Implanted Electrode Array for Fatigue-Resistant Muscle Stimulation

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Solution Overview

Problem

Current motor neuroprostheses for individuals with spinal cord injuries face limitations in standing duration due to muscle fatigue, particularly in the vastus lateralis muscle, and existing stimulation methods fail to selectively activate deep muscles without also activating superficial ones, leading to reduced mobility and inconsistent performance.

Innovation Solution

A system with a multi-contact electrode array that provides sinusoidally-varying moments to independent, mutually agonist motor units, using a stimulator assembly to maintain a constant sum of moments across multiple electrodes, thereby reducing fatigue and improving muscle recruitment and selectivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If surface electrodes are used for stimulation, then ease of operation is improved, but selectivity of muscle activation deteriorates

Engineering Contradiction:

Improveease of electrode applicationVSAvoidselectivity of muscle activation

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The electrode array is divided into multiple independent stimulation contacts (e.g., 8 contacts) that can be independently controlled. This segmentation allows selective activation of different motor unit pools within the same muscle, enabling deep muscle activation without activating superficial muscles. Each contact can be targeted to specific fascicles or motor units, providing the selectivity that surface electrodes cannot achieve.

Inventive Principle:

Principle #1Segmentation

2Manufacturing precision

If percutaneous electrodes are used for stimulation, then selectivity of muscle activation is improved, but reliability deteriorates due to infection risk and migration

Engineering Contradiction:

Improveselectivity of muscle activationVSAvoidsystem reliability

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The electrode array is fully implanted within the muscle tissue (intramuscular placement), nesting the electrodes deep within the muscle belly without requiring percutaneous leads. This eliminates exit sites where infection could occur and prevents electrode migration by securing the electrodes within the muscle substance. The electrodes are positioned to stimulate specific motor units while maintaining high selectivity.

Inventive Principle:

Principle #7Nested doll (Nesting)

3Device complexity

If single muscle stimulation is used, then device complexity is reduced, but duration of action deteriorates due to muscle fatigue

Engineering Contradiction:

Improvesimplicity of stimulation systemVSAvoidduration of muscle contraction

Core Design Contradiction:

Device complexityVSDuration of action of moving object

Solution Approach 1:

The system segments the muscle into multiple independent motor unit pools that can be stimulated separately. By alternating stimulation between these segregated pools (interleaved or carousel stimulation), the system allows one pool to recover while another is active. This extends the overall duration of muscle contraction and delays fatigue onset, as demonstrated by the ability to maintain standing for extended periods.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system employs periodic alternation between different motor unit pools using interleaved or carousel stimulation patterns. Instead of continuous stimulation of a single pool, the system periodically switches between multiple pools, allowing recovery periods for each pool while maintaining overall muscle activation. This periodic action significantly extends the duration of effective muscle contraction.

Inventive Principle:

Principle #19Periodic action

4Duration of action of moving object

If multi-contact electrodes are used to stimulate multiple motor units, then duration of action is improved, but device complexity increases

Engineering Contradiction:

Improveduration of muscle contractionVSAvoidcomplexity of electrode array and control

Core Design Contradiction:

Duration of action of moving objectVSDevice complexity

Solution Approach 1:

The multi-contact electrode array serves multiple functions: it can selectively stimulate different motor unit pools, implement various stimulation patterns (interleaved, carousel, simultaneous), and adapt to different muscles and applications. This universal design allows the same electrode array to extend contraction duration through multiple mechanisms while maintaining a relatively compact and integrated structure.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 system enhances muscle contractions' duration and reduces fatigue by selectively stimulating multiple motor units, allowing for longer standing times and improved mobility by minimizing overlap between stimulation contacts and optimizing stimulation parameters.

Implementation Method 1

Methodology Applied

Scientific EffectElectrical stimulation: Electrical Impedance Tomography

Data Source

PatentUS9468753B2System and method for stimulating motor units

Publication Date: 2016.10.18 CASE WESTERN RESERVE UNIV

AI summary

Systems and methods are provided for stimulating motor units. An electrode array includes a plurality of electrodes configured to provide stimulation to respective motor units of a plurality of independent, mutually agonist motor units. A stimulator assembly is configured to provide a stimulation current to each electrode of the plurality of electrodes. The stimulation current is provided such that a sum of respective time-varying moments at the plurality of motor units remains substantially constant and non-zero.