I just had surgery, last week, to remove some basal cell carcinomas from arms and chest. I wasn't sure what I'd be wearing for the surgery, since it was all just on my upper body.
When I arrived at the hospital, I was led to a space with a bed and curtains around it. The nurse told me to undress, take of everything, (she was adamant about everything off, and no jewelry, just my unadorned body,) and put on the gown laid out on the bed. She pulled the curtain closed.
I did as told, listening to the other patients in the other curtained off spaces around me. I couldn't tie the gown, so it was just resting on my shoulders. The nurse did it up for me, but just up at the back of the neck. The back was still opened, but I was in bed and they wheeled me to the pre-surgery area like that. I was unconscious by the time I reached the operating room, and not sure if the gown remained on, but it was on when I woke-up after.
After that, I was only wearing a gown for the time in the hospital, for a couple days. The gowns were uneven in the back, with the slit being more over to my left side. I thought this provided better coverage, even if left untied, but I found that still I was exposed if it wasn't held together. Most of these gowns were plenty long enough, for me at 6ft., but once I got one that must have been a small size, it only covered to just below my waist. Reminded me of a few times when that's happened at a physical.