Head

Guardian UK: No, there hasn’t been a human 'head transplant', and there may never be - Neurosurgeon Sergio Canavero is in the news again, claiming to have performed the first successful human head transplant. But even cursory analysis reveals that he hasn’t. And scientific logic suggests he never will

So, it was a successful procedure, if you consider paralysis, lack of consciousness and a lifespan of less than a day as indicators of “success”.