Intervertebral Disc Replacement With Curved Articulation Surfaces

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Solution Overview

Problem

Current intervertebral disc replacements, such as those with ball-and-socket joints, fail to provide effective motion attenuation, leading to accelerated degeneration of surrounding tissues due to end-motion impacts during various types of motion, and do not adequately limit motion ranges without causing tissue damage.

Innovation Solution

An intervertebral disc replacement apparatus that allows motion about three rotational axes, featuring articulation surfaces with specific geometries that increase intervertebral spacing as a smooth function of angular displacement, providing non-impact motion attenuation by ensuring a predefined minimum spacing and self-centering under axial loading, thus preventing end-motion impacts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a ball-and-socket joint is used in TDR, then a full range of motion in all directions is provided, but motion attenuation is not provided leading to end motion impact and tissue degeneration

Engineering Contradiction:

Improverange of motionVSAvoidend motion impact

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent employs spherical articulation surfaces with specifically designed curvatures that enable multi-directional motion while incorporating geometric features that progressively increase intervertebral spacing near the limits of motion. The spherical geometry provides the full range of motion capability, while the curved surface profile creates a self-limiting mechanism that attenuates end-motion impact through controlled distraction.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The invention changes the geometric parameters of the articulation surfaces, specifically designing the spherical surfaces with curvature radii and profile characteristics that cause intervertebral spacing to increase as a function of angular displacement. This parameter optimization allows the joint to provide full motion range while automatically attenuating impact forces near motion limits through the geometric relationship between surface curvature and spacing variation.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If flange impact is used to limit motion in ball-and-socket TDR, then motion range is limited, but repeated impacts cause degeneration of TDR and surrounding tissue

Engineering Contradiction:

Improvemotion range limitationVSAvoidtissue degeneration

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent incorporates a cushioning mechanism that activates before impact occurs. The spherical articulation surfaces are designed so that as the joint approaches its motion limits, the intervertebral spacing automatically increases, creating a gradual deceleration effect that cushions the approach to end position without sudden impact. This beforehand cushioning prevents tissue degeneration by eliminating repetitive impact loading.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The invention converts what would traditionally be a harmful impact force into a beneficial self-limiting mechanism. By designing the spherical surfaces with specific curvature characteristics, the natural reaction forces generated during motion automatically produce increasing distraction that limits further motion without impact. The force that would cause damage is transformed into a protective motion attenuation mechanism.

Inventive Principle:

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

3Adaptability or versatility

If axial rotation is allowed with minimal resistance in ball-and-socket joint, then full rotational motion is provided, but surrounding soft tissue and facets degenerate due to lack of motion attenuation

Engineering Contradiction:

Improveaxial rotation capabilityVSAvoidfacets and soft tissue degeneration

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The spherical articulation surfaces are designed with curvature characteristics that provide free axial rotation while simultaneously creating geometric constraints that limit excessive rotation. The curved surface geometry allows the ball to rotate within the socket with minimal resistance during normal motion, but as rotation approaches physiological limits, the increasing intervertebral spacing automatically attenuates further rotation, protecting surrounding soft tissue and facets from degeneration.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Data Source

PatentEP1986576B1Intervertebral disc replacement

Publication Date: 2012.04.11 FANEUIL INNOVATIONS INVESTMENT

Figure 1A~1D
Figure 2A~2C
Figure 2D~2E

AI summary

An intervertebral disc replacement has two members attached to vertebral body endplates of two adjacent vertebrae. The two members are formed with respective articulation surfaces which form at least part of an articulation arrangement. When loaded with compressive axial force, the articulation arrangement supports the vertebral contact surfaces against the compressive force to ensure a predefined minimum intervertebral spacing, and allows a range of turning motion in all directions. The articulation arrangement is formed to provide an increase in the intervertebral spacing as a smooth function of angular displacement from a neutral position over at least part of the range of motion in each direction for each direction of motion, thereby providing motion attenuation and restoring forces.