Intervertebral Disc Prosthesis Rolling Contact Mechanism
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Solution Overview
Problem
Existing intervertebral disc prostheses suffer from localized friction, leading to premature wear and reduced lifespan, as they often restrict movement to anteroposterior displacement without allowing rolling motion along the edges, which limits their optimal functioning over time.
Innovation Solution
A disc prosthesis design featuring a circular periphery that enables rolling movement of the intermediate element along the edges, with a conical guide trajectory and a recess in the lower plate to absorb shocks, using high molecular weight polyethylene materials for reduced friction and improved durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the intermediate element is constrained to slide in a rail or recess, then the structure is simple and manufacturing is easy, but localized friction occurs at the contact edges leading to premature wear and reduced lifespan
Solution Approach 1:
The intermediate element is designed with a spherical cap geometry that enables rolling motion between the upper and lower plates. This curved surface configuration replaces the traditional sliding rail mechanism, transforming the contact mode from sliding friction to rolling contact, thereby eliminating localized wear at fixed edges while extending prosthesis lifespan
2Reliability
If the intermediate element is allowed to roll along the edges, then lifespan is extended by eliminating localized wear, but the device complexity increases
Solution Approach 1:
The spherical cap geometry of the intermediate element inherently provides the rolling mechanism needed to extend lifespan. This geometric feature allows the element to roll along curved trajectories defined by the guide surfaces, eliminating localized wear without requiring additional complex mechanical components or mechanisms
Solution Approach 2:
The prosthesis transitions from a static sliding constraint to a dynamic rolling motion system. The intermediate element can now follow curved trajectories and adapt its motion path, enabling multi-planar movements including flexion, extension, and rotation while maintaining low friction contact through continuous rolling rather than fixed sliding
3Device complexity
If only anteroposterior displacement is allowed, then the structure is simple, but natural movements like flexion, extension, and rotation are limited
Solution Approach 1:
The dynamic rolling mechanism enabled by the spherical cap geometry allows the intermediate element to follow curved trajectories in multiple planes. This provides natural flexion, extension, and rotation movements that mimic physiological spinal motion, significantly enhancing movement capability without requiring complex mechanical actuation systems
Solution Approach 2:
The spherical cap geometry naturally accommodates multi-planar movements through rolling contact. As the element rolls along curved guide surfaces, it can achieve flexion, extension, and rotational movements, providing physiological-range-of-motion adaptability while maintaining structural simplicity
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 extends the prosthesis' lifespan by eliminating localized wear points, allowing for natural movements like flexion, extension, and rotation, while minimizing friction and articular pain through rolling contact and shock absorption, thus maintaining the natural space between vertebrae.
Implementation Method 1
the periphery has a circular shape and is adapted to allow the rolling movement of the intermediate element along the edges
Implementation Method 2
the base of the intermediate element has an outer peripheral circular collar comprising several openings, so as to absorb the shocks between the edges of the guide and the collar by deformation of the said collar
Implementation Method 3
using high molecular weight polyethylene materials for reduced friction and improved durability
Data Source
Figure 1~4
AI summary
The invention relates to an intervertebral disc prosthesis consisting of: an upper plate (16), a lower plate (18) having an essentially-flat support surface, and an intermediate element comprising a base (22) which is equipped with a rim (23) and which is topped with a spherical cap (24). The upper plate and the cap define a ball and socket joint therebetween. The base of the intermediate element comes into contact with the support surface, while the lower plate (18) is equipped with a guide (28) comprising two edges (28a, 28b) which maintain the intermediate element therebetween. The rim of the base comes into contact with the edges (28a, 28b) and said rim is circular in shape and adapted to enable the intermediate element to roll along the length of the edges (28a, 28b).