Second Metacarpal

The second metacarpal (2nd metacarpal) is the long bone associated with the index finger, forming the human palm along with the other four metacarpals ^[1]. It is the longest of the metacarpals ^[7], divided into a head, shaft/body, and a base ^[2].

It is located between the distal carpal row, and the second proximal phalanx, with the first and third metacarpals located on its either side ^[6].

Second Metacarpal

The index finger metacarpal has two ossification centers, one for the shaft, and the other for the head. Being the first of all the metacarpals to start ossifying, ossification begins at the middle of its shaft, around the 8th or 9th week of fetal development. The head of this bone begins to ossify at around the third year of life ^[3].

Second Metacarpal X-Ray Image

The base or proximal end of this bone has a convex, notch-shaped surface that forms articular facets for the distal carpal bones trapezium, trapezoid, capitate, and laterally, the second metacarpal. At its head or distal end, it articulates with the proximal phalanx of the index finger (second proximal phalanx) ^[4].

Metacarpal fractures are one of the most common types of bone fracture, though the second metacarpal is rare. Fractures in the palm bones can be classified into a fracture of the base, shaft, and head (relatively rare), with the second metacarpal being one of the most common sites for a head fracture ^[5].

Carpometacarpal arthritis is another condition likely to affect the joint between the second metacarpal and the bones of the distal carpal row. However, it is not as common as the thumb CMC joint arthritis.