Necrosis is a term medical students love to use.
It means the death of part of the body through lack of blood. Obviously the verse is something to do with Lent. But it is not a cutting off of the flow of blood in our mortal body by asceticism, fasting, self denial, and all that we have imagined Lent should be. So I read on quickly to the end of the Epistle to see if there are any clues to this principle of death and life. That is often taken to mean the self-denial of not living for our own benefit but for his.