Asymmetric Curvature Vertebral Prosthesis Design
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Solution Overview
Problem
Existing artificial invertebral disk prostheses fail to accurately replicate the functions of natural invertebral disks, leading to issues such as loosening, dislodgement, premature wear, structural failure, and loss of normal spinal alignment due to unnatural stress distribution and subsidence.
Innovation Solution
A prosthesis design with an upper and lower part, where the center of radius of curvature is offset rearwardly, and the centroid of the contact surface is positioned on the same vertical axis as the center of rotation, allowing for balanced pressure distribution and reduced subsidence by creating a recessed area on the anterior portion of the end plate to prevent tilting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the prosthesis uses a central pivot design with symmetric curvature, then it simplifies the mechanical structure and ease of manufacture, but it causes unnatural stress distribution leading to subsidence and tilting of the end plates
Solution Approach 1:
The patent applies asymmetry by offsetting the center of curvature of the spherical surfaces from the central vertical axis of the prosthesis. The upper and lower parts have their centers of curvature positioned at different locations, creating an asymmetric stress distribution that replicates natural spinal mechanics and prevents subsidence and tilting of the end plates.
2Reliability
If the prosthesis uses a resilient deformable core to reproduce IAR variation, then it improves the replication of physiological motion, but it leads to premature materials wear and stress failure
Solution Approach 1:
The patent employs spherical surfaces with specific radii of curvature for the upper and lower parts. This curvature design allows for controlled rotation and movement while distributing stresses evenly across the spherical interfaces, avoiding the material wear and stress concentration problems associated with resilient deformable cores.
3Stability of the object's composition
If the center of curvature is positioned on the central vertical axis, then it maintains symmetric load distribution, but it causes posterior subsidence and tilting of the upper end plate
Solution Approach 1:
The patent deliberately positions the centers of curvature asymmetrically relative to the central vertical axis. This asymmetric positioning creates a controlled offset that prevents posterior subsidence and tilting of the upper end plate while maintaining stable load distribution across the prosthesis interfaces.
Data Source
AI summary
A method for reducing prosthetic loading failure including the steps of providing a prosthesis for a vertebral column comprising at least an upper part for attachment to an upper vertebrae and a lower part for attachment to a lower vertebrae, the upper part having a lower curved surface and the lower part having an upper curved surface, wherein the upper and lower curved surfaces have a center of radius of curvature offset rearwardly with respect to a central vertical axis through the upper and lower vertebrae, and positioning the centroid of at least one of the upper and lower parts substantially on the same vertical axis of the center of radius of curvature.