I think Farland damaged his hand because he wasn't doing the one finger tremolo correctly or at least safely. The way he describes it in his book creates a lot of excess tension because he plants all of the fingers on the head, if you look at people like Yamashita, I only bring up Yamashita, a classical guitarist, because he mastered the technique same as Fred Bacon. Only difference is I don't think there are any videos of Fred Bacon doing it so we can't know how he accomplished it. Yamashita accomplished it by floating the hand keeping it free of tension. Same thing with flamenco guitarists. Not sure if I'm young enough to actually accomplish mastery of the technique, but I shall try by floating the hand or only planting the pinky.