The little metacarpal (fifth metacarpal) is one of the metacarpal bones, found within the substance of the hand at the base of the little finger. It articulates with the hamate proximally, the ring metacarpal laterally, and with the proximal phalanx of the little finger distally.
The little metacarpal (4th metacarpal refers to the ring metacarpal)
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The little metacarpal can be felt running down from the knuckle of the little finger on the dorsum of the hand. It is also palpable laterally. The metacarpal head forms much of the substance of the knuckle when the finger is flexed.
The little metacarpal is similar in structure to the other metacarpals, possessing a head, shaft and base. The proximal surface of the base is different in that the medial aspect is non-articular and bears a prominent tubercle, pointing proximally. The lateral surface of the base bears a facet for articulation with hamate, whilst a lateral strip articulates with the ring metacarpal. The dorsal surface is triangular almost to the base, whilst the lateral surface is not as curved as the other metacarpals and only inclines dorsally at its proximal end. This lateral surface is divided by a ridge separating palmar and dorsal interossei.
- The fourth palmar interosseous arises from the lateral aspect of the palmar surface
- The fourth dorsal interosseous arises from the lateral aspect of the dorsal surface
- The pisometacarpal ligament (the tendon of flexor carpi ulnaris) inserts into the palmar surface of the base
- Opponens digiti minimi inserts into the medial aspect of the palmar surface
- Extensor carpi ulnaris inserts into the dorsal surface of the tubercle.
In addition, dorsal, palmar and interosseous ligaments connect the little metacarpal to the other metacarpals.
The extensor and flexor tendons of the little finger are located on the dorsal and palmar aspects of the metacarpal, respectively.
- May be fractured