Fluid Pressure Vessel Membrane for Accurate Prosthetic Stump Casting
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Solution Overview
Problem
Conventional methods for creating plaster casts for leg prostheses often result in inaccuracies due to the inability to account for soft tissue displacements under load, leading to discomfort and inefficiencies in manufacturing.
Innovation Solution
A medical device featuring a fluid container with a pressure chamber and a membrane that allows for even pressure distribution around the limb stump, enabling the creation of a plaster cast while the patient is standing, thus simulating the loading conditions of the prosthesis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional plaster casting methods are used with the patient sitting or lying down, then the manufacturing process is simple, but the plaster cast does not accurately reflect soft tissue displacements under load, resulting in poor fit accuracy
Solution Approach 1:
The patent employs a pressure vessel filled with fluid (water or air) to apply uniform hydrostatic pressure to the membrane, which in turn applies even pressure to the plaster cast and limb stump. This pneumatic/hydraulic system enables the patient to stand during casting, accurately capturing soft tissue displacements under load while maintaining a relatively simple device structure.
Solution Approach 2:
A membrane made of flexible material (such as rubber or plastic) is used to separate the pressure chamber from the casting chamber. The membrane transmits pressure uniformly to the plaster cast while conforming to the shape of the limb stump, enabling accurate capture of soft tissue contours and displacements without requiring complex rigid structures.
2Manufacturing precision
If the patient stands during plaster casting to simulate loading conditions, then the fit accuracy improves, but it becomes difficult to prevent axial reaction forces from displacing the limb stump
Solution Approach 1:
The patent uses the buoyant force of the fluid in the pressure chamber to counteract the axial reaction forces generated when the patient stands. The fluid provides an upward buoyant force that balances the downward gravitational force on the limb stump, preventing displacement while allowing the patient to bear weight and accurately capture soft tissue displacements under load.
3Ease of operation
If even pressure distribution is applied around the limb stump during plaster casting, then the fit comfort improves, but the device structure becomes more complex
Solution Approach 1:
The membrane acts as a flexible intermediary that distributes pressure uniformly across the surface of the plaster cast and limb stump. When fluid pressure is applied to one side of the membrane, it flexes and transmits the pressure evenly to the other side, conforming to the contours of the limb stump and ensuring comfortable fit without requiring complex mechanical pressure distribution mechanisms.
Solution Approach 2:
The use of incompressible fluid (water) or compressible fluid (air) in the pressure chamber provides uniform hydrostatic pressure distribution throughout the chamber. This fluid pressure system automatically ensures even pressure application to all surfaces in contact with the membrane, simplifying the pressure distribution mechanism while improving fit comfort.
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
This method allows for a more accurate and comfortable fit of the prosthesis socket by replicating the loading conditions during the plastering process, reducing manual intervention and improving the fit of the prosthetic limb.
Implementation Method 1
The fluid container can optionally have a pressure chamber. The pressure vessel has one or more pressure chambers or one or more fluid chambers that can accommodate or store an optionally pressurized fluid
Data Source
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AI summary
The invention relates to a medical device (100) for use in manufacturing a plaster impression of a limb stump, in particular a lower leg stump, wherein the device (100) has a pressure vessel (1) having a fluid chamber or pressure chamber (DK) for receiving or storing a pressurized fluid (F). The pressure vessel (1) has a wall (3) made of a first material, wherein the wall (3) delimits an interior (I) of the pressure vessel (1) with respect to an exterior (Ä), wherein the pressure vessel (1) has an inlet opening (9) for introducing the limb stump (KS) into the interior (I) of the pressure vessel (1), and has a fluid-tight membrane (5) made of a second material, which is arranged to form or delimit the fluid chamber or pressure chamber (DK). An upper section of the membrane (5) is, preferably detachably, fastened to the pressure vessel (1) by means of a connector (53).