Metacarpal bones

The metacarpals form a transverse arch to which the rigid row of distal carpal bones are fixed.

The peripheral metacarpals (those of the thumb and little finger) form the sides of the cup of the palmar gutter and as they are brought together they deepen this concavity.

The middle metacarpals are tightly united to the carpus by intrinsic interlocking bone elements at their bases.

The body (shaft) is prismoid in form, and curved, so as to be convex in the longitudinal direction behind, concave in front.

It is broader, and extends farther upward, on the volar than on the dorsal aspect, and is longer in the antero-posterior than in the transverse diameter.

[5] Intraarticular fracture-dislocations of the metacarpal head or base may require surgical fixation, as fragment displacement affecting the joint surface is rarely tolerated well.

In anatomic Latin, adjectives like metacarpius,[13] metacarpicus,[14] metacarpiaeus,[15] metacarpeus,[16] metacarpianus[17] and metacarpalis[12] can be found.

Left hand shown with thumb on left.
The principle of homology illustrated by the adaptive radiation of the metacarpal bones of mammals. All conform to the basic pentadactyl pattern but are modified for different usages. The third metacarpal is shaded throughout; the shoulder is crossed-hatched.