As I mentioned earlier, Parker has developed an infection around the implants in his leg. In itself this isn't life-threatening, but it is pretty uncomfortable, especially when stuff oozes out of his leg.
So, tomorrow he's having the implants out. And while he's under anesthetic, the surgeon will also remove a fatty cyst from his neck—also not dangerous, just uncomfortable.
The surgeon, his regular vet, and I all agree that this is Parker's last surgery. No matter how healthy he seems right now, at 12½ he hasn't got a lot of years left. But removing the steel from his leg and cleaning out the infection (which could well be a biofilm) will make his last few years a lot more comfortable.
I'll post an update when Parker comes home Thursday morning.