Removable Vena Cava Filter with Twisted Struts

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Solution Overview

Problem

Conventional vena cava filters become permanently implanted due to endotheliosis and are difficult to remove, and they often become off-centered or tilted during deployment, leading to increased endothelialization and reduced effectiveness.

Innovation Solution

A removable vena cava filter design featuring primary and secondary struts with varying thickness and tensile strength, along with twisted secondary struts to enhance centering and prevent entanglement, and a retrieval hook for simplified delivery and removal, made from superelastic materials like stainless steel or Nitinol.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a vena cava filter is deployed to capture thrombi, then thrombus capture effectiveness is improved, but endothelialization occurs along the filter struts leading to permanent implantation

Engineering Contradiction:

Improvethrombus capture effectivenessVSAvoidendothelialization

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The filter is divided into primary struts and secondary struts with different functions. Primary struts provide structural support and thrombus capture, while secondary struts provide centering forces. This segmentation allows the centering function to be separated from the thrombus capture function, reducing endothelialization at the hub while maintaining effectiveness.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different parts of the filter have different properties: primary struts are thicker and stronger for structural integrity, while secondary struts are thinner and more flexible for centering. The hub is designed with specific geometry to minimize endothelialization. This local differentiation optimizes each component's function while reducing overall harmful effects.

Inventive Principle:

Principle #3Local quality

2Reliability

If a conventional filter is deployed, then thrombus filtering is achieved, but the filter becomes off-centered or tilted leading to increased endothelialization

Engineering Contradiction:

Improvefiltering functionVSAvoidfilter centering

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The secondary struts act as counterbalancing elements that provide centering forces opposite to the off-centering forces generated by the hub and primary struts. This counterbalancing mechanism actively corrects tilting and maintains the filter in a centered position, preventing increased endothelialization.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

Solution Approach 2:

The filter design changes geometric parameters of the struts - primary struts have greater thickness and tensile strength while secondary struts have smaller dimensions. This parameter differentiation creates appropriate stiffness characteristics where primary struts are rigid for support and secondary struts are more compliant for centering adjustments.

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If a removable filter is designed, then retrieval becomes possible, but the filter must resist endothelialization forces during implantation

Engineering Contradiction:

Improvefilter retrievalVSAvoidresistance to endothelialization forces

Core Design Contradiction:

Ease of operationVSStrength

Solution Approach 1:

The filter incorporates dynamic elements - secondary struts that can flex and adjust their position to provide centering forces. This dynamic capability allows the filter to adapt to vessel geometry while maintaining centered position, reducing endothelialization forces that would otherwise prevent retrieval.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The filter uses composite construction with primary struts made of stronger material for structural integrity and secondary struts made of more flexible material for centering. This composite approach allows the filter to maintain strength where needed while having compliance where flexibility reduces endothelialization.

Inventive Principle:

Principle #40Composite materials

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 filter effectively captures thrombi while minimizing endothelialization and facilitating easy retrieval, maintaining effectiveness and preventing permanent implantation.

Implementation Method 1

made from superelastic materials like stainless steel or Nitinol

Methodology Applied

Scientific EffectSuperelasticity: Pseudoelasticity

Data Source

PatentUS7625390B2Removable vena cava filter

Publication Date: 2009.12.01 COOK MEDICAL TECHNOLOGIES LLC

AI summary

The present invention provides a removable vena cava filter for capturing thrombi in a blood vessel. The filter comprises a plurality of primary struts having first ends attached together along a longitudinal axis. Each primary strut includes an arcuate segment having a first tensile strength. The arcuate segment extends from the first end to an anchoring hook. The anchoring hook is integral with the arcuate segment and having the first thickness and first tensile strength. The filter further comprises a plurality of secondary struts freely spaced between the primary struts and having connected ends attached together along the longitudinal axis. Each secondary strut freely extends from the connected end to a free end avoiding contact with other secondary struts and primary struts. Each secondary strut has a second tensile strength.