Bifid rib

A bifid rib is a congenital abnormality occurring in about 0.2% of the population and there may be a female and right-sided predeliction. The sternal end of the rib is cleaved into 2. It is usually unilateral.

Usually it is clinically silent but it may present as a coincidental finding on chest radiography when there appears to be 8 vertebrae articulating with the sternum. A bifid first rib can be an uncommon cause of thoracic outlet syndrome.

(Note that very rarely a bifid rib may occur as part of Gorlin-Goltz syndrome or Job syndrome. It also has been reported as occurring in Kindler syndrome.)

Reference:

1. Andrea A, Tardieu G, Fisahn C, Iwanaga J, Oskouian R, Tubbs R. Bifid Ribs: A Comprehensive Review. Anatomy. 2016;10(3):221-7