Fiber-Reinforced Spinal Brace Rod for MRI-Safe Rigidity
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Solution Overview
Problem
Metal fixture rods for spinal fixation cause image disturbance in MRI due to magnetization and lack sufficient rigidity and durability due to low fiber density.
Innovation Solution
A fixture rod comprising a core member and reinforcing fiber layer with long fibers and oblique fiber layers, using materials like carbon, glass, or SiC fibers combined with resins such as PEEK, to enhance rigidity and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal is used as fixture rod material, then fixing force and strength are improved, but magnetic field interference occurs during MRI imaging
Solution Approach 1:
The patent employs a composite rod structure combining metal core member with fiber-reinforced resin layers (carbon, glass, or aramid fibers). This composite construction provides the strength and fixing force of metal while the non-magnetic fiber layers block magnetic field interference, eliminating MRI image distortion without sacrificing mechanical performance.
2Adaptability or versatility
If fiber density is reduced in polymer rod, then flexibility is improved, but rigidity and durability are worsened
Solution Approach 1:
The patent applies different fiber densities and orientations to different regions and layers of the rod. The outer fiber-reinforced resin layer has high fiber density (60-80% volume fraction) for rigidity, while the inner core provides flexibility. Oblique fiber layers at ±45° angles provide torsional flexibility, whereas axial fibers provide bending rigidity, achieving local optimization of both properties.
Solution Approach 2:
The patent combines metal core member with fiber-reinforced resin composite layers to create a hybrid structure that achieves both flexibility and rigidity. The composite material system allows tuning of mechanical properties through fiber selection, orientation, and density distribution.
3Strength
If fiber content is increased in reinforcing fiber layer, then rigidity is improved, but manufacturing complexity increases
Solution Approach 1:
The patent divides the rod into segmented layers: metal core member, multiple fiber-reinforced resin layers with different fiber orientations (axial and oblique), and outer resin layer. Each layer can be manufactured separately using automated fiber placement or winding processes, then bonded together, simplifying the manufacturing of high-fiber-content structures while achieving superior rigidity.
Data Source
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AI summary
A fixture rod which reduces damage at the time of fixing with a screw, has high rigidity, and has high durability against a deformation load is provided. A fixture rod according to one embodiment of the present invention is configured to comprise a core member and a reinforcing fiber layer provided on the core member.