Composite Bone Screw with 3D Printed Metallic Outer Layer
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Solution Overview
Problem
Metallic bone screws interfere with medical imaging and radiotherapy, cause stress shielding, and have biocompatibility issues due to their rigid nature and potential for corrosion, while composite materials offer reduced stress shielding and imaging artifacts but may lack shear resistance.
Innovation Solution
A composite material bone screw with a thin, 3-D printed metallic outer layer that is electro-polished and compression molded onto a fiber-reinforced polymer matrix, providing shear resistance and reduced imaging artifacts through geometrical interlocking structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metallic outer layer is used to provide shear resistance, then the screw can resist shearing forces during rotation, but the metallic layer interferes with medical imaging and radiotherapy
Solution Approach 1:
The patent applies a metallic outer layer only to specific regions of the screw where shear resistance is most needed, rather than covering the entire screw. This localized application provides the necessary mechanical strength at critical interfaces while minimizing the volume of metal that interferes with medical imaging and radiotherapy.
Solution Approach 2:
The patent creates a composite structure combining metallic outer layer material with polymer or ceramic core material. This composite construction provides the shear resistance of metal while the non-metallic core reduces imaging artifacts and allows for better MRI compatibility and reduced radiotherapy interference.
2Object-affected harmful factors
If a thin metallic outer layer is used to reduce imaging artifacts, then less interference with medical imaging occurs, but the shear resistance may be insufficient
Solution Approach 1:
The patent employs a composite structure where a thin metallic outer layer is combined with a high-strength polymer or ceramic core. The thin metal layer provides sufficient shear resistance at the thread-bone interface while the non-metallic core maintains structural integrity and minimizes imaging artifacts.
Solution Approach 2:
The patent optimizes the thickness parameter of the metallic outer layer to a specific range that balances shear resistance requirements with imaging compatibility. By precisely controlling the metal layer thickness and selecting appropriate material properties, the design achieves adequate mechanical performance while minimizing radiopacity and MRI artifacts.
3Reliability
If compression molding is used to attach the metallic layer to the composite material, then strong bonding is achieved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent combines the metallic outer layer and composite core into a single integrated component through compression molding, eliminating the need for separate attachment steps. This merging of materials during manufacturing creates strong interfacial bonding while streamlining the production process.
Solution Approach 2:
The compression molding process utilizes phase transitions of the polymer or ceramic material during molding to achieve strong bonding between the metallic layer and composite core. The controlled application of heat and pressure during molding ensures proper material flow and interfacial adhesion.
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 solution enhances shear resistance and reduces imaging artifacts, maintaining the strength and biocompatibility benefits of composite materials while minimizing the drawbacks of metallic screws.
Implementation Method 1
the metallic outer layer being electro-polished
Implementation Method 2
the heating includes applying enough heat to melt a polymer portion of the composite material
Implementation Method 3
the compression molding includes causing composite material matrix to flow into prepared spaces of the metallic outer layer
Implementation Method 4
the metallic layer resists a shearing force applied to the metallic layer when the screw is rotated within the bone
Data Source
AI summary
A method of manufacturing fiber-reinforced polymer matrix composite material bone screws having threads surfaced with a metallic outer layer is described. In some embodiments, the method includes preparing a metallic outer layer by 3-D printing, inserting a composite material into the metallic outer layer, and attaching the metallic outer layer onto the composite material.