Myoelectric Prosthesis Control via Nerve Transfer and Adipofascial Separation
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Solution Overview
Problem
Current myoelectric prostheses for upper extremity amputees are limited by the inability to simultaneously and intuitively control multiple degrees of freedom due to a lack of available muscle signals, particularly for partial and total hand amputations, below elbow, and above elbow amputations, leading to restricted functional abilities.
Innovation Solution
The method involves novel muscle and nerve transfers, including transferring intrinsic hand muscles, forearm muscles, and nerves with their blood supply to allow signal detection by surface electrodes, enabling the creation of new signals for intuitive control of prosthetic functions through techniques like the STARFISH procedure, where all hand intrinsic muscles are transferred with their neurovascular pedicles to the dorsal aspect of the hand or forearm, and deeper forearm muscles are moved to superficial locations to enhance signal detection and reduce cross-talk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If surface electrodes are used to detect EMG signals from residual limb muscles, then myoelectric prosthesis control is enabled, but the number of detectable signals is limited due to limited available muscles
Solution Approach 1:
The patent segments the nervous system control by performing targeted muscle reinnervation (TMR) where individual nerves are transferred to separate muscle bellies. This allows each nerve to generate an independent EMG signal, transforming a limited number of muscle signals into multiple independent control channels. For example, transferring the median nerve to a specific muscle belly creates a dedicated signal for thumb opposition, while the ulnar nerve transfer creates another independent signal for finger flexion.
Solution Approach 2:
The patent adds a spatial dimension to signal detection by transferring nerves to superficial muscle bellies that can be easily accessed by surface electrodes. This dimensional repositioning allows non-invasive detection of signals that would otherwise require deep internal muscle access, thereby increasing the number of detectable signals without adding invasive sensors.
2Reliability
If deeper forearm muscles are used for signal detection, then signal reliability is improved, but signal cross-talk increases and detection difficulty increases
Solution Approach 1:
The patent uses adipofascial flaps as intermediary barriers placed between adjacent muscle bellies. These flaps act as physical separators that prevent electrical signal cross-talk between neighboring muscles while maintaining the superficial positioning needed for easy electrode access. The adipofascial tissue serves as an electrical insulator that preserves signal integrity without requiring deeper muscle placement.
Solution Approach 2:
The patent creates locally optimized detection zones by positioning each transferred nerve's muscle belly in a specific superficial location with dedicated adipofascial separation. Each muscle belly is locally prepared with thinned overlying tissue and surrounded by separating flaps, creating optimal local conditions for signal detection while maintaining reliability through the localized barrier structure.
3Measurement precision
If multiple surface electrodes are placed to detect multiple signals, then control precision is improved, but the requirement for available muscles increases
Solution Approach 1:
The patent performs preliminary nerve transfers to create dedicated muscle bellies for each control function before prosthetic fitting. By pre-positioning the nerves and their target muscles in optimal locations with adequate separation, the system prepares multiple independent signal sources in advance, allowing precise multi-channel electrode placement without requiring additional natural muscles.
Solution Approach 2:
The patent changes the spatial parameters of the muscular system through surgical repositioning. Nerves are transferred to create muscle bellies at specific distances from the skin surface and from each other, optimizing the geometric arrangement for electrode detection. This parameter optimization allows multiple electrodes to detect distinct signals with minimal cross-talk, achieving high control precision.
4Adaptability or versatility
If nerve transfers are performed to create new signals, then the number of controllable degrees of freedom increases, but surgical complexity increases
Solution Approach 1:
The patent employs universal surgical techniques and standardized adipofascial flap constructions that can be applied across different nerve transfer scenarios. The same basic surgical principles and materials are used regardless of which specific nerves are transferred, reducing the complexity burden despite increasing the number of controllable functions. The modular nature of the procedure allows systematic expansion of 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
This approach allows for independent and intuitive control of multiple prosthetic functions, significantly increasing the number of detectable signals, enabling advanced prosthetic capabilities such as individual finger control, thumb opposition, and simultaneous control of wrist and hand movements, enhancing the functional abilities of amputees.
Implementation Method 1
Myoelectric prostheses rely on the detection of a signal produced by muscle contraction in the residual limb to power the terminal device
Data Source
AI summary
A method of transferring intrinsic hand muscles along with a respective nerve and blood supply; and allowing signal detection by a surface electrode is provided. The method further includes transferring muscles of a forearm along with a respective nerve and blood supply; and allowing signal detection by a surface electrode.