Velcro,
What a shame

.
I presume that she lies on her side ok? If so, the I would not foresee and particular issues with the actual farrowing,and she will not need to strain or use her legs.
I would suspect two main problems post farrowing.
1. There is a much higher chance that she will sit on some of her litter,as she is both less mobile and less able to see where they are. Also as she does not want to put weight on her legs, it is quite possible that she could simply "flop down" on the lots of them. Whilst I hate farrowing crates, in this case if this is likely to be a problem (and you can summise from how she currently gets her front end up and down) I would be looking to put a couple of strong hurdles either side for a couple of days to try and restrict her squashing ability.
2. If she can't stand, then pee and poo could be an issue for the piglets,presuming she will simply go half lying down maybe leaving this where the piglets are lying. I would make sure that this is being washed away regularly in the case of pee to stop acid on the navels and young skin of the piglets, and clear away poo frequently to reduce infection risks. Most pigs pee on getting up, and poo after their meals, so you may want to wash as you feed, and do a second round 1/2 hour after the first to clear poo away. Washing may include drying the area (jumble sale towels are our quickest way to dry an area, and lots of them!) and re-strawing after each meal.
Good luck, and let us know how you get on, as your experience may help someone else in future!