Hinged Spinal Fixation Cage for Direct Graft Compression
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Solution Overview
Problem
Current spinal fixation systems lack the ability to directly compress the bone graft between the endplates of the vertebrae being fused, providing suboptimal rigidity, especially in weakened bone, and limiting the ability to conform to the spinal shape, thereby hindering optimal bone fusion.
Innovation Solution
A spinal fixation system with an expandable disc replacement body featuring adjustable walls connected by a hinge and an adjustment mechanism, allowing continuous variation of the angle between the walls, and incorporating bone-screw receiving sections with diverging longitudinal axes and snap rings to secure bone screws, enabling direct compression of the graft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a plate and cage are used in traditional spinal fixation, then bone fusion is supported, but the device cannot directly compress the bone graft between endplates
Solution Approach 1:
The patent merges the plate and cage into a single integrated screw-cage device that combines the functions of both components. The cage portion directly contacts and compresses the bone graft between the endplates, while the plate portion provides fixation, eliminating the need for separate components and enabling direct compression force application.
Solution Approach 2:
The screw-cage device performs multiple functions simultaneously: it provides structural support, secures bone grafts through direct compression, and facilitates bone fusion. The device acts as both a cage for graft compression and a plate for fixation, achieving multi-functionality in a single component.
2Strength
If screws are added to provide rigidity, then stability is improved, but the screws occupy space needed for bone graft compression
Solution Approach 1:
The device is segmented into distinct functional zones: the cage portion with internal volume for bone graft placement and compression, and the plate portion with screw holes for rigid fixation. This segmentation allows screws to be positioned in the plate section without occupying space in the cage section, enabling both rigidity and adequate graft volume.
3Ease of manufacture
If a mono-block device is used, then manufacturing is simplified, but the device cannot conform to the shape of the disc space
Solution Approach 1:
The device incorporates a hinge mechanism that allows the plate and cage portions to articulate relative to each other, enabling the device to adapt to the natural curvature and shape of the disc space. This dynamic articulation maintains conformability while the overall mono-block construction preserves manufacturing simplicity.
4Ease of operation
If the device cannot adjust the angle between walls, then the structure is simpler, but lordosis correction is limited
Solution Approach 1:
The hinge connection between the plate and cage portions enables dynamic angle adjustment, allowing the device to be positioned at various angles to correct lordosis. The hinge provides controlled mobility that facilitates surgical adjustment while maintaining structural integrity, balancing operational ease with manageable complexity.
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 system facilitates direct compression of the bone graft, enhances rigidity, conforms to the spinal shape, and allows for customizable lordosis correction, thereby optimizing bone fusion and reducing the need for multiple devices.
Implementation Method 1
an expandable disc replacement body including a first wall, a second wall, a hinge connecting the first wall and the second wall
Implementation Method 2
an adjustment mechanism positioned between the first wall and the second wall, wherein an angle between the first wall and the second wall can be continuously varied between a lower value of the angle and an upper value of the angle by movement of the adjustment mechanism
Implementation Method 3
incorporating bone-screw receiving sections with diverging longitudinal axes and snap rings to secure bone screws
Implementation Method 4
enabling direct compression of the graft
Data Source
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AI summary
A spinal fixation system includes an expandable disc replacement body and an adjustment mechanism. The expandable disc replacement body includes a first wall, a second wall, a hinge connecting the first wall and the second wall, and a first bone-screw receiving section at a proximal end of the first wall. The adjustment mechanism is positioned between the first wall and the second wall, and an angle between the first wall and the second wall can be varied by movement of the adjustment mechanism.