Your question gives too few details, so it's likely that multiple novels will match. Here's a stab nevertheless.
Perhaps you are thinking of the science fiction novel Prelude to Foundation by Isaac Asimov, first published in 1988.
In part of this story, Hari Seldon is worried about the recent popularity of the political leader Laskin Joranum who wants to overthrow the empire. He uses his son Raych to infiltrate in the movement and spy on that leader and his friends. Raych will have to act as if he was an honest supporter of Joranum. Raych gets surgery to change his appearance and voice so that Joranum doesn't recognize him. It would turn out that she sees through the disguise, but doesn't let Raych know this.
I do not recall if bone lengthening or shortening was involved specifically, and I the novel doesn't go into the details of the surgery.
If that novel isn't what you're looking for, you might try to browse TVTROPES WARNING the TvTropes page for the trope "Magic Plastic Surgery".