Right, I dont think he can actually be torn to pieces. There's no official explanation for it on panel (at least not a very clear one), but his skeleton behaves like a single articulated piece. Hulk failed to pull his limbs apart and has acknowledged he lacks a way to kill him off for good.
Even if it was ripped off (and other people have disputed that), the metal doesn't inhibit cellular growth. It's adamantium beta: the by-product of fusing true adamantium to someone with his unique mutation.