Spiral Cut Transitional Geometry for Expandable Medical Devices

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Solution Overview

Problem

Medical instruments with rigid expandable devices, such as those made from nitinol or stainless steel, face challenges in coupling with flexible catheters or sheaths made of materials like nylon or PTFE, leading to potential cracking or breaking under mechanical strain during use in intraluminal passages.

Innovation Solution

A medical instrument design featuring a transitional portion with a spiral cut on its outer surface, which is either embedded within the catheter's wall or coupled with a sleeve, enhances flexibility and secure bonding by allowing the use of rigid materials while distributing strain effectively.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a rigid expandable device is coupled to a flexible catheter, then the expandable device can maintain structural integrity, but the coupling point is prone to cracking or breaking under mechanical strain

Engineering Contradiction:

Improvestructural integrity of expandable deviceVSAvoidcoupling reliability under strain

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The transitional portion is made with a different modulus of elasticity than the rest of the expandable device, creating a localized region with intermediate mechanical properties. This gradient structure allows the transition from rigid to flexible material properties, reducing stress concentration at the coupling point while maintaining overall structural integrity.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The expandable device incorporates a composite structure with a transitional portion made of material having intermediate modulus of elasticity between the rigid expandable device and flexible catheter. This composite approach combines materials with different mechanical properties to create a gradient transition zone that accommodates both rigidity and flexibility requirements.

Inventive Principle:

Principle #40Composite materials

2Strength

If a rigid expandable device is used, then it can provide necessary structural support, but it is difficult to couple with flexible catheters made of plastics

Engineering Contradiction:

Improvestructural support capabilityVSAvoidcoupling difficulty between rigid device and flexible catheter

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The modulus of elasticity parameter is changed in the transitional portion to create an intermediate value between the rigid expandable device and flexible catheter. This parameter gradient facilitates easier coupling by reducing the mechanical property mismatch between the two components.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10463351B2Transitional geometry for an expandable medical device

Publication Date: 2019.11.05 COOK MEDICAL TECHNOLOGIES LLC

AI summary

A medical instrument is provided including a device having an expandable portion and a transitional portion. The transitional portion has a spiral cut on the outer surface, and is aligned with the distal portion of a catheter. The transitional portion may be secured to the catheter by a sleeve which is coupled to both the catheter and the transitional portion. Alternatively, the portion of the transitional portion having the spiral cut may be embedded within the catheter.