Sorry but if my oignons turn to a point where they are sprouting, I just throw them out and make a mental note to buy new ones next time I'm in the supermarket.
Not that they ever reach that point with me... depending on what I cook I go through 1lbs of oignons in less than 2 weeks.
Tonight let us eat, drink and be merry for tomorrow we die.
The onion rots from the inside out.
The green thingy is the shoot - so you could, theoretically, plant it and have baby onions in about 3 months!
Once the onions have a green shoot, they begin to turn soft and sort of sickly. MUCH better to have a nice, crisp, fresh, white (or red!) onion...