Improving internal model strength and performance of prosthetic hands using augmented feedback.
Ahmed W Shehata, Leonard F Engels, Marco Controzzi and 3 others
PMID 30064477WHAT IT FOUND
Audio feedback added to a muscle-controlled prosthetic hand helped healthy users adapt more and complete more grasp-and-lift transfers without breaking the object.
Speed did not change. It was a small lab test in able-bodied people, not amputees.
Key findings
01Audio feedback added to the myoelectric control improved trial-to-trial adaptation (1.2 ± 0.25 versus 0.75 ± 0.15) and made smaller control changes easier to detect (44.6 ± 10 degrees versus 58.5 ± 12.5 degrees).
02A measure of uncertainty in the user's internal model was lower when audio feedback was added to the myoelectric control (0.22 ± 0.11) than without it (1.8 ± 0.6).
03Audio feedback added to the myoelectric control increased successful transfers without breaking the egg (65 ± 12% versus 37.34 ± 19%), but transfer time did not change (8.3 ± 0.74 seconds versus 8.4 ± 0.65 seconds).
STILL TO COME
How it was doneWhat they foundWhat it means for OTs
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What it does not show
The study included only 14 able-bodied subjects, not amputees or powered prosthesis users. The audio feedback comparisons used the 7 subjects who tested both conditions, so the result rests on a small sample. The hand was controlled through a bypass splint, not a typical prosthetic socket, and the egg was a rigid test object with a preset break threshold. The no-audio condition was tested before the audio condition, so practice or exposure could have contributed, although the retest group did not show significant learning. Submovement results were available for only five subjects because the test object failed to record data for two others.
Declared interests
Funding came from the Natural Sciences and Engineering Research Council of Canada and the New Brunswick Health and Research Foundation. The supplied text does not state author conflicts.
The easy way to misread this
Do not conclude that adding audio feedback to myoelectric control improves prosthetic hand use for amputees. The participants were able-bodied subjects using a bypass-mounted robotic hand, and the paper says the results must still be confirmed in the target population.