I don't know if there is possibly other information somewhere in the Legendarium concerning Elrond's healing powers, but there are two brief comments in the first chapter of the second book of FotR, "Many Meetings". First concerning Elrond:
Quote:
Elrond is a master of healing...
...there was some fragment of the blade still in the closed wound. But it could not be found until last night. Then Elrond removed a splinter. It was deeply buried, and it was working inwards.
|
That suggest to me that it was a kind of spiritual battle that Elrond fought; the fragment had to be located before it could be removed. How that was done remains a mystery - it must have some kind of surgery, but we do not read of a subsequent wound, so it must have been a special ability indeed.
The other comment refers to a special resistant quality in the Hobbits:
Quote:
And it seems that Hobbits fade very reluctantly. I have known strong warriors of the Big People who would quickly have been overcome by that splinter...
Your heart was not touched, and only your shoulder was pierced; and that was because you resisted to the last.
|
Add to that what the Warden of the Houses of Healing said about Merry in Minas Tirith:
Quote:
|
They are a very remarkable race. Very tough in the fibre, I deem.
|
As so often in real life as well, it seems that Frodo's healing was a combination of a very skilled physician and a patient with a strong will to survive.