Also called the metacarpal sign, shortening of the 4th and 5th metacarpals is present when a line drawn at a tangent to their heads intersects the 3rd metacarpal. The commonest causes areidiopathic, post-traumatic, Turner’s syndrome, pseudohypoparathyroidism, pseudopseudohypoparathyroidism and basal cell nevus syndrome. In this case an old fracture of the 5th metacarpal suggests the cause may be previous trauma. 

Image courtesy of Dr Donna D'Souza