The same thing happens to humans.

Many years ago I had back surgery. Within 4 months I had an infected suture come to the surface. Time goes by, and another one came up and one day I just flicked it off. Then a few years later another one surfaced. This one was also infected. It's now been over 10 years since that last one, so I guess I'm safe.

These were all nylon sutures that were supposed to stay inside. Some of us, dogs and gals, just don't like them I guess.