Intervertebral Disc Prosthesis Core Sliding Friction
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Solution Overview
Problem
Existing intervertebral disc prostheses face difficulties in core sliding due to material constraints and design, leading to rapid wear and increased risk of prosthesis ejection from the spine, which is undesirable for patient health.
Innovation Solution
The intervertebral disc prosthesis comprises a first and second plate with a mobile core, featuring a curved surface for contact with the first plate and a flat surface for contact with the second plate, along with limit stops and a protective shell to facilitate smooth sliding and prevent excessive friction, while the core's design includes holes and grooves for lubrication and improved movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the core is allowed to slide freely relative to the plates, then the prosthesis can absorb movement constraints, but the sliding causes rapid wear and increases the risk of prosthesis ejection
Solution Approach 1:
A lubricating layer is introduced as an intermediary between the core and the plates. This lubricating layer facilitates smooth sliding to allow constraint absorption while preventing direct contact between the core and plates, thereby reducing wear and ejection risk
Solution Approach 2:
The friction parameter between the core and plates is changed by introducing a lubricating layer. This reduces the coefficient of friction to enable smooth sliding for constraint absorption while preventing excessive friction that would cause wear and ejection
2Reliability
If limit stops are added to prevent excessive movement, then prosthesis ejection is prevented, but friction increases and sliding becomes difficult
Solution Approach 1:
The lubricating layer acts as a mediator between the limit stops and the core. It allows the limit stops to prevent excessive movement while reducing friction during normal sliding operations
Solution Approach 2:
The contact interface is segmented into multiple regions: the lubricating layer for smooth sliding, the limit stops for preventing excessive movement, and the protective shell for structural support. This segmentation allows each element to perform its specific function without interfering with overall operation
3Reliability
If a protective shell is added to the core, then wear is reduced, but the shell may contact the limit stop and increase friction
Solution Approach 1:
The protective shell is designed with specific local properties: it covers the core surfaces that require protection from wear while leaving the limit stop contact areas exposed or properly configured. This local differentiation allows the shell to protect against wear without interfering with the sliding function
Solution Approach 2:
The lubricating layer serves as an intermediary between the protective shell and the limit stops. It prevents direct contact between the shell and limit stops, thereby reducing friction while maintaining the protective function of the shell
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 design enhances the core's ability to move freely and absorb constraints, reducing wear and the risk of ejection, thereby improving the prosthesis's longevity and positioning accuracy within the spine.
Implementation Method 1
the interstitial liquid from surrounding tissue can play a lubricating role to improve the sliding of the core on the substantially flat surface of the second plate
Data Source
AI summary
The disclosure relates to intervertebral disc prostheses, which may comprise at least three pieces including an upper plate, a lower plate, and a core mobile at least relative to the lower plate, the upper surface of the core being in contact with at least a part of the lower surface of the upper plate. Various embodiments have limit stops allowing friction to be limited, while limiting or preventing the movements of the core relative to the lower plate, in translation and in rotation, respectively, along an axis substantially parallel to the lower plate and about an axis substantially perpendicular to the lower plate, and have at least one hole disposed along the lower surface of the core facilitating sliding of the core relative to the upper surface of the lower plate with which it is in contact. Instruments for inserting intervertebral prostheses are also disclosed.