Updates in Targeted Sensory Reinnervation for Upper Limb Amputation
Jacqueline S. Hebert
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Kate Elzinga
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K. Ming Chan
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Jaret Olson
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Michael Morhart
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K. M. Chan Division of Physical Medicine and Rehabilitation, Centre for Neuroscience, 5005 Katz Group Centre, University of Alberta
,
Edmonton
, AB T5R 2E1,
Canada
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K. Elzinga Division of Plastic Surgery, University of Alberta
, 2207-8210 111 St NW,
Edmonton
, AB T6G 2C7,
Canada
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J. S. Hebert (&) Division of Physical Medicine and Rehabilitation, Glenrose Rehabilitation Hospital, University of Alberta
, Rm 1239, 10230-111 Ave,
Edmonton
, AB T5G 0B7,
Canada
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M. Morhart Division of Plastic Surgery, University of Alberta
, 303 East Tower, 14310 111 Ave NW,
Edmonton
, AB T5M 3Z7,
Canada
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J. Olson Division of Plastic Surgery, University of Alberta
, 82-8440 112 St NW, 2D3 WMC,
Edmonton
, AB T6G 2B7,
Canada
Advanced robotic devices capable of simulating the dexterous ability of the upper limb with an array of internal sensors have raised the enticing prospect of replacing the lost intricate functions of the arm following upper limb amputation. However, a large gap still exists in the application of this technology to the human user. In particular, the ability to provide physiologically relevant sensory feedbackto have the amputee feel the prosthetic hand as their ownhas not yet been achieved. Although a number of different approaches are being investigated, targeted sensory reinnervation, a refinement of the original targeted muscle reinnervation procedure, is the most recent and promising development in the effort to create a functional human-machine interface with a closed loop sensory feedback system. This technique aims to reestablish hand sensation on the skin so that it can be readily accessed non-invasively during functional tasks. Recent efforts are being directed towards distributing hand maps widely on the stump without interference of sensations from the native area. In this article, we will review the surgical approaches that have been used for sensory reinnervation in upper arm amputation and compare the resultant outcomes and potential functional utility of the techniques.
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Despite major advances in engineered technology,
proximal upper limb amputation remains one of the most
difficult challenges for prosthetic replacement. Individuals with
proximal levels of arm amputation have a higher rate of
rejection of prostheses in comparison to more distal levels
of amputation [1, 2]. Reasons for rejection are widely
varied. The main concerns from myoelectric users that
limit use of the prosthesis include poor durability, poor
dexterity, and lack of sensory feedback [3].
In response to these concerns, artificial limbs with up to
22 degrees of freedom have been developed in an attempt
to design a natural limb replacement device with greater
function [46]. However, despite the existence of
multifunctional prosthetic limbs and efforts to deploy these into
clinical practice, challenges with implementation include
difficulties attaching the device to the patient, insufficient
motor control strategies to control the additional degrees of
freedom, and lack of sensory feedback from the device to
the human operator. Advances are being made with novel
socket designs to improve comfort and suspension [7], and
there is ongoing research into percutaneous skeletal
attachment to allow direct connection of the prosthesis to
the skeletal system [8]. Emerging motor control strategies
such as pattern recognition algorithms are promising in the
potential ability to control multiple actions of the prosthetic
limb [9]. However, designing a method to restore natural
sensation from the prosthetic limb is still an unsolved
challenge in the effort to restore dexterous hand function
following upper limb loss.
Developing a neural humanmachine interface that
receives and decodes sensory information is a difficult task.
The importance of natural, physiologic sensation cannot
be overlooked when attempting to restore sensory function
to an artificial limb. Various types of sensory feedback
from prosthetic devices have been trialed in the past [10,
11] but with no success in clinical translation or long-term
usage. This is likely because substitution methods had to be
usedthat is, the amputee would have to be trained to
understand that an unnatural (or non-physiologic) stimulus
meant that something of importance was happening to the
prosthesis. This form of sensory substitution can work in
controlled settings; however, it has not lead to long-term
adoption. The basis for rejection of the feedback device
may be that it does not tap into natural sensory mechanisms
or provide a percept that enhances the feeling that the
prosthesis belongs to the individual as their own hand.
Neural interfaces in both the peripheral and central nervous
system have been developed as a method to provide
sensory feedback. Peripheral nerve stimulation, as a
mechanism for restoring sensory information from the prosthetic
device to (...truncated)