Isso é "O Extra" de Greg Egan.
Daniel Gray didn't merely arrange for his Extras to live in a building within the grounds of his main residence - although that in itself would have been shocking enough. At the height of his midsummer garden party, he had their trainer march them along a winding path which took them within metres of virtually every one of his wealthy and powerful guests.
....
Of course, naked, the Extras looked exactly like naked humans, but in Gray's cultural milieu, stark naked humans en masse were not a common sight, and so the paradoxical effect of revealing the creatures' totally human appearance was to make it easier to think of them as less than human.
....
When he awoke, he was numb all over, and unable to move or make a sound, but he could see. Poorly, at first, but over a period that might have been hours, or might have been days - punctuated as it was with stretches of enervating, dreamless sleep - he was able to identify his surroundings.
....
When, at last, one arm came under his control, he raised it, with great effort, into his field of view.
It was his arm, his old arm - not the Extra's.
He tried to emit a wail of despair, but nothing came out.
....
One day, he had a visitor - the first person he'd seen since the operation who was not a health professional clad in white. The visitor was a young man, dressed in brightly coloured pyjamas, and travelling in a wheelchair.
....
Then Gray realised that the man in the wheelchair was the Extra, D12. And yet he spoke. And when he spoke, the doctors shook with sycophantic laughter.