Son needs advice to do the right thing by his fiance's accident.?

My son's fiance has recently been involved in an accident while spinning. Long story short, she broke her neck in several places and is now in a motorized wheelchair learning to rehabilitate with it. I love my son very deeply and want him to be okay with his life but now he is on the fence about whether or not he should call off the wedding. Its not for 11 months anyway, so the time isn't an issue. I am worried that he needs to think and want him to make the decision that's right. I am no wordsmith so I am hoping to get some insight from the community in order to guide my son to do the right thing. I don't want him to spend his life in agony over a wife that he doesn't want to be with. I am hoping he decides to explain to her in simple terms that they are no longer the couple he had desired. How do I do that?