Composite Spinal Brace Rod Structure for MRI-Safe Fixation
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Solution Overview
Problem
Conventional metal fixture rods for spinal fixation face issues such as magnetic interference during MRI imaging and low rigidity, leading to difficulty in diagnosis and inadequate strength and durability.
Innovation Solution
A fixture rod comprising a core member made of resin with embedded fibers, such as carbon, glass, or aramid, and a reinforcing fiber layer with aligned long fibers and oblique layers, providing a solid double structure for enhanced rigidity and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal is used for fixture rod, then fixing force and strength are improved, but magnetic field interference occurs during MRI imaging
Solution Approach 1:
The patent employs a composite structure consisting of a polymer core member reinforced with fiber layers (carbon, glass, aramid, or boron). This composite material provides metal-level strength and rigidity while being non-magnetic, thereby eliminating MRI interference. The fiber-reinforced polymer structure achieves the necessary mechanical properties without the harmful magnetic effects of metallic materials.
Solution Approach 2:
The invention changes the material parameters from metallic to polymer-based composites. By selecting specific fiber types and resin combinations, the rod achieves optimal strength-to-weight ratio and magnetic properties. The fiber orientation angles (0°, ±45°, 90°) are optimized to provide uniform mechanical performance in multiple directions while maintaining non-magnetic characteristics.
2Ease of manufacture
If fiber density is reduced in polymer rod, then manufacturing ease is improved, but rigidity and strength deteriorate
Solution Approach 1:
The patent uses a composite structure with a polymer core and multiple fiber reinforcement layers. The fiber content in the reinforcing fiber layer is optimized at 60 weight % or more to ensure high rigidity and strength. The combination of polymer matrix and high-density fiber reinforcement achieves both manufacturability and mechanical performance requirements.
Solution Approach 2:
The invention introduces multi-layer fiber arrangements with different orientations (0°, ±45°, 90°) to enhance mechanical properties in multiple dimensions. This layered approach distributes stress effectively and provides uniform strength characteristics without requiring excessive fiber density in a single layer, facilitating manufacturing while maintaining rigidity.
3Strength
If fiber content is increased in reinforcing fiber layer, then rigidity is improved, but manufacturing complexity increases
Solution Approach 1:
The rod is segmented into distinct functional layers: a polymer core member and multiple fiber-reinforced layers with specific orientations. Each layer has a defined fiber content (60 wt% or more in the reinforcing layer) and orientation angle, allowing standardized manufacturing processes for each segment while achieving complex overall performance requirements.
Solution Approach 2:
The patent optimizes fiber content at 60 weight % or more in the reinforcing fiber layer, which provides the necessary rigidity without excessive complexity. Specific fiber orientation angles (0°, ±45°, 90°) are standardized to simplify the manufacturing process while maintaining mechanical performance. This parameter optimization balances rigidity requirements with manufacturing feasibility.
4Object-affected harmful factors
If conventional polymer rod is used, then magnetic field interference is avoided, but durability against deformation load deteriorates
Solution Approach 1:
The patent creates a fiber-reinforced polymer composite that maintains the non-magnetic advantage of polymers while dramatically improving durability. The high fiber content (60 wt% or more) and optimized fiber orientations provide exceptional resistance to deformation loads and fatigue, achieving metal-like durability without magnetic interference.
Solution Approach 2:
The multi-layer fiber arrangement with varying orientations (0°, ±45°, 90°) provides comprehensive load-bearing capability in all directions. This dimensional reinforcement strategy ensures high durability against complex deformation loads while maintaining the non-magnetic polymer base material properties.
Data Source
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 disclosure is configured to comprise a core member and a reinforcing fiber layer provided on the core member.