dimensions while maintaining sufficient mechanical strength.

Inventive Principle:

Principle #40Composite materials

2Weight of moving object

If smaller catheters are used for minimally invasive procedures, then patient trauma is reduced, but torque response deteriorates

Engineering Contradiction:

Improvecatheter sizeVSAvoidtorque response

Core Design Contradiction:

Weight of moving objectVSForce

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The articulation section incorporates dynamic joints that allow controlled movement and rotation. These joints provide mechanical advantage, amplifying the torque generated by the pull wires. The dynamic structure enables effective torque transmission despite the small catheter size, maintaining steering responsiveness.

Inventive Principle:

Principle #15Dynamics

3Device complexity

If traditional pull wire steering is used, then device simplicity is maintained, but whip-like movement and breakage risk increase

Engineering Contradiction:

Improvesteering mechanism simplicityVSAvoidpull wire breakage resistance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The articulation section acts as a cushioning element between the pull wire and the catheter tip. It absorbs and dissipates the whip-like movements and torque fluctuations before they can propagate to the pull wire, reducing stress concentrations and preventing breakage before they occur.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

4Ease of operation

If articulation section with multiple fittings is added, then steering control is improved, but device complexity increases

Engineering Contradiction:

Improvesteering controlVSAvoidnumber of fittings

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

Multiple fittings are merged into an integrated articulation section assembly. The fittings are combined with the articulation joints and pull wire attachments to form a unified structure, reducing the number of separate components and simplifying assembly while maintaining precise steering control.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The fittings are designed with multi-functionality, serving multiple purposes simultaneously. For example, fittings provide both structural support and articulation movement, or serve as both attachment points for pull wires and guides for wire routing. This reduces the total number of fittings needed while improving steering control.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS20250235666A1Medical systems, devices, and related methods for steering or deflecting a portion of a medical device

Publication Date: 2025.07.24 BOSTON SCIENTIFIC SCIMED INC

AI summary

Medical devices and related methods are described. The medical device includes a handle including a movable body, a shaft extending from a distal end of the handle, a first fitting coupled to the shaft, and a second fitting distal to the first fitting and concentrically coupled to the shaft. The second fitting includes a first hole and a second hole. The first hole receives a portion of the shaft, and the second hole is aligned with the first fitting. A third fitting surrounds the shaft, the first fitting, and the second fitting. The third fitting includes a distal face, a third hole, and a fourth hole. The third hole receives a distal portion of the shaft, and the fourth hole is aligned with the second hole and a wire. A proximal portion of the wire is coupled to the first fitting.