The narrowed part in the middle is referred to as the body or shaft of the bone.

The bone is somewhat flatten giving it two surfaces; the plantar (towards the sole of the foot) and the dorsal side (the area facing upwards while standing).

[2] The second Plantar interossei muscle originates from the medial side of the base and shaft of the fourth metatarsal.

[2] The horizontal head of the adductor hallucis also originates from the lateral side of the metacarpophalangeal joint and from the deep transverse metatarsal ligament,[2] a narrow band which runs across and connects together the heads of all the metatarsal bones.

This article incorporates text in the public domain from page 274 of the 20th edition of Gray's Anatomy (1918)