Deformable Intervertebral Cage for Spinal Fusion

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Solution Overview

Problem

Current spinal fixation devices, such as static bone plates, often cause graft stress shielding, graft overloading, subsidence, and graft failure due to excessive strain or inadequate strain on bone grafts, leading to complications like fibrous tissue formation, bone resorption, and pseudarthrosis during vertebral arthrodesis and fusion procedures.

Innovation Solution

A deformable intervertebral cage with a superior and inferior member and a posterior member that allows for elastic deformation, providing load sharing and minimizing stress shielding and micro-motion, while being designed to fit within the disc space to avoid irritation of critical anatomical structures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If static bone plates are used for spinal fixation, then spinal stability is provided, but graft stress shielding and graft overloading occur leading to graft failure

Engineering Contradiction:

Improvespinal stabilityVSAvoidgraft reliability

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The cage is designed with dynamic characteristics that allow it to deform elastically under load, transitioning from static plate fixation to dynamic load-sharing. The cage body can compress and deform to accommodate spinal motion while maintaining stability, preventing both stress shielding and overloading of the bone graft.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The cage utilizes material parameter changes through elastic deformation, where the cage's stiffness and load-bearing capacity can dynamically adjust based on applied forces. This allows the cage to share loads appropriately with the bone graft during different phases of spinal loading, optimizing both stability and graft reliability.

Inventive Principle:

Principle #35Parameter changes

2Strength

If static components are used in cage-plate implants, then structural support is provided, but stress shielding and micro-motion lead to pseudarthrosis

Engineering Contradiction:

Improvestructural supportVSAvoidfusion reliability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The cage incorporates dynamic elastic deformation capabilities that allow controlled micro-motion while maintaining structural integrity. This dynamic behavior prevents excessive micromotion that would cause pseudarthrosis while preserving enough motion to stimulate bone formation and fusion.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The cage body functions as a flexible structural element that can elastically deform under physiological loads. This flexibility allows the cage to accommodate spinal motion and distribute stresses uniformly, preventing stress shielding while maintaining adequate structural support for fusion.

Inventive Principle:

Principle #30Flexible shells and thin films

3Stability of the object's composition

If the cage extends out of the disc space, then structural stability is improved, but irritation of esophagus and surrounding tissue occurs causing dysphagia

Engineering Contradiction:

Improvespinal stabilityVSAvoidtissue irritation

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The cage is segmented into distinct functional zones: a compressed cage body that remains within the disc space for stability, and separate superior/inferior members that can be configured to minimize tissue contact. This segmentation allows the stable portion to remain contained while reducing harmful effects on surrounding structures.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The cage design utilizes dimensional optimization by confining the main body within the disc space boundaries while using the superior and inferior members to provide stability in different orientations. This dimensional strategy maintains spinal stability without extending into the space where dysphagia-causing irritation would occur.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 deformable intervertebral cage facilitates vertebral arthrodesis and fusion by reducing stress shielding and micro-motion, promoting bone integration and fusion while maintaining spinal stability, thus preventing complications like pseudarthrosis and bone resorption.

Implementation Method 1

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentEP2967900B1Intervertebral cage

Publication Date: 2023.10.04 REVIVO MEDICAL LLC

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AI summary

The present disclosure provides an intervertebral cage including superior and inferior members each including an engagement surface for engaging a corresponding vertebrae. The intervertebral cage also includes a posterior member that extends between a posterior end of the superior and inferior members and spaces them from each other in a superior-inferior direction. The superior and inferior members extend in a posterior-to-anterior direction from the posterior member and define anterior free ends to form a substantially open anterior end between the superior member and the inferior member in a posterior-anterior direction. The engagement surfaces of the superior and inferior members substantially diverge from each other in the superior-inferior direction along the posterior-to-anterior direction. The superior and inferior members each include first apertures extending therethrough in the superior-inferior direction that define a pathway through the intervertebral cage in the superior-inferior direction.