Dave Meltzer has the story at Yahoo Sports:
UFC officials have confirmed that Lyoto Machida will need surgery on one of his hands, thus delaying the planned (light heavyweight) championship rematch with Mauricio “Shogun” Rua (18-4). Machida injured his hand during his controversial win over Rua during UFC 104 Saturday in Los Angeles.
White was hopeful to get the rematch in as soon as Jan. 2, when the company has one of its traditional major events of the year at the MGM Grand Garden Arena in Las Vegas. Rua had agreed to the date, but Machida's surgery eliminates whatever slim possibility there was that he would be fully recovered and ready in time for that date. Right now, it is not known when the fight would be able to take place.