According to Albert Hash there was a banjo player in south west Virginia who as a child fell into a fire and burnt his hands so badly that the sinews were damaged which caused his fingers to curl inward.
This man went on to become very influential on the younger banjo players of the area.
If anyone in the UK gets to see the Whitetop Mountain Band on their tour here in September (and I reccommend that you do)you could check the story out with Albert's brother-in-Law Thornton Spencer, I believe his wife Emily was a pupil of the man in question.

Django Rheinhardt of course was another musuician who was unfortunate enough to damage his hands in a fire. He went on to develop a style of playing with the use of just two fingers of his left hand. Amazing.