myonecrosis vs sphacelus

myonecrosis and sphacelus both are nouns.

Word	Noun	Adjective	Verb	Adverb
myonecrosis	Yes	No	No	No
sphacelus	Yes	No	No	No

As nouns, sphacelus is a hypernym of myonecrosis; that is, sphacelus is a word with a broader meaning than myonecrosis:

myonecrosis: localized death of muscle cell fibers
sphacelus: the localized death of living cells (as from infection or the interruption of blood supply)

Other hypernyms of myonecrosis include gangrene, mortification, necrosis.

myonecrosis (noun)	sphacelus (noun)
localized death of muscle cell fibers	the localized death of living cells (as from infection or the interruption of blood supply)
	necrotic tissue; a mortified or gangrenous part or mass