Stable, simultaneous and proportional 4-DoF prosthetic hand control via synergy-inspired linear interpolation: a case series.
Platon Lukyanenko, Hendrik Adriaan Dewald, Joris Lambrecht and 3 others
PMID 33736656WHAT IT FOUND
Two upper-limb amputees used implanted EMG to control virtual prosthetic hands with four movements at once.
They matched all 3-DoF targets and up to 100% of 4-DoF targets, with stability up to 10 months.
Key findings
01In initial EMG controller tests, S6 matched all targets averaging 2.69 ± 0.21 s/target and S8 matched all targets averaging 5.36 ± 0.46 s/target.
02S8's radial-ulnar 4-DoF controller initially matched 86% of targets averaging 10.94 ± 0.88 s/target, then improved in time to match targets and percentage of targets matched over 9 months.
03Using one repetition closest to the movement mean, S6's 3-DoF performance did not change and S8's time to match targets and path efficiency improved.
STILL TO COME
How it was doneWhat they foundWhat it means for OTs
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What it does not show
Only two subjects participated, and both had implanted EMG electrodes, so this does not show what happens for typical amputees or with surface electrodes. The task was matching virtual hand postures, not using a real prosthetic hand in daily life. The authors say it is unclear how the 4-DoF controller would perform in activities of daily living. Some 4-DoF controllers were later found to be missing training movements, so stability conclusions for those controllers are limited. The controller is not optimized and requires substantial computing resources. The algorithm assumes implanted EMG and may not work with surface EMG because rest signals may not be near zero.
Declared interests
Funders named are the Defense Advanced Research Projects Agency, the U.S. Department of Veterans Affairs, and the National Institutes of Health.
The easy way to misread this
Do not read this as evidence that the controller works in everyday prosthetic use. It was tested in two subjects in a virtual posture-matching task, and the authors say daily-life performance is unclear.