As selina_kyle pointed out, stretch out before trying it, my added advice would be, don't try to push it. Work your way back to flexibility you once had.
As for any concerns you might have, there may be dislocated disk slips in your spine and you'll be in need of getting someone to find you or to call an ambulance and then explain to them why you're in such position, depending as to where the slip happens, it might end up being permanent. So don't try to push it and just do it slow and steady to get back to the flexibility of it.
As for any concerns you might have if you do it slow and steady, there's basically none, other than a plus of being flexible overall.