Intervertebral Disc Core Retention via Segmented Sliding
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Solution Overview
Problem
Current intervertebral disc prostheses face issues such as rapid wear, limited range of motion, and inadequate retention of the core between plates, leading to insufficient resistance to wear and tear and poor adherence to vertebral bone.
Innovation Solution
The design features upper and lower plates with inner curved surfaces and a core that allows sliding movement, incorporating projections and recesses for secure retention, along with textured surfaces and fins for enhanced attachment to vertebrae, and a flexible tie member or threaded rod for maintaining core position during movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If peripheral ribs and channels are provided to retain the core between plates, then the core retention is improved, but the bearing area is reduced leading to rapid wear
Solution Approach 1:
The core is divided into multiple segments or portions that can independently engage with the plates. Each segment provides retention functionality while the overall core structure maintains adequate bearing surface area, resolving the contradiction between core retention and wear resistance
Solution Approach 2:
The invention transitions from two-dimensional peripheral retention features (ribs and channels at the edge) to three-dimensional engagement throughout the core structure. Multiple engagement points are distributed across the core volume, providing retention without sacrificing bearing area
2Ease of operation
If keys and grooves are used to allow sliding movement in one direction, then the sliding capability is improved, but the orthogonal movement is restricted
Solution Approach 1:
The core is segmented into multiple portions that can move independently relative to the plates. This segmentation allows the core to accommodate complex multi-directional movements while maintaining controlled engagement, enabling both sliding capability and adaptability
Solution Approach 2:
The engagement system transitions from static key-and-groove constraints to dynamic multi-point engagement. The core portions can shift positions and orientations during movement, allowing adaptive response to various motion requirements while maintaining stable engagement
3Device complexity
If the core is merely clamped between the plates, then the assembly simplicity is improved, but the retention security is insufficient
Solution Approach 1:
The core is divided into multiple segments that independently engage with the plates through dedicated engagement features. This segmentation provides secure retention through distributed engagement points while maintaining relative assembly simplicity
Solution Approach 2:
The core portions are nested within the plate structure through interlocking engagement features. The core segments fit within recesses or engage with protrusions on the plates, providing secure retention while maintaining a compact integrated assembly
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
This configuration enhances the durability and stability of the prosthesis by allowing a larger range of motion while ensuring secure retention of the core, promoting better adherence to vertebral bone through bone growth and improved load distribution.
Implementation Method 1
a core between the plates, the core having upper and lower curved surfaces complementary in shape to the inner curved surfaces of the plates to allow the plates to slide over the core
Data Source
AI summary
A prosthetic disc for insertion between adjacent vertebrae includes upper and lower plates, a core disposed between the plates, and at least one projection extending from at least one of the upper and lower curved surfaces of the core into at least one recess of one of the inner surfaces of the plates. The recess is oversize with respect to the projection to allow sliding movement of the plate over the core while retaining the core between the plates during such sliding movement. The projection(s) may include a rod extending through an axial hole in the core, multiple surface features of the core, or the like.