The formula that is used to calculate injuries was posted in the conferences, I bothered to dig it out once, but I am too lazy to do this now.
Either way, I am not interested whether it is 'impossible' or 'virtually impossible' to have +5 with any doctor level. Not much of a difference to me.
"I don't know half of you half as well as I should like; and I like less than half of you half as well as you deserve."