Shortening of the fourth/fifth metacarpals

Last revised by Mohammad Taghi Niknejad on 14 Jan 2024

Shortening of the fourth/fifth metacarpals (brachymetacarpia) and less commonly metatarsals (brachymetatarsia) is seen in a variety of apparently disparate conditions. 

Pathology

Etiology

Common causes 2:

Uncommon causes 2:

Isolated shortening of the 5th metacarpals has been described in a familial variant of type 1 diabetes mellitus 3.

Radiographic features

Plain radiograph

Hand x-rays readily identify the abnormality and can be assessed by drawing a line along the heads of the 4th and 5th metacarpals. If this line intersects the head of the 3rd metacarpal then shortening is deemed to be present. 

Thus, shortened 4th metacarpal is the key to this finding. It is known as the metacarpal sign. It is important to note that a positive sign can be seen in up to 10% of normal individuals 4.

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