What about using something like this? http://www.benefitsnowshop.co.uk/sho...&sectionId=493

Wouldn't stop thumb or wrist movement and you could deflate it to use the crutches and reinflate it later. You can then inflate it more at night etc etc and you should still be able to use the wheelchair with it.

I suppose you've done the traditional of hot water and epsom salts followed by a massage and bandage treatment. Or alteratively hot wax followed by bandage. As in shove the hand in hot water, stretch each finger as much as you can (easiest with 2 people, one to hold the wrist one to bend each finger) and then place a rolled up bandage into the fingers, or a sponge, or a flannel or something. My spasms are rock hard (as in we have broken fingers, thumbs etc when getting my splints on) but the hot water does seem to add something.