This is not a glib, politically correct answer, but why does handicap really very often come into it? To me, the heart of what we do is cerebral, that is uneffected by physical ability; after that the physical actions are merely an expression of what we feel.
You will not need me to tell you that there are as many different handicaps as there are people, and although you mention the cause of yours, you do not say how it has effected you.
For example, quite obviously a sub with no lower body muscle control/strength will be unable to crawl to their Dom/me, but the key to crawling is that you approach in a humble and non-powerful way. This same mind set could be expressed in how the sub's body language as they pull themselves along the floor to their Dom/me or even push themselves. Outside of this lifestyle when move someone with physical impairment great care is taken with body language to ensure that that person does not feel disempowered, the reverse could apply when a Dom/me is handling a sub.
If a Dom/me has issues with fine muscle control then tying and untying knots could be tricky, but what is wrong with velcro? I can see that if the D has very little body strength or control then inflicting significant pain requires a little more creativity, but am I informed the careful use of a TENS machine is highly effective.
So I guess my point is that since physical handicap does not effect D/s mindset and in everyone's case the physical action is ultimately only an expression of that, it is a just a case of don't get hung up about the normal methods of expression but think outside of the box.
cariad
(written with a background of no physical handicap myself, but having spent a year working with and at times living with people with various degrees of physical handicap from moderate to totally debilitating.)