Originally Posted by YertyL
Well, there is a slight difference. Anakin was able to survive some serious burns just long enough for a medical team to arrive after Obi-Wan had left him for dead. Sion is able to immediately stand up again in a fight, even if his opposite is trying to kill him. That's like Obi-Wan slashing at Anakin, and instead of dropping to the flour with 3 less appendices Anakin happily continues the fight. I cannot see how any Force power should make one's arms regrow after they have been cut off or something similar.
He didnt make his arm re-grow though... as the doctor said on the harbinger 'his spine is shattered, I don't know whats holding him togeather'. So he wasn't regrowing anything he was just putting back togeather the things that had broken. He was just holding his body togeather.