I hope you don't mind if I also added some insight in why upper limb prosthetics may be rejected. The article notes that one of the primary reasons is "limited functionality". Unfortunately I would say this is only a third of the current problems with our technology with upper limb prosthetics. As a practitioner I have found that one of the bigger problems with myoletric arms is the weight. They are just too heavy. When a prosthesis is suspended off of an arm the added weight just multiplies. Above elbow amputations make this even more of an issue over below the elbow amputations. The other problem with an upper limb in general (not exclusive to myoelectric) is the loss of touch sensation. An upper limb has to see what they are doing with the prosthesis because they don't have sensory nerves in the fingers of the prosthesis. That is why you still see a number of children who reject an upper limb prosthesis. They can feel with their "nub". They can't feel with a prosthesis. Last of all I would agree that current functionality is also a factor. Many patient's find the effort is too much to do simple tasks.

I also wanted to throw out my opinion about research into prosthetics in general. To be honest upper limb prosthetics is such a small area of the patient pool. It is true that most upper limb amputations are due to trauma. The other small percentages are usually either congenital or cancer. My main complaint/concern is where all the research money is going in the field of prosthetics. Lower limb amputations are 10 times more prevalent and have less inherent rejection. I feel we spend way more money on research for cases that are quite rare in the practicing world of prosthetics.