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August 19, 2019
Vertigo

New Technology Restores Movement and Sensation in Upper Limb Amputation Patients

Highlights:

  • Despite several advances in prosthetic limbs, a fundamental problem remains: amputees must deal with the fact that they are unable to feel with their artificial arms or hands.
  • While using a prosthetic limb, amputees must closely watch their own movement and the position of that limb at all times to avoid errors in movement such as overreaching.
  • Novel device able to turn on patient’s sensation of movement to control their bionic arms better with ability to perform finer movements and multi-task better while using the limb.

Breakthrough
in restoration of movement sensation in
amputees with bionic arms could help these persons better manage activities

of daily living, be more independent and improve quality of life.

The
study was led by Paul Marasco, Ph.D. Cleveland Clinic, and his team who have
engineered the technique to help amputees feel movement of their prosthetic
arms. The findings of this “first of its kind” appears in the journal Science Translational
Medicine
.

‘New technology of restoring upper limb movement sensation helps to integrate the prosthesis better and make the bionic arms feel more like “self.”’


“By
restoring the intuitive feeling of limb movement – the sensation of opening and
closing your hand – we are able to blur the lines between what the patients’
brains perceived as ‘self’ versus ‘machine’,” said Marasco, head of the
Laboratory for Bionic Integration in Cleveland Clinic’s Lerner Research
Institute. “These findings have important implications for improving
human-machine interactions and bring us closer than ever before to providing
people with amputation with complete restoration of natural arm function.”

Aim of the Study

By
feeling their missing hands while controlling their bionic prostheses, amputees
could produce complex grip patterns and perform
specific tasks equally well if not better
than able-bodied people.
To
improve the relationship between the mind and
the prosthesis, and make it function like a natural limb, the team investigated whether they could
employ illusory movement to help patients achieve better control over their bionic
limbs
.

Methods of the Study

  • The team studied six patients who had previously undergone targeted nerve reinnervation (TMR), developed as a novel strategy to improve control of myoelectric upper limb prostheses
  • When they vibrated the patients’ re-innervated muscles (by means of robotic devices) to provide illusory movement, these patients were not only able to feel the missing limb move but use this sensation to guide and control their prosthetic arm to perform movements more accurately and with better coordination.

Thus, the findings of the
study suggest that creating the
sensation of movement by strategic muscle vibration
, provided patients with
better spatial awareness and improved fine motor control without having to
constantly monitor the prosthesis. Also, this “movement
sensation” made the bionic arms feel like natural arms
.

Critical Difference
Between Normal Limb and Prosthetic Limb

When
a normal person moves his limb, the brain constantly receives feedback
regarding the movement’s position and progress. This unconscious mechanism
prevents errors in judgment,
like overreaching, and allows the body to make necessary corrections on time.

Amputees lose this
critical feedback,

however, and as a result, cannot control their prostheses without having to
constantly and carefully watch their movement and position of the prosthesis.

“When
you make a movement and then you feel it occur, you intrinsically know that you
are the author of that movement and that you have a sense of control or ‘agency’ over your actions,” said Marasco. “People who have had an
amputation lose that feeling of control, which leaves them feeling frustrated
and disconnected from their prosthetic limbs. The illusions we generate restore the sensation of movement and
re-establish their sense of agency over their prosthetics. This helps people
with amputation to feel more in control.”

Targeted Muscle
Re-innervation

Targeted
muscle reinnervation (TMR) was developed
as a novel tool to gain better control of myoelectric upper limb prostheses
.

During
this procedure, nerves found in the remaining upper arm or shoulder that had
earlier controlled the amputated portion of the arm and hand are transplanted
(reassigned) to a target muscle (e.g.: pectoral muscle), that is functional, but not able to
perform its primary function due to the amputation. These reassigned nerves
then gain control over the targeted muscle, which contract in response to brain
signals for the missing limb.

TMR
has been extensively studies in high-level upper limb amputations and has been
shown to improve functional prosthesis control.

Future Plans

The research team is
finding ways to expand these techniques in
patients who have lost a leg
, as well as neurological conditions that
affect sensation such as stroke.

The team plans to integrate the system into a prosthesis
for longer-term applications to help patients use it on a daily basis.

“The
ultimate goal of our research is to use movement sensation to streamline the
relationship between patients and their technology, to better integrate their
prosthetics as a natural part of themselves,” said Marasco.

In conclusion, if this prototype system becomes available
for routine clinical use, it could be a major achievement in improving the
quality of life and independence of the thousands of persons who have lost a
limb due to various causes.

References :

  1. Helping Amputees ‘Feel’ Through Their Artificial Arms – (https://www.lerner.ccf.org/bme/research/11.php)

Source: Medindia

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