Pivoting Arms for Ankle Prosthesis Fixation

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Solution Overview

Problem

Current ankle joint replacement prostheses face challenges in achieving stable attachment to bones, especially in cases with compromised soft tissue or bone quality, where existing solutions fail to provide adequate grip and stability.

Innovation Solution

An ankle prosthesis design featuring a talar component with pivoting or flexing arms that engage a previously formed slot in the talus bone, allowing for secure attachment to both cancellous bone and cortical walls, using a driving mechanism to expand and grip the bone surfaces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional screw or rod fixation is used, then the prosthesis can be attached to the bone, but adequate grip and stability are not achieved in cases with compromised soft tissue or bone quality

Engineering Contradiction:

Improvefixation stabilityVSAvoidadaptability to compromised bone quality

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The fixation mechanism employs dynamic arms that can pivot and flex outwardly during insertion to engage the bone slot, transitioning from a static fixation state to a dynamic engagement state. This allows the arms to adapt to varying bone conditions and achieve secure fixation in compromised bone quality scenarios.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The arms are designed with changeable geometric parameters through pivoting and flexing motions, allowing them to adjust their engagement depth and orientation. This parameter change capability enables the fixation mechanism to accommodate different bone densities and slot configurations, improving adaptability to compromised bone quality.

Inventive Principle:

Principle #35Parameter changes

2Strength

If the arms are made rigid for strong engagement, then grip strength is improved, but the ability to flex and pivot for proper engagement is reduced

Engineering Contradiction:

Improvegrip strengthVSAvoidflexibility during engagement

Core Design Contradiction:

StrengthVSEase of operation

Solution Approach 1:

The fixation mechanism is segmented into multiple functional components: rigid arm bodies for strength, pivotal joints for rotation, and flexible sections for bending. This segmentation allows each component to perform its specific function optimally - the rigid portions provide grip strength while the pivotal and flexible portions enable proper engagement during insertion.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The arms are constructed using composite material structures that combine rigid materials for the arm bodies with flexible elements for the bending sections. This composite construction allows the arms to exhibit both high strength for gripping and sufficient flexibility for pivoting and flexing during the engagement process.

Inventive Principle:

Principle #40Composite materials

Data Source

PatentUS11357637B2Fixation mechanism for an implant

Publication Date: 2022.06.14 WRIGHT MEDICAL TECHNOLOGY INC

AI summary

An ankle prosthesis has a tibial component configured for attachment to a tibia of a person, and a talar component. The talar component has a first surface configured for facing the tibial component and a second surface configured for facing a talus of the person. The second surface has first and second arms attached to it, for pivoting or flexing outwardly in medial and lateral directions, respectively, to engage side surfaces of a previously formed slot in the talus.