Multi-Layer Suspension Liner for Irregular Residual Limbs
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Solution Overview
Problem
Prosthetic suspension liners and sleeves face challenges in conforming to irregular residual limbs, accommodating a variety of limb sizes, and providing enhanced comfort and pressure distribution while maintaining strength and durability.
Innovation Solution
A multi-layered suspension liner with a stiffer first elastomeric layer and a softer second layer, combined with a fabric layer, offering variable thickness and radial thickness variations to improve conformance and cushioning, particularly for bony areas, and featuring peripheral profiles for easier knee flexion and increased stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single-layer elastomeric liner is used, then the liner provides basic cushioning and comfort, but it cannot adequately accommodate irregular residual limb surfaces and varying limb sizes
Solution Approach 1:
The liner is divided into multiple layers with distinct functions: a first elastomeric layer for conforming to the residual limb surface, a second elastomeric layer for additional cushioning, and a fabric layer for structural support and breathability. Each layer addresses specific conformance requirements while collectively providing versatile adaptation to various limb geometries
Solution Approach 2:
The liner incorporates regions of varying thickness and material properties within different layers. The first elastomeric layer has variable thickness to accommodate bony prominences and soft tissue areas, while the second layer provides localized cushioning where needed. This local variation in material properties enables the liner to conform to irregular surfaces without requiring a completely custom design for each limb
2Object-affected harmful factors
If the liner material is made softer to improve comfort and cushioning, then comfort increases, but the liner loses strength and durability
Solution Approach 1:
The liner combines multiple elastomeric materials with different durometers and a fabric layer to create a composite structure. The softer elastomeric layers provide comfort and cushioning against the residual limb, while the fabric layer and tighter-knit regions provide structural strength and durability. This composite approach allows the liner to simultaneously achieve softness for comfort and strength for longevity
Solution Approach 2:
Different regions of the liner have different material compositions and thicknesses. Areas requiring higher cushioning have thicker softer elastomeric layers, while areas requiring higher strength have thinner layers or reinforced fabric construction. This localized variation in material properties allows the liner to provide comfort where needed while maintaining overall structural integrity
3Ease of manufacture
If the liner is made with uniform thickness to simplify manufacturing, then manufacturing is easier, but it cannot provide optimal pressure distribution across different anatomical regions
Solution Approach 1:
The first elastomeric layer is formed with variable thickness, having greater thickness at regions corresponding to bony prominences and softer tissue areas, and reduced thickness at regions with more robust soft tissue coverage. This non-uniform thickness profile enables optimal pressure distribution across different anatomical regions while still using a single continuous layer that can be manufactured using conventional molding techniques
Solution Approach 2:
The liner design varies the thickness parameter of the elastomeric layers across different radial positions to optimize pressure distribution. By changing the thickness parameter locally rather than uniformly, the liner achieves better pressure management without requiring complex multi-piece construction or post-manufacturing assembly
4Object-affected harmful factors
If the liner provides extensive cushioning to improve comfort, then comfort increases, but the liner loses stability and proprioception
Solution Approach 1:
The liner provides extensive cushioning through the elastomeric layers at regions where soft tissue coverage is limited, such as over bony prominences. However, the fabric layer and tighter-knit regions provide structural stability and proprioceptive feedback. This localized differentiation allows the liner to be comfortable without sacrificing stability
Solution Approach 2:
The combination of elastomeric materials and fabric creates a composite structure where the elastomeric layers provide compressible cushioning for comfort, while the fabric layer provides tensile strength and structural stability. This composite construction enables the liner to simultaneously deliver comfort through cushioning and stability through the reinforcing fabric network
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 liner provides improved comfort, stability, and proprioception by distributing pressure effectively, accommodating a range of limb sizes, and enhancing the amputee's control and comfort at the residual limb interface with a prosthesis.
Implementation Method 1
The liner includes a first layer defined by a first elastomeric material... a second layer defined by a second elastomeric material... The first layer is preferably stiffer than the second layer
Data Source
AI summary
A suspension liner for a residual limb has a liner body with a plurality of anterior and posterior projections formed from a thickness of the liner body. Medial and lateral tendons are located between and correspond to profiles of the plurality of the anterior and posterior projections such that the medial and lateral tendons are located on opposed sides of the liner body relative to one another. The medial and lateral tendons flare circumferentially toward proximal and distal sections of the liner body.