From what I remember most of the experiments where more material based like healing a bone, or replacing a joint, or some sort of implant. So you could have things interfere, but it wasn’t like drug trials which would effect the entire body.
Orthopedic surgeons break bones all the time. It sounds cruel, but when done in a medical context, it's not so strange. It was a surgical procedure, it's not like someone dropped a rock on an awake pig.
You can’t really. You test in naive animals when critical, but repeating an experiment or needing a quick binary read-out, you can use non-naive successfully.
