The Spaniard has struggled to find his form since joining the Serie A outfit on a season-long loan from Swansea City and is yet to score in three league outings for Rafael Benitez's men.
A stellar first season in south Wales saw Michu hailed as one of the bargains of the transfer window following his £2million signing from Rayo Vallecano in 2012, but ankle problems blighted his progress last term.
After netting two goals in 17 Premier League games, Michu was shipped out to Napoli on a temporary deal with a view to a permanent switch.
However, the former Celta Vigo man's ankle issues have returned and Napoli announced the forward had undergone a keyhole procedure on Thursday.
"Michu has undergone arthroscopic cleaning his right ankle in a clinic in Vitoria in Spain," read a short statement.
Napoli ensured their progression to the last 32 of the UEFA Europa League with a goalless draw at Sparta Prague on Thursday.