While there seems to be some debate about whether Edgar Allan Poe's 1839 short story "The Man That Was Used Up" counts (even if it's listed as a genre story in ISFDb), it's clear there are some inarguably SF elements.
Although it's not made clear if his artificial leg and arm are fully functional (though it is hinted they are, since the text does not note a limp or any other impediment to normal movement), the general has at least two parts that are artificial and actually work as replacements for the lost body parts:
- A functioning artificial eye:
"O yes, by the way, my eye- here, Pompey, you scamp, screw it in! Those Kickapoos are not so very slow at a gouge; but he's a belied man, that Dr. Williams, after all; you can't imagine how well I see with the eyes of his make."
- An artificial voicebox:
Hereupon, the negro, grumbling out an apology, went up to his master, opened his mouth with the knowing air of a horse-jockey, and adjusted therein a somewhat singular-looking machine, in a very dexterous manner, that I could not altogether comprehend. The alteration, however, in the entire expression of the General's countenance was instantaneous and surprising. When he again spoke, his voice had resumed all that rich melody and strength which I had noticed upon our original introduction.