Lipid Layer for Orthopedic Taper Junction Fretting Corrosion

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Solution Overview

Problem

Modular orthopedic implants with conical taper junctions experience fretting corrosion due to micromotion, leading to adverse local tissue reactions, pain, and potential revision needs, as the flexible nature of the neck region allows for motion that generates metallic and metal-oxide corrosion-wear debris.

Innovation Solution

Incorporating lipids or a lipid-like substrate within the taper junction of modular orthopedic implants to increase the onset load and reduce corrosion, with the lipid layer applied over the male portion of the trunnion, enhancing seating displacement and pull-off load, and potentially acting as a lubricant to increase taper stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If modular components are assembled with conical taper junctions to provide adaptability and ease of replacement, then adaptability and ease of repair are improved, but micromotion at the interface occurs leading to fretting corrosion and reduced reliability

Engineering Contradiction:

ImproveadaptabilityVSAvoidreliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

A lubricant layer is introduced as an intermediary substance between the male and female taper components. This lubricant layer reduces direct metal-to-metal contact, thereby minimizing micromotion and preventing fretting corrosion while allowing the modular components to maintain their adaptive assembly capabilities

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The friction characteristics at the taper interface are modified by changing the surface conditions through lubricant application. This parameter change reduces the coefficient of friction, allowing the components to achieve a more stable interface with less micromotion under load

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If the neck region is made flexible to allow intraoperative adjustment, then ease of operation is improved, but micromotion increases causing fretting corrosion and adverse tissue reactions

Engineering Contradiction:

Improveease of operationVSAvoidfretting corrosion

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The lubricant acts as a protective intermediary between the flexible neck region and the head component, reducing direct contact and friction during intraoperative adjustment. This prevents the generation of corrosive wear debris while maintaining the flexibility needed for surgical adjustment

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The lubricant layer is applied beforehand to the taper interface, creating a protective cushion that prevents direct metal-to-metal contact. This pre-established protective layer cushions against micromotion and prevents fretting corrosion before it can occur during surgical operation

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 use of lipids significantly reduces fretting corrosion by increasing the load required to initiate corrosion, often eliminating it, and enhances taper locking stability, as evidenced by increased seating displacement and pull-off loads, while maintaining low micromotion and subsidence during testing.

Implementation Method 1

The flexible nature of the neck region allows for intraoperative adjustability but also enables micromotion during loading, which can lead to fretting corrosion. The incorporation of lipids or a lipid-like substrate within the taper junction increases the onset load and decreases the amount of corrosion.

Methodology Applied

Scientific EffectLubrication: Lubrication

Implementation Method 2

Micromotion on metallic surfaces can cause fretting and increased corrosion as a result (fretting corrosion). These modes of damage can generate metallic and metal-oxide corrosion-wear debris and these products have been associated with adverse local tissue reactions.

Methodology Applied

Scientific EffectFretting corrosion: Tribocorrosion

Data Source

PatentUS10806822B2Use of lipids for preventing fretting corrosion in the modular tapers of orthopedic implants

Publication Date: 2020.10.20 SYRACUSE UNIVERSITY

AI summary

The use of lipids in the taper junction or other metal on metal interface of a modular orthopedic implant to prevent fretting corrosion and increase the pull off load. The incorporation of lipids or a lipid-like substrate within the taper junction increases the onset load and decreases the amount of corrosion. The incorporation of lipids also increases the pull-off load necessary to separate the head from the neck. As a result, the use of lipids in the taper junction of an orthopedic implant should reduce the need for revisions of implants, such as such as knee and hip replacements, which are often needed because of fretting corrosion.