Your granddaughter used to live with you, but recently left suddenly and moved in with her boyfriend.
Your husband has dementia. Your son doesn't keep in contact with you or your husband.
You recently had a car accident and a fall without any contact or help from your son.
It sounds like you and your son have a troubled relationship for quite a long time. Yes, it would have been kind for him to be in touch with you, but there are clearly issues which are preventing him.
Maybe you need to step back for a little while, let things settle down and then approach him again. I'm not sure whether he and your DIL are still together - are you in contact with her at all? Maintain your relationship with your daughter and hopefully things will improve within the family.