Prosthetics that improve performance should be banned from the Olympics. If prosthetics become good enough that completely-natural athletes can't win medals, then athletes who haven't lost limbs (and aren't willing to have an "accident") will effectively be excluded from the sport.

Of course, this doesn't apply to prosthetics that don't actually improve performance or are completely irrelevant to the sport in question. It doesn't matter if a soccer player has a prosthetic arm as long as it weighs as much as his other one.

Prosthetics are fundamentally different from other sports equipment in that any athlete can use a given piece of equipment, but most athletes can't use prosthetics at all.