Lot of misinformation in this thread please read.
It was not wood. It was his Susano'os sword, when Naruto first faces off against MAdara's Susano'o you can see it holding two swords. ALSO WHY THE TITLE OF THE CHAPTER IS CALLED THE SWORD OF HATRED. Madara stabbed her with his Susano'o sword of Hatred. How is this not obvious to everyone? Tsunade's kinjutsu (forbidden) is the regeneration technique which is forbidden because it shortens a person's lifespan. She could die due to using this technique and not by Madara I could see that happening.
So much misinformation was posted though.
It was not wood. It was his Susano'os sword, when Naruto first faces off against MAdara's Susano'o you can see it holding two swords. ALSO WHY THE TITLE OF THE CHAPTER IS CALLED THE SWORD OF HATRED. Madara stabbed her with his Susano'o sword of Hatred. How is this not obvious to everyone? Tsunade's kinjutsu (forbidden) is the regeneration technique which is forbidden because it shortens a person's lifespan. She could die due to using this technique and not by Madara I could see that happening.
So much misinformation was posted though.