|Year : 2016 | Volume
| Issue : 1 | Page : 127-128
Aseem Tandon, Rama Devi Gara
Department of Anatomy, Armed Forces Medical College, Pune, Maharashtra, India
|Date of Web Publication||22-Dec-2015|
Rama Devi Gara
Department of Anatomy, Armed Forces Medical College, Pune - 411 040, Maharashtra
Source of Support: None, Conflict of Interest: None
The sternal foramen is a well-known variant of the sternum that carries the risk of life-threatening complications like pneumothorax, injury to vital structures like pericardial and cardiac puncture during acupuncture. A foramen was found in one sternum during the routine bone study of bones of the bank which were secured in Department of Anatomy. It was oval shaped measuring 8.75 mm × 7.35 mm, present in lower one-third of the body of the sternum. Distance from a sternal angle was 68.06 mm and 25.26 mm from the lower end of the sternum. The sternal foramen is usually asymptomatic found incidentally on chest X-ray. Hence this variation should keep in mind while performing invasive procedures like sternal puncture for bone marrow aspiration to prevent life-threatening complications.
Keywords: Breastbone, sternal foramen, sternal punctures, sternum
|How to cite this article:|
Tandon A, Gara RD. Sternal foramen
. Med J DY Patil Univ 2016;9:127-8
| Introduction|| |
The sternum or Breast bone has three components. The broad triangular manubrium which has a central jugular notch between two oval fossae for the articulation of sternal end of the clavicle, laterally it has an articular facet for first rib and demifacet for second rib. The elongated body which has articular demifacet for second rib and seventh rib at superior and inferior angles respectively, a complete facet for the articulation of third to sixth rib. The slender xiphoid process is continuous with the lower end of the body at the xiphisternal joint.
The sternum is derived from a pair of vertical mesenchymal bands on ventral body wall called as sternal bars. Chondrification occurs cranio-caudally in the sternal bars to form a cartilaginous model of manubrium, sternebrae of body, and xiphoid process. Failure of fusion of these sternebrae results in a sternal foramen which is more common at the level of third and fourth sternebrae.
Overall prevalence of sternal foramen by Babinski et al. was 10.5% in multi-detector computed tomography,  Stark 4.3% in chest computed tomography,  Cooper et al. 6.7% in autopsy cases.  Mostly asymptomatic, incidentally found in X-ray which may be confused with gunshot wounds or lytic lesions. 
| Observation|| |
During a routine bone study in the Department of Anatomy, we found an oval shaped sternal foramen in the lower one-third of the body of the sternum as shown in [Figure 1].
Measurements of sternum were taken with the help of Vernier caliper and found that the size of foramen was 8.75 mm × 7.35 mm, distance from sternal angle was 68.06 mm, and distance from lower end of sternum was 25.26 mm.
| Clinical Consideration|| |
Foramen in sternum can be misinterpreted as acquired lesions like a gunshot wound, fracture, lytic lesions, etc. As sternum is closely related to mediastinal structures, sternal foramen leaves the lung, heart and great vessels unprotected while performing invasive procedures like bone marrow aspiration,  acupuncture leading to life-threatening complications such as pneumothorax and cardiac tamponade. 
| Discussion|| |
The sternum begins to develop by mesenchymal bands on either side of the midline. These later fused to form a cartilaginous model of manubrium, sternebrae, and xiphoid process. Arrangement and number of ossification centers may vary according to the level of completeness, time of fusion of sternal plate and to the width of the adult bone. The manubrium is ossified from one to three centers which appear in the 5 th fetal month. First and second sternebrae ossify from the single center at an around 5 th fetal month. For third and fourth sternebrae, a pair of ossification centers for each appears in 5 th and 6 th fetal month respectively. The xiphoid process begins to ossify after birth around 3 rd year. Any failure or incomplete ossification may result in a sternal foramen. 
Sternal foramen is generally associated with sternal sclerotic bands. Other variations of sternum include double ended xiphoid process and single xiphoid foramen.  Cleft sternum due to the failure of midline fusion of sternum leaves the heart and great vessels unprotected also associated with craniofacial hemangioma and omphalocoele. 
The incidence of the sternal foramen is 4.3% in living and 6.7% in autopsy cases.  Most of the foramina located in the lower part of the body. Mostly foramen are isolated developmental anomaly but sometimes may associated with accessory fissures on left lung.
Size of sternal foramina ranged between 2 and 16 mm with a mean of 6.5 mm. Sternal foramen found in our routine bone study measured 8.75 mm × 7.35 mm, distance from a sternal angle was 68.06 mm, and distance from the lower end of the sternum was 25.26 mm.
In more than 50% of patients, direct adjacent structure dorsal to sternal foramen was the lung. Hence it is important to know the safe threshold for needle depth before proceeding for an invasive procedure. According to Grossner safe depth for needle insertion is not more than 2.5 cm. 
| Conclusion|| |
As sternal foramen is the most common variant and it is mostly asymptomatic. Serious complication after sternal puncture such as cardiac tamponade, and pneumothorax should be kept mind before performing an invasive procedure like a bone marrow biopsy, acupuncture, etc. It is advisable to take an X-ray to rule out such variations of the sternum.
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