Bone screws that get loose

On Monday night, I dreamt that I had some large black screws made of plastic. You could screw them in without needing a screwdriver, just by turning the head with your fingers. I was considering using some of them to hold my clothing in place by putting the screw through the fabric and into the bone of my arm or leg. This seemed like it would be very easy to do -- again, I wouldn't even need a screwdriver -- and I had no sense that it would be painful or cause bleeding or anything like that.

What made me reconsider this plan was the thought that if I put screws into my bones too often, inserting and removing screws from the same hole repeatedly, the hole would get slightly wider over time, and the screw wouldn't fit as tightly as before. Finally, they would just fall out. Therefore, I should only put screws into my bones when it's really necessary, not for trivial things like holding my clothing in place.

I think this dream was probably inspired by a cat scratcher my wife bought may years ago, broadly similar to the one pictured below, where to assemble it you had to drive plastic screws into thick corrugated cardboard. The screws always fell out after a while and had to be put back in, and the more that happened, the looser the screws became. That was years ago, though.

The next day, Tuesday, one of my adult students showed up with her arm in a sling. She had broken a bone in her shoulder about a year ago but had long since fully recovered, so I asked what had happened. She explained that one of the surgical screws used to repair her shoulder had somehow become loose, no longer fitting tightly into the bone, and so she had had to have surgery to replace it.