When I was young, my piano teacher was then quite old (probably nearly as old as me

). The middle finger of his left hand suffered from a problem, maybe arthritis, which caused the tendon to shorten and this made his finger permanently fold up into the palm of his hand. When he really needed to use this finger he managed to play the note with the knuckle of the middle joint - he wasn't lightningly fast with it, and it worked best on black notes, but it was still very impressive, nonetheless.
My flute playing grandaughter had her left hand in plaster for a few weeks, so we played a duet of two on the same flute. She did the blowing and playing the right hand notes, and I played the left. You have to be really good friends to do this, as it is quite cosy

.
During the Napoleonic wars, a French flute-playing soldier by the name of Rebsomen lost his left arm and had a flute constructed that worked entirely off the right hand. The flute was held in a clamp and apparently he played conventional flute music brilliantly.