Myoelectric prosthetic arms nowadays represent a rather stale technology that remains getting built mostly according to the schematics of the sixties.
It remains being sold at absolutely screaming prices, and we are continuously told that the very complex wiring and mind boggling technology actually warrants prices of 45'000 to 120'000 for one prosthetic arm of that type, despite its clear and massive functional deficits. However, cars with loads of highly evolved technology sell for such prices, and cars are built and sold under free market assumptions (where build a car for, say, 1500 CHF and selling it for, say, 25000 CHF, would be absolutely in order).
But myoelectric arms never saw that type of technological break through. As that and as of today, that technology should be avoided by users (with only a few exceptions). And not surprisingly, rejection rates remain rather high: in terms of function and overuse prevention, one might be better off not wearing a myoelectric arm. It is surprising to see how little the industry, how little researchers and how little prosthetic technicians overall seem to care by, say, addressing the issues in a manner that does in fact address the issues that this technology not only has, but, always had.
After all, a colloquial slang expression saying "myo arms with hard sockets suck" does not quite nail it now, does it. Because more literally, they don't. Hard suction sockets do not work well as they may slip off, lose electrode contact, restrict motion and can be painful to wear, localized surface EMG is problematic as it tends to be unreliable due to a range of reasons including sweat, hard socket slip and others, and energy consumption as well as component stability lead to a poor overall performance. Read up on it elsewhere.
And yet, for over seven decades, mechanic, robotic and engineering labs have been mesmerized with the myoelectric arm concept. Institutions of all kind realized that portraying a prosthetic hand on their annual report or logo would attract funding. So they found that taking funding that was actually dedicated for health and rehabilitation could be branched off into their own funds if they played that card right. To this day, however, not much came out of this. Nothing at all, really, if one is to examine the papers that were written back in the days and then examine what is being sold and built today. And when the best thing I can buy still is a body powered arm with a hook [how it works][performance], clearly, the last 7 decades of prosthetic arm research point to one thing as a necessary step: there needs to be tight control over these projects.