User blog comment:Xilinoc/Ch. 616 - Mimihagi-sama/@comment-7805464-20150219124634/@comment-26091912-20150219220929

Well if we're to interpret it as literal, then why does Ukitake use the word 'hand'? Why not arm?

I think in this context, 'right hand' is a synonym for something essential to the SK: an actual body, alter ego, second-self, etc.

I don't think Ukitake implied that he'll sacrifice himself, just so the SK can gain a literal right hand on his torso. If what Ukitake said about sacrificing everything except his eyes is true, then my theory is that the SK will gain Ukitake's body, but will retain his own eyes.