Coronal 2D reconstruction CT arteriogram of left shoulder. (AA: axillary artery; C: Coracoid process; R: 1st rib; SA: Subclavian artery). Arrow depicts prominent screw with associated pseudoaneurysm. The subclavian artery becomes the axillary artery at the lateral border of the first rib. The subclavian artery lies in a groove on the superior aspect of the 1st rib