"Old age comes on suddenly, and not gradually as is thought." Emily Dickinson
What is considered medically necessary for the American insurance standard is whatever gets you from the bed to the toilet. I am not kidding. No other aspect of daily living other than using the bathroom is considered "necessary," which means your basic prosthetic given to most amputees—a stick with a rubber foot as a leg, or a stick with a hook on the end as an arm, has fundamentally not changed since WWII.
Gizmodo has a feature on Cyborg life this week. I can't verify the truth of this statement, but it sure feels true. If the insurance industry had an up-to-date standard for its work, maybe it wouldn't be so hard to get the use of a terrific technology like Bioness approved.