It’s easy. Nanomachines are like magic fairy dust. Once you realize just how very much story can be replaced by a simple drop of the word “nanomachines”, it’s easy to see why a science-fiction author would rely on it for all those tricky logistical questions. Even if it cheapens the story and causes the audience to roll their eyes, it’s no worse than the explanations given by fantasy stories and many other popular series.
— An article about Metal Gear Solid 4
CONCLUSION
The tiny robot surgeons will take out the titanium from KK’s back.