The 23-year-old cast doubt on his participation in Milan after his Olympic triumph in Pyeongchang, saying repeatedly that healing the right ankle he injured in a training fall late last year was his priority.
"According to the results of a medical examination, I will be unable to take part in the worlds," Hanyu said in a statement, thanking his fans for their support.
"I will make every effort to recover as soon as possible through treatment and rehabilitation."
Last week, the double world champion told a news conference that he hoped to eventually successfully land a quintuple jump and break the five-spin barrier.