Sounds like the FIL doesn't want much contact, if any. Your most important relationship is with your DIL. You might alienate her if you push her to get her dad to be more involved with you and your family. I'd move on from him, ask of his well being occasionally and focus on your daughter in law. That's difficult enough in my experience.

Glad your mending. Had a patella injury its not fun! Good luck.

For the sake of not creating family bad blood, is it better to make an appearance Christmas Eve?

Some people are narcissists and they do not have any concept of the feelings or welfare of other people.

It is likely not a snub to you personally. He may not be capable of concerned or caring behavior.

And it appears he has treated your son well? There may come a time when this man is needed
to help our your son and your grandchildren. I would not alienate him.

... I've learned to lower my expectations from those people and now I am seldom disappointed.

I've also learned other people are incapable of change by my direct communication: they get huffy and defensive and we both get angina. Don't expect lemonade when you squeeze a turd.

I’m sorry this happened to you and for the disappointment over his reaction (or lack of reaction/sympathy).
But out of love your own son, I suggest being zealously careful about expecting things from his wife or his in-laws. He and his wife are not in a position to change her father’s personality. Marriage is complicated. Please don’t add stress to your son’s marriage over something he can’t control. It will only hurt you or him or both.

You may have no understanding of this man’s actual life: what he is juggling, what failures or disasters he has under the surface, what his family situation is like.
*His brain might just be wired differently — somewhere on a socially-inept scale, better at business or whatever his field is, but really bad with people.
*He could be going through cancer, loss of his own parents, marital problems, depression or mental health problems — in ways that keep him distracted, busy, etc.
*He probably never learned to reach out or be social through cards and phone calls. LOTS of people didn’t.

Some people are chaotically busy and incapable of managing their daily requirements, thinking about an in-laws injury might not make it through to the front burner.

But none of that applies here. And I assiduously avoid discussing this with my son or really anyone other than my husband, and only when we're alone.
From previous experience I don't expect much, but he was there when I was injured. He saw my wrist. And nothing. It's just not kind or nice.

So choose what makes sense to you.
Who needs Christmas together anyway? If no one else (such as your son) ends up with new obligations to travel / divide up their time due to rifts in the family.

(I spent most of 20 Christmases during my 30s and 40s both sad and frustrated at being expected to become a ping pong ball. It led me to hate the holidays I previously loved. No chance to relax — nothing but rushed travel, catching illnesses in airports, disappointing one person or another. My kid has only one childhood memory of having everybody that he cared about together at Christmas.)

maybe expected some type of checking in with you. OTOH, if you just see him at an occasional family dinner or get together and chat a bit, then I wouldn't expect a lot. He's probably asked your son how you're doing.

Hope you're doing well.