Answer:
Metacarpals are long tubular bones with an intrinsic longitudinal arch and a collective transverse arch. Bones are concave on the palmar surface and are joined proximally and distally by ligamentous attachments.
The second and third metacarpals are fixed rigidly at their bases, whereas the fourth and fifth carpometacarpal (CMC) joints are capable of at least 15° and 25° of motion, respectively. The thumb CMC saddle joint is highly mobile, and its unique motion and injury patterns are addressed more fully elsewhere (see Bennett Fracture and Rolando Fracture).
