Osseointegrated Limb Prosthesis Flexible Joint Force Distribution
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Solution Overview
Problem
Osseointegrated prostheses face limitations in handling bending and rotational forces, leading to restricted activity levels and risk of damage due to the need for weak implant dimensions to prevent bone overload, which limits freedom of movement and recommends avoiding activities like running.
Innovation Solution
A limb prosthesis with a flexible joint coupling mechanism that transfers bending and rotational forces away from the implant to a socket, allowing for higher loading and activity levels by distributing these forces through the soft tissues, thereby reducing the risk of damage to the implant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the implant dimensions are made weak enough to prevent bone overload, then bone damage is avoided, but the freedom of movement and maximum activity level are limited
Solution Approach 1:
A coupling device with a flexible joint acts as an intermediary between the implant and the prosthetic member. This flexible joint includes a first coupling member connected to the implant and a second coupling member connected to the prosthetic member, with a flexible connection between them that allows relative movement. This intermediary structure absorbs and distributes bending and rotational forces, protecting the implant from overload while enabling greater freedom of movement and higher activity levels including running.
2Strength
If the implant is made stronger to handle higher loads, then activity level increases, but the risk of bone tissue damage increases
Solution Approach 1:
The coupling device changes the mechanical parameters of force transmission by introducing a flexible joint with controlled compliance. The flexible connection allows relative movement between the first and second coupling members, transforming rigid force transmission into a compliant system that limits peak forces on the implant. This parameter change enables the implant to operate within safe load ranges while still supporting high activity levels through energy absorption and force distribution.
3Ease of operation
If traditional socket connection is used to connect prosthesis to body, then ease of connection is achieved, but tissue damage and instability occur due to pumping effect
Solution Approach 1:
The osseointegrated implant serves as an intermediary that eliminates the need for traditional socket connection. The implant is directly integrated into the bone, providing a stable anchor point for the prosthesis. This intermediary structure bypasses the soft tissues entirely, preventing the pumping effect and associated tissue damage while maintaining connection ease through a single surgical integration procedure.
Data Source
AI summary
A limb prosthesis which via coupling means is adapted to be connected to an implant in the form of an osseointegrated shaft projecting from an amputated stump. The coupling means comprises a flexible joint and the prosthesis further comprises at least one force transmitting device secured to and extending from a prosthetic member connected to the coupling means up to a position on the amputated stump or body portion to which the stump connects. The force transmitting device is adapted to be secured to the stump or other body portion in such a way that it relieves the implant from at least part of the bending and/or rotational forces exerted to the prosthetic member.