SURGICAL ANATOMY OF THE PHRENIC-NERVE AND INTERNAL MAMMARY ARTERY

Dissection of the thoracic inlet was performed on 22 cadavers to deter mine the relationship of the phrenic nerve to the internal mammary art ery as it passes from lateral to medial behind the first rib. On the l eft the nerve was found to cross superior to the artery and then media l to it in 14 of 22 specimens; on the right this was found in ten of 2 2 specimens. In all other specimens, it crossed inferior to the intern al mammary artery. These findings demonstrate that there is no constan t relationship between these structures, and emphasize the need for ca ution when dissecting the internal mammary artery at or above the leve l of the first rib.