Purpose: To evaluate the variations of the sternum and provide the prevalence of sternal foramen and its anatomical relationships.
Methods: In this retrospective study, 544 subjects ranging in age from 18 to 95 years were evaluated. Sternal variations, prevalence of sternal foramen and its anatomical relationships to mediastinal structures were examined with the axial, sagittal and coronal reformat images of the patients who underwent thoracic computerized tomography.
Results: In 500 subjects, following sternal variations were found: sternal sclerotic band in 120 (24%), sternal cleft in 3 (0.6%), sternal foramen in 26 (5.2%), focal cortical notch and defect in 44 (8.8%) patients. The manubriosternal fusion was partial in 65 (13%) patients and complete in 112 (22.4%) patients. The sternoxiphoid fusion was partial in 201 (40.2%) and complete in 153 (30.6%) patients. There was no xiphoid process in 9 patients (1.8%; 29-51 years; mean age 38 years). Xiphoidal ending types were as follows: single-ended 361 (72.2%), double-ended 125 (25%), and triple-ended xiphoid 5 (1%) patients. The sternal foramen was adjacent to the lung in 13 (2.6%), to the pericardium of heart in 3 (0.6%), and to mediastinal fat in 10 (2%) patients.
Conclusion: The sternum is a very critical anatomic structure of the anterior chest wall with several variations that can be confused with pathologic conditions. Radiologists' familiarity with these variations is important for better radiologic evaluation in making differential diagnosis.
Keywords: Anatomic variation; Computerized tomography; Foramen; Sternum.