Extensible Medical Lead with Co-axial Conductor Coils

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Solution Overview

Problem

Implantable medical leads used in neurostimulation systems face challenges due to the stretching and relaxing of the human body, which can lead to mechanical stress and inefficiencies in electrical conduction, particularly in systems like spinal cord and deep brain stimulation.

Innovation Solution

The development of extensible implantable medical leads with co-axial conductor coils, where an outer coil is disposed co-axially about an inner coil, both formed of insulated conductors, allowing the leads to stretch by at least 10% and return to their original length, with the outer coil having more conductors than the inner coil to match shear stresses and improve performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the lead is made extensible to accommodate body movements, then the lead can stretch by at least 10% and return to its original length, but the mechanical stress and inefficiencies in electrical conduction increase

Engineering Contradiction:

ImproveextensibilityVSAvoidelectrical conduction efficiency

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent employs a co-axial nested structure where an outer coil of insulated conductors is disposed about an inner coil of insulated conductors. Both coils are wound in the same direction and are electrically insulated from each other. This nested configuration allows the lead to stretch and relax while maintaining electrical conduction efficiency, as the co-axial arrangement distributes mechanical stress uniformly across both coils without compromising electrical integrity.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The lead incorporates a composite structure combining polymeric material for the lead body with co-axial coils of insulated conductors. The polymeric material provides extensibility to accommodate body movements, while the co-axial conductoral coils maintain electrical conduction. The combination of these materials and structures resolves the contradiction by allowing mechanical flexibility without sacrificing electrical reliability.

Inventive Principle:

Principle #40Composite materials

2Adaptability or versatility

If the lead is made extensible to accommodate body movements, then the lead can stretch by at least 10% and return to its original length, but the mechanical stress on the lead increases

Engineering Contradiction:

ImproveextensibilityVSAvoidmechanical stress

Core Design Contradiction:

Adaptability or versatilityVSStress or pressure

Solution Approach 1:

The co-axial nested structure with the outer coil disposed about the inner coil creates a distributed mechanical stress pattern. When the lead stretches, both coils expand uniformly in the co-axial arrangement, and when it relaxes, both coils return to their original configuration. This nested geometry ensures that mechanical stress is evenly distributed across the entire lead structure rather than concentrated at specific points, reducing the risk of mechanical failure.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The lead is designed with dynamic characteristics that allow it to repeatedly stretch by at least 10% and return to its original length through elastic deformation of the polymeric material and co-axial coil structure. The dynamic nature of the co-axial arrangement enables the lead to adapt to body movements while maintaining structural integrity and minimizing cumulative mechanical stress through reversible deformation.

Inventive Principle:

Principle #15Dynamics

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 enhances the extensibility and reliability of the leads, ensuring consistent electrical conduction and reducing mechanical stress, allowing for effective spinal cord and deep brain stimulation while accommodating body movements.

Implementation Method 1

The lead body is formed of a polymeric material that is extensible between a first length and a second length... allowing the leads to stretch by at least 10% and return to their original length

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

the outer coil having more conductors than the inner coil to match shear stresses and improve performance

Methodology Applied

Scientific EffectShear stress: Shear Stress

Data Source

PatentUS9220890B2Extensible implantable medical lead with co-axial conductor coils

Publication Date: 2015.12.29 MEDTRONIC INC

AI summary

An extensible implantable electrical lead includes a lead body having a proximal end and a distal end. The lead body is formed of a polymeric material that is extensible between a first length and a second length. A plurality of electrical conductors are disposed within the lead body and extend between the proximal end and the distal end. The plurality of electrical conductors are each electrically insulated from each other and form co-axial coils between the proximal end and the distal end. The co-axial coils include an outer coil disposed about an inner coil. The inner coil has a first plurality of electrical conductors that are electrically insulated and separated from each other and have a first coil diameter. The outer coil includes a second plurality of electrical conductors that are electrically insulated and separated from each other and have a second coil diameter. The second coil diameter is greater than the first coil diameter, and the first plurality is a number less than the second plurality.