A microdissection study was carried out on ten injected, cleared human
sternal specimens. Three types of vessel were identified that have th
e potential to carry blood to the sternum after mobilization of the in
ternal thoracic artery (ITA): (1) branches of the ITA that supply both
the sternum and the pectoralis major (''sternal/perforating branches'
'), (2) branches of the ITA that supply both the sternum and an adjoin
ing intercostal space (''sternal/intercostal branches''), and (3) post
erior intercostal arteries that do not anastomose with an ITA branch b
ut continue past the ITA to reach the sternum. All three types of vess
el were found more frequently in the proximal than in the distal half
of the sternum. For sternal/perforating and sternal/intercostal vessel
s to function as collaterals after ITA bypass grafting, their short co
mmon trunks of origin must remain intact. The data support the recomme
ndation that the branches of the ITA be ligated as close as possible t
o the ITA itself to preserve collateral blood now to the sternum.