Variations in collateral contributions to the blood supply to the sternum

The blood supply of the sternum plays a major role in healing of the sternum after sternotomy. The sternal blood supply is derived mainly from the medial horizontal branches of the internal thoracic artery (ITA). The ITA is usually described as giving off sternal, anterior intercostal and perforating branches supplying their respective areas. The aim of the present study was to describe variations in the arterial branching pattern of collateral contributions to the sternum. The study was conducted on 30 fresh specimens of anterior thoracic wall in which cellulose acetate butyrate was injected into the ITA. The branches of the ITA in the first to sixth intercostal spaces were dissected and any additional artery supplying the sternum in each intercostal space was observed. In the present study, the ITA gave off non-collateral branches - sternal, anterior intercostal and perforating. The ITA was also found to have branches which divided into two to supply two destinations which could establish collateral flow to the sternum: (1). A sterno-intercostal branch (1-12 mm in length) divided and diverged in a Y or T shape. The medial limb supplied the sternum and the lateral limb supplied the adjoining thoracic wall, anastomosing with the terminal part of the posterior intercostal artery. (2). A sterno-perforating branch supplied the sternum either anteriorly or posteriorly before perforating and supplying the pectoral region and anastomosing with the thoracoacromial artery. This study reinforces the practice of ligating branches of the ITA close to its trunk as they have the potential to develop collateral blood supply. In the present study the posterior intercostal artery was at times found to supply the sternum directly or via its collateral branch and was named the persistent posterior intercostal artery.