Can't advise you on the surgical risks because I'm not a surgeon and risks are a matter of the surgeon having information about his own expertise and your unique situation. What I can tell you that experienced surgeons can and do go through the SAME CUT that was made prior and of course, they can also see your bone quality and prior cut in the scans to make a judgement call on the matter. I think it takes about a year for the bone cut to heal and the cut line gets strong enough to go through it again as long as they go through the same cut. Because you are nervous about this, my advice would be to just ASK the surgeon; 'Is my PRIOR bone CUT strong enough to cut through again?' It seems like the answer is 'yes' since he gave an OK. But it doesn't hurt to ask if this is something you are nervous about.