Amputation Stump Casting Liner for Uniform Radial Pressure

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Solution Overview

Problem

Existing methods for molding amputation stumps in prosthetics fail to provide uniform pressure, are not portable, and do not allow manual or optical reshaping, especially when used by less experienced technicians.

Innovation Solution

A method using a liner with an expansion coupling that lengthens longitudinally to reduce circumference, applying radial force for uniform pressure, and an impression aid with a height-adjustable holding device for easy handling and transport, allowing optical scanning or reshaping.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stress or pressure

If conventional plaster casting methods are used, then the method is simple and low cost, but uniform pressure cannot be exerted on the stump and manual influence is lost

Engineering Contradiction:

Improveuniform pressure distributionVSAvoidmolding device complexity

Core Design Contradiction:

Stress or pressureVSDevice complexity

Solution Approach 1:

The patent uses a flexible liner made of elastomeric material that conforms to the stump surface. This flexible shell transmits pressure uniformly across the stump surface while remaining simple in structure, resolving the contradiction between achieving uniform pressure and maintaining device simplicity.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The patent employs an inflatable bladder system that uses pneumatic pressure to exert uniform force on the stump. By inflating the bladder, uniform pressure is distributed across the entire stump surface, while the system remains relatively simple and portable compared to rigid hydraulic systems.

Inventive Principle:

Principle #29Pneumatics and hydraulics

2Ease of operation

If portable molding methods are used, then ease of transport is improved, but the ability to exert uniform pressure and allow manual influence is reduced

Engineering Contradiction:

Improveportability and ease of handlingVSAvoiduniform pressure application

Core Design Contradiction:

Ease of operationVSStress or pressure

Solution Approach 1:

The molding system is divided into separate components: a portable liner, an inflatable bladder, and a holding device. This segmentation allows the system to be transported easily in parts while maintaining the capability to exert uniform pressure when assembled, resolving the contradiction between portability and pressure application capability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system uses a dynamic inflatable bladder that can be adjusted during the molding process. This allows the device to adapt to different stump sizes and shapes while maintaining uniform pressure, and the entire system remains portable and easy to set up in clinical environments.

Inventive Principle:

Principle #15Dynamics

3Strength

If the stump is covered with plaster and rubber sleeve, then the stump is protected, but suboptimal loading occurs and uniform pressure is not achieved

Engineering Contradiction:

Improvestump protectionVSAvoidloading uniformity

Core Design Contradiction:

StrengthVSStress or pressure

Solution Approach 1:

The patent replaces the rigid plaster and rubber sleeve combination with a flexible elastomeric liner that directly contacts the stump. This flexible shell provides protection while conforming to the stump surface, ensuring uniform pressure distribution and optimal loading throughout the molding process.

Inventive Principle:

Principle #30Flexible shells and thin films

4Measurement precision

If optical scanning is used, then measurement precision is improved, but the ability to manually influence the impression result is lost

Engineering Contradiction:

Improvesurface topography accuracyVSAvoidmanual influence capability

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The system allows manual shaping and adjustment of the plaster model while it is still pliable, before final hardening. This preliminary manual action enables the orthotist to influence the impression result, and subsequently optical scanning can be performed on the manually adjusted model, combining both advantages.

Inventive Principle:

Principle #10Preliminary action

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

Ensures uniform and full-surface loading of the amputation stump, enabling manual reshaping and optical scanning, while being portable and easy to use, thus improving the molding process.

Implementation Method 1

the liner has an expansion coupling such that an extension of the liner along the longitudinal direction inevitably results in a reduction of the circumference

Methodology Applied

Scientific EffectPoisson's effect: Poisson's Effect

Data Source

PatentEP3419566B1Method and device for casting a stump

Publication Date: 2025.09.10 OTTOBOCK SE & CO KGAA

Figure 1A~1B
Figure 2A~2B
Figure 3

AI summary

The invention relates to a method for making a mould of an amputation stump, in which the amputation stump is inserted into a liner of a moulding aid, said liner having a longitudinal direction and a circumference, and said liner having an expansion coupling such that when the liner is extended in the longitudinal direction, this necessarily results in a reduction of the circumference.