Bane has had a rough life prior to becoming Gotham's Reckoning, in The Dark Knight Rises — but it could have been much rougher, judging from some newly released concept art and details about a deleted sequence from the film.
In particular, Bane could have had horrifying scars on his back, which require a prosthetic belt and cause some of the massive agony that he needs the drugs from his mask to counteract. In an interview with GQ, costume designer Lindy Hemming explains:
The thing that you should have seen during that sequence is [Bane] being injured in his youth. So one of the fundamental things about his costume is that he has this scar from the back injury. Even if he hasn't got the bulletproof vest on, he still has to wear the waist belt and the braces. In that scene in the prison, where he's learning to fight the same way Batman learned to fight, he's wearing an early version of his waist belt. It's showing support, but it's not the finished one he eventually wears. He's also wearing an early version of his gas mask, all glued together … If you look at the film, unless they've cut it-and I'm sure they haven't-there's a whole early section for Tom Hardy where he's fighting and being taunted by people. He's got chains on him, and he's standing on a wooden thing while people are attacking him. And in that scene, he's wearing a much more ragged, primitive version of the mask.
When told that that sequence was indeed cut from the movie, Hemming said:
Well that's an awful shame, but I suppose you have to cut things. I won't elaborate on it too much, because it isn't in the film, but there was another section that showed you why he had the mask and where it came from.
Separately, designer Sebastian Lochmann posted a couple of images showing early designs for Bane's back scars — which look a lot nastier than anything we saw on him in the actual film. Here they are, via Comic Book Movie: