The Cervical Rib

Abstract

A cervical rib is found in approximately 7 % of patients suffering from thoracic outlet syndrome; [1–3] although its incidence has been previously reported as high as 25–33 % [4–7]. It is an extra rib that originates at the level of C7 and then extends laterally and anteriorly, fusing frequently with the anterior scalene muscle or inserting on top of the first rib behind the subclavian artery (Fig. 26.1). The rib is not always a bony structure readily visualized radiographically. Often enough, there is only a short bony structure resembling a horn on the X-ray arising from the C1 transverse process. Thereafter, however, it exists as a very strong ligament extending all the way down to the top of the first rib. Physiologically, it works exactly as a completely ossified structure would. In 1869, Gruber proposed a classification of cervical ribs [8, 9] based on the amount of bone present and on the thickness of the rib like structure. (Fig. 26.2) The virtue of this classification it that it shows that, even when the radiographic exam only demonstrates prominence of the C7 transverse process, most often a strong fibrous ligament does actually extend from the tip of that process all the way to the top of the first rib, none of which can be visualized on the plain X-ray exam (Fig. 26.3).