metacarpal vein vs vena metacarpus

metacarpal vein and vena metacarpus both are nouns.

Word	Noun	Adjective	Verb	Adverb
metacarpal vein	Yes	No	No	No
vena metacarpus	Yes	No	No	No

As nouns, metacarpal vein and vena metacarpus are synonyms defined as:

metacarpal vein and vena metacarpus: dorsal and palmar veins of the hand

metacarpal vein (noun)	vena metacarpus (noun)
dorsal and palmar veins of the hand	dorsal and palmar veins of the hand