Metacarpals were the five bones connecting the wrist to the fingers and thumb. They were known collectively as the metacarpus.
In 2152, Phlox recorded the automated repair station's facsimile of Travis Mayweather's corpse exhibited signs of multiple thermal fractures on the right phalanges and metacarpus. (ENT: "Dead Stop")
In 2377, The Doctor, having downloaded his program into Seven of Nine's body, warned Harry Kim that he might fracture a metacarpal hitting the wall of a Lokirrim patrol ship. (VOY: "Body and Soul")