I mean, I saw this guy who had both legs amputated. He entered the Utah Summer Games in the 100 meters in the "open" class, meaning he was taking on the best in the state straight up - no "handicapped" class. He took first in the preliminaries and second in the final.
If he thinks of himself as an athlete, he still is. But if he wants to play footsie under the table with his SO... that's something he lost.
So it depends to some degree on where your sense of personhood is. But I think for all of us, we're not a brain in a vat. We interact with our external physical environment. If you lose all of that... haven't you lost something that matters to you? If you can't enjoy a steak, can't enjoy a kiss, and can't enjoy the smell of a flower (or even the sight of one), then aren't you something less than you were when you could do all those things?
All right, let's tackle it a bit more directly than replacement: Does amputation of a limb diminish an individual's personhood? Is your answer dependent on the use of a prosthetic?