First, glad to read that you're getting better! I remember that you liked pushing weights - there are quite a few exercises that one can do while not using legs or having them rest. Not sure if that works with your specific surgery. I guess it would be like prison, can't move, so get to 1000 sit-ups or push-ups or whatever your legs allow. If they allow it.

Also, a friend of mine hiked up Machupichu at age 80. He was in incredible shape. Looked old, yes, but was still traveling and hiking and driving and thinking. He always led a very active life, never gave into "age appropriate" behavior. He told me once that he had sold his big motorbike because he was 80 now and had to take a step back, but the next day I saw him driving on it. When I asked him about it:

"Oh, yeah, that was the 800cc I sold, it was hard for me to lift it up. The 500cc works fine."