Pushin' On: UAB Spinal Cord Injury Model System Digital Newsletter Volume 37 | Number 2 | Page 4

TECHNOLOGY WATCH
Next Step in Exoskeleton Technology
Powered exoskeletons have now been around for a
few years. These devices are used to help people with
paraplegia to stand and walk. It was limited to persons
with paraplegia because walking and standing required
the use of hands for crutches or a walker. Now the
technology is advancing for people with tetraplegia.
In a recent publication, French researchers described
how they first trained a man with tetraplegia to control
characters in a video game via the brain-computer
interface. Once practiced, he was eventually put into the
exoskeleton and the same mental techniques he used to
play the video game were used to control the exoskeleton
device. He controlled it using two WIMAGINE 64-channel
electrocorticography implants placed right on the surface
of his brain’s movement centers. The signals were then
decoded and translated into the movements of the
exoskeleton. The researchers noted that the man seemed
to move his legs much easier than his arms and hands.
Of course, this technology is still years away from
being an everyday device for people with paraplegia –
much less tetraplegia. But this is a major step in what is
to come the upcoming decades. It might even replace
wheelchairs as the primary mobility device for people
with spinal cord injury.
Transcutaneous Electrical Nerve Stimulation Sleeve
Transcutaneous electrical nerve stimulation (TENS)
works by delivering small electrical impulses through
electrodes that have adhesive pads that stick to a
person’s skin. For people with tetraplegia, these impulses
can trigger hand function to grasp objects, which is an
extremely useful function. The drawback is that TENS is
a limited use device. This means it is something that is
used only for short periods of time and not something
used throughout the course of the day. In fact, too
much use often leads to nerve fatigue.
Researchers have now developed a potential
solution. The technology relies on an arm sleeve
with an array of electrodes built-in, as well as
novel closed-loop neurostimulation techniques.
The system can accurately trigger multiple
muscle movements, at a consistent strength,
without leading to excessive fatigue. This was
achieved thanks to feedforward-feedback control
mechanisms that can normalize the grasp in
real-time and without causing unnecessary
discomfort.
In this study, two people with tetraplegic
demonstrated impressive finger extension,
flexing, and the ability to grab onto fairly large
things. This included grasping and lifting a 25
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uab.edu/sci
once water bottle, something that neither person is able
to do without the sleeve.
The researchers believe the technology has a future.
It might one day lead to a stand-alone wearable device,
or it might be possible to combine their neurostimulation
approach with brain-computer interfaces to generate
considerably more nuanced and better controlled
movements.