Artificial Spinal Disc with Compressive Spacer Supports

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Solution Overview

Problem

Traditional elastic spinal disc implants face failure due to detachment from vertebrae under tensile stress and material deterioration, as they are more susceptible to tensile loading than compressive loading.

Innovation Solution

An artificial spinal disc design featuring upper and lower members with spacer supports and elastic spacers positioned between them, where the spacers are compressed under tensile or compressive loading, reducing the risk of failure by minimizing tensile stress on the elastic materials.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If elastic material is attached to endplates that are affixed to vertebrae, then the disc provides shock absorption and approximates natural disc motion, but the elastic material may detach from endplates under repeated tensile stress

Engineering Contradiction:

Improveattachment reliabilityVSAvoidtensile strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent inverts the traditional load-bearing mechanism by using spacers that bear compressive loads rather than having elastic material bear tensile loads. The spacer is positioned between the endplates and vertebrae to absorb compression, while the elastic material is configured to minimize tensile stress exposure, thereby resolving the detachment issue under tensile loading.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the stress state parameter from tensile to compressive for the primary load-bearing component (the spacer). By designing the spacer to experience compression during physiological loading rather than tension, the system exploits the superior material properties of elastic materials under compression, thereby improving attachment reliability and reducing deterioration.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If traditional elastic discs are used, then shock absorption is provided, but the elastic material deteriorates under tensile loading through stress cracks

Engineering Contradiction:

Improvematerial durabilityVSAvoidtensile loading damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful effect of tensile loading into a beneficial compressive loading regime. By reconfiguring the load path so that the spacer bears compression rather than tension, the system transforms the previously harmful tensile stress that caused stress cracks into a beneficial compressive state where elastic materials exhibit superior durability and resistance to deterioration.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Strength

If elastic materials are used in artificial discs, then more shock absorption is provided compared to articulating discs, but the materials have more desirable properties under compressive loading than tensile loading

Engineering Contradiction:

Improveshock absorptionVSAvoidperformance under tensile loading

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent inverts the loading regime from tensile to compressive for the primary load-bearing spacer component. This allows the elastic material to operate in its more favorable compressive loading regime, maintaining superior shock absorption properties while avoiding the reliability issues associated with tensile loading.

Inventive Principle:

Principle #13The other way round (Inversion)

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 design enhances the durability and performance of the artificial spinal disc by ensuring the elastic spacers experience only compressive stress, thereby reducing the risk of detachment and deterioration, and providing improved shock absorption and motion similarity to natural discs.

Implementation Method 1

The spacer supports thus compress the first elastic spacer when the disc is tensilely loaded

Methodology Applied

Scientific EffectCompression: Compression

Implementation Method 2

The additional spacer is therefore compressed when the disc is compressively loaded

Methodology Applied

Scientific EffectCompression: Compression

Data Source

PatentUS7419506B2Artificial spinal discs and methods

Publication Date: 2008.09.02 HIGHRIDGE MEDICAL LLC

AI summary

An artificial disc includes a top vertebra-attachment portion and a lower spacer support connected to the top vertebra-attachment portion; a bottom vertebra-attachment portion and an upper spacer support connected to the bottom vertebra-attachment portion. The spacer supports are disposed between the vertebra-attachment portions, and the lower spacer support is disposed between the bottom vertebra-attachment portion and the upper spacer support. The disc further includes a first elastic spacer positioned between the spacer supports for compressively resisting tensile loading of the disc; and a second spacer disposed between the bottom vertebra-attachment portion and the lower spacer support or between the top vertebra-attachment portion and the upper spacer support for compressively resisting compressive loading of the disc.