"Doing it" normally refers to sex, and since this thread's topic is sex, naturally one would assume that is what you were referring to.
Your post quite clearly said you would find a way to do "it" (whatever this conveniently now means to you) with your partner (I take it this means your hypothetical wife, and not an outside partner?). There was no indication that she would actually *want* you crawling on her severely disabled body, or that it would matter to you whether she did or not, but rather a statement that you "expect" her to do the same if you were the one severely disabled. Does she not have a say?
The loss of a limb is not considered "severely disabled". Clearly, we are not picturing the same patient.
Maybe you should aim for a bit more clarity.