Relationship of Sternal Foramina to Vital Structures of the Chest: A Computed Tomographic Study

Sternal foramina are a well-known variant anatomy of the sternum and carry the risk of life-threatening complications like pneumothorax or even pericardial/cardial punction during sternal biopsy or acupuncture. There have been numerous studies numerous studies examinimg prevalence of sternal foramina, but the study of the exact anatomical relationship to intrathoracic structures has received little attention. In a retrospective study of 15 patients with sternal foramina, the topographical anatomy in respect to vital chest organs was examined. In most patients, the directly adjacent structure was the lung (53.3%) or mediastinal fat (33.3%). Only in three patients, the heart was located directly adjacent to a sternal foramen (20%). Theoretically, if the needle is inserted deep enough it will at some point perforate the pericardium in all examined patients. There was no correlation between the patient habitus (i.e., thickness of the subcutaneous fat) and the distance to a vital organ. In this sample, pericardial punction would have not occured if the needle is not inserted deeper than 2.5？cm. Given the preliminary nature of the data, general conclusions of a safe threshold for needle depth should be made with caution. To minimize the risk of hazardous complications, especially with sternal biopsy, preprocedural screening or image guidance is advocated. 1. Introduction Sternal foramina are a well-known variant anatomy of the sternum with reported prevalence between 4.3 and 6.7% [1, 2]. These foramina are developmental anomalies because of incomplete fusion of ossification centers; most often they are located at the caudal parts of the corpus sterni [3, 4]. In most cases, these foramina are isolated developmental anomalies [4]. Because of the close contact to the mediastinum and therefore vital structures of the chest, there is a risk of life-threatening complications like pneumothorax or even pericardial/cardiac puncture during sternal biopsy or acupuncture (Figure 1) [5, 6]. Figure 1: Computed tomographic images of a typical sternal foramen. The axial slices (b) are showing the close contact to vital structures (lung and heart). There is a potential risk of life-threatening complications (pneumothorax/cardiac tamponade), if a needle is inserted unintentionally through this foramen. There have been numerous studies examining the prevalence of sternal foramina. In contrast, the study of the topographical anatomy in respect to intrathoracic structures has received little attention. Only one morphological study reported that all needles which were inserted