Bone Cement Cartridge Mixing With Depressurization Control
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Solution Overview
Problem
Existing methods for producing polymethyl methacrylate bone cement are prone to air inclusions due to the introduction of air bubbles during mixing, which can negatively affect the mechanical properties of the hardened cement, and there is a risk of unwanted injection of minuscule volumes of monomer liquid during the extrusion process.
Innovation Solution
A method and device using a cartridge with a central piston and drive piston system that allows for the controlled mixing and depressurization of monomer liquid, ensuring complete wetting of cement powder before depressurization to prevent the injection of additional monomer liquid into the cement dough.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional mixing methods are used to produce bone cement, then the mixing process is simple, but air inclusions occur which negatively affect mechanical properties
Solution Approach 1:
The patent applies preliminary action by creating a vacuum environment before mixing the bone cement components. The vacuum is established in the mixing chamber prior to introducing the powder and liquid, which prevents air from being trapped during the mixing process. This preliminary vacuum treatment ensures that no air inclusions are formed during subsequent mixing operations.
Solution Approach 2:
The patent creates an inert environment by maintaining a vacuum atmosphere in the mixing chamber during the entire mixing process. This vacuum environment replaces normal atmospheric conditions with a controlled vacuum state, preventing air from entering the mixture and eliminating the formation of air bubbles that would compromise mechanical properties.
2Strength
If vacuum cementing systems are used to avoid air inclusions, then mechanical properties improve, but device complexity increases
Solution Approach 1:
The patent merges the vacuum generation function with the mixing chamber by integrating a vacuum pump directly into the mixing device structure. The vacuum pump, mixing chamber, and component delivery systems are combined into a single integrated unit, eliminating the need for separate vacuum equipment and reducing overall system complexity while maintaining effective vacuum mixing.
Solution Approach 2:
The mixing chamber serves multiple functions: it acts as both the mixing vessel and the vacuum chamber, and also functions as the extrusion chamber. This multi-functionality reduces the number of separate components needed, simplifying the overall device structure while achieving effective vacuum mixing and eliminating air inclusions.
3Productivity
If monomer liquid is injected under pressure during extrusion, then mixing efficiency improves, but unwanted injection of monomer liquid occurs
Solution Approach 1:
The patent employs feedback control by using pressure sensors to monitor the pressure within the mixing chamber during extrusion. When the pressure exceeds a predetermined threshold that would cause unwanted monomer liquid injection, the system automatically adjusts or stops the extrusion process. This feedback mechanism ensures efficient mixing while preventing harmful over-injection of monomer liquid.
Solution Approach 2:
The patent applies dynamics by making the extrusion process adjustable and controllable in real-time. The extrusion rate and pressure are dynamically adjusted based on the mixing stage and material state, allowing optimal mixing efficiency while preventing unwanted injection. The system transitions from static fixed-pressure extrusion to dynamic adaptive extrusion control.
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 method and device ensure the production of a homogeneous bone cement by preventing the introduction of air bubbles and unwanted monomer liquid, resulting in improved mechanical properties and consistency of the cement.
Implementation Method 1
moving the drive piston toward the cartridge head, opening the monomer liquid container or rupturing the monomer liquid container via the movement of the drive piston toward the cartridge head, and thereby releasing the monomer liquid in the second cavity
Implementation Method 2
expelling residual gases through the central piston, through the cement powder, and through the closure, into the surroundings of the device, by means of the movement of the drive piston
Implementation Method 3
injecting the monomer liquid through the central piston into the cement powder by further moving the drive piston toward the cartridge head
Implementation Method 4
a central piston, wherein the central piston is permeable to gases and the monomer liquid and impermeable to the powder particles of the cement powder, wherein the central piston is arranged movably in the cylindrical interior of the cartridge towards the cartridge head and is arranged between the drive piston and the cartridge head, wherein the central piston separates the cylindrical interior of the cartridge into a first cavity and a second cavity
Implementation Method 5
a closure, wherein the closure is permeable to gases and impermeable to powder particles of the cement powder
Implementation Method 6
depressurizing the second cavity after steps A) to F), wherein the second cavity is depressurized by partially removing the monomer liquid contained in the second cavity
Implementation Method 7
wetting the powder particles of the cement powder
Data Source
AI summary
One aspect is a method for producing a bone cement from monomer liquid and cement powder using a depressurization device. The method is performed using a device comprising a cartridge having a drive piston, and a central piston being permeable to gases and the monomer liquid and impermeable to the cement powder and being arranged between the drive piston and a cartridge head. The method comprising the steps of expelling residual gases into the surroundings of the device by means of the movement of the drive piston; displacing gases between the powder particles with the inflowing monomer liquid; and depressurizing a cavity of the cartridge, by partially removing the contained monomer liquid. The invention also relates to such a device for mixing a bone cement, with a depressurization device.