Anisotropic Spinal Connecting Elements for Targeted Motion Control

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Solution Overview

Problem

Conventional spinal stabilization techniques cause tissue trauma, scarring, and prolonged recovery due to the need for extensive tissue repositioning and exposure, and they provide uniform stabilization across all planes of motion, which is not optimal.

Innovation Solution

The use of elongated connecting elements with anisotropic cross-sectional shapes that define distinct moments of inertia about different bending axes, allowing for targeted resistance to bending in specific planes of motion, and are positioned and secured using minimally invasive surgical techniques with specialized inserter instruments to maintain precise orientation relative to the spinal motion segments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional spinal stabilization techniques are used with uniform rods, then stabilization is provided in all planes of motion, but tissue trauma and scarring increase due to extensive exposure and repositioning

Engineering Contradiction:

Improvestabilization effectivenessVSAvoidtissue trauma

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The rod is designed with anisotropic cross-sectional geometry where different regions have different moments of inertia about different bending axes. This allows the rod to provide differential stabilization - greater resistance in planes requiring more support and lesser resistance in planes requiring more motion, matching the specific needs of different spinal motion segments rather than providing uniform stabilization in all directions.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The rod employs asymmetric cross-sectional shapes (such as oval, triangular, or I-beam configurations) where the distribution of material is intentionally uneven across the cross-section. This asymmetry creates different area moments of inertia about different centroidal axes, enabling the rod to be stiffer in one bending direction than in another, thereby providing targeted stabilization in specific planes of motion while allowing motion in other planes.

Inventive Principle:

Principle #4Asymmetry

2Ease of operation

If conventional spinal stabilization techniques are used with extensive tissue exposure, then access to the stabilization site is achieved, but recovery time increases due to tissue healing requirements

Engineering Contradiction:

Improvesurgical accessVSAvoidrecovery time

Core Design Contradiction:

Ease of operationVSLoss of time

Solution Approach 1:

The rod is inserted through a minimally invasive pathway where it is delivered nested within a delivery system or sheath. The rod may be compressed or bent during delivery to pass through a small incision, then expanded or straightened into its functional configuration once positioned. This nesting approach allows complex anatomical access without requiring large incisions or extensive tissue repositioning, thereby reducing tissue trauma and recovery time while maintaining surgical accessibility.

Inventive Principle:

Principle #7Nested doll (Nesting)

3Device complexity

If conventional uniform rods are used for spinal stabilization, then simple device structure is maintained, but inability to provide targeted stabilization in specific planes reduces effectiveness

Engineering Contradiction:

Improverod structureVSAvoidtargeted stabilization effectiveness

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The rod's cross-sectional geometry is specifically engineered with varying dimensions along its length or at specific locations to create predetermined moments of inertia about different bending axes. By changing the geometric parameters (width, height, wall thickness) of the cross-section, the rod achieves different stiffness characteristics in different planes, enabling targeted stabilization without requiring complex active control mechanisms.

Inventive Principle:

Principle #35Parameter changes

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 approach reduces tissue trauma and scarring by allowing for targeted stabilization, minimizing unnecessary motion segment stabilization, and enabling more efficient recovery by providing tailored resistance to different types of spinal motion, thus enhancing the effectiveness of spinal stabilization procedures.

Implementation Method 1

The connecting element includes an elongated body having a cross-sectional shape defining a first moment of inertia about a first bending axis and a second moment of inertia about a second bending axis that is orthogonal to the first bending axis

Methodology Applied

Scientific EffectMoment of Inertia: Moment of Inertia

Data Source

PatentUS7563274B2Surgical instruments and techniques for controlling spinal motion segments with positioning of spinal stabilization elements

Publication Date: 2009.07.21 WARSAW ORTHOPEDIC INC

AI summary

Elongated connecting elements include bodies having anisotropic cross-sectional shapes defining a first moment of inertia about a first bending axis and a second moment of inertia about a second bending axis that is transverse to the first bending axis. The connecting elements are positioned along one or more spinal motion segments and engaged to vertebrae with anchors with the first and second bending axes in the desired orientation relative to the spinal motion segments.