I haven't read through the comments but I had a horse that did this same thing.
We had him checked for stifle and he was cleared of anything being wrong.
The shoer ended up crafting him a special shoe @ the school near here. It basically was a regular shoe with small plate welded onto the toe, with growing room. He looked quite the franken-horse. The idea was the extra weight + extra length beyond his toe would teach him to pick his foot up like he should.
Unfortunately, he ended up passing away after only his 2nd shoeing with that shoe of a freak accident, so I can't tell you if it ended up working as planned or not. His toe was growing out from not being able to drag it directly anymore. I still have the shoe if you are interested in seeing it.
Edit: I just re-read your post and it seems that you are asking for specific ways to trim. I think I misunderstood and thought you were just asking what you can do about the problem in general. Sorry. I'll also add that my gelding that was doing this was wearing his hoof down very badly, otherwise he would have remained barefoot.
Some days it's not worth chewing through the straps.
Last edited by Shawneen; 05-27-2013 at 01:44 AM.