The sternum in detail: a review of the anatomy and pathologies of the sternum

Abstract

The sternum and the sternoclavicular joints can exhibit a wide range of anatomical variations and serve as sites for numerous diseases, many of which are diagnosed solely through imaging studies. Recognizing these variations and differentiating them from pathological conditions is essential for radiologists, because accurate identification helps prevent misdiagnoses and treatment delays. This study provides a comprehensive review of the sternal anatomy, addressing anatomical variations, as well as mechanical, inflammatory, and traumatic pathologies, discussing their radiographic characteristics across different imaging modalities. Thus, it provides an overview of the key radiological findings.

Keywords: Magnetic resonance imaging; Manubrium; Multidetector computed tomography; Sternum; X-Rays; Xiphoid bone.

Figure 1

Normal anatomy of the sternum. Schematic drawing demonstrating the three sternal segments (manubrium, body, and xiphoid process), the clavicles, the first two ribs, the interclavicular ligament (1), the anterior sternoclavicular ligament (2), the sternoclavicular intra-articular disc (3), the sternoclavicular joint cavities (4), the subclavius muscle (5), the costoclavicular ligament (6), the costal cartilages (7), the radiated sternocostal ligament (8), the manubriosternal symphysis (9), the xiphisternal symphysis (10), and the articular facets for the ribs (11).

Figure 2

Sternal anatomy on MRI. A: Coronal T1-weighted image without fat saturation showing the intra-articular disc (1), the sternoclavicular joint (2), and the costoclavicular ligament (3). B: Coronal T1-weighted image, positioned more anteriorly in relation to image A, demonstrating the anterior sternoclavicular ligaments (4) and the sternocostal synchondrosis of the first rib (5).

Figure 3

Sternal foramen. A: Three-dimensional reconstruction from a coronal CT scan, showing a foramen in the sternal body (arrow). B: Axial CT scan, with bone window settings, demonstrating the characteristic “bowtie” appearance of the sternal foramen (arrow). C: Three-dimensional reconstruction from a coronal CT scan, showing a foramen in the xiphoid process (arrow).

Figure 4

Sternal foramen. A: Coronal T1-weighted MRI of the sternum with fat saturation, showing a foramen in the sternal body (arrow). B: Sagittal T1-weighted MRI of the sternum with fat saturation, showing a foramen in the sternal body (arrow).

Figure 5

Anterior curvature of the xiphoid process. Sagittal T1-weighted MRI of the sternum, showing a protruding xiphoid process (arrows).

Figure 6

Pectus excavatum. A: Sagittal T1-weighted MRI of the sternum, sagittal plane, with a dashed line representing the normal plane of the sternum. B: Axial CT of the chest, with bone window settings, with a dashed white line representing the normal plane of the sternum. The Haller index, obtained by dividing the transverse diameter of the thorax (T) by its anteroposterior diameter (AP), was 4.6 in this patient.

Figure 7

Pectus carinatum. A: Sagittal CT scan, with soft tissue window settings, showing anterior protrusion of the sternum (arrow). B: Three-dimensional reconstruction of an axial CT scan, with bone window settings, showing that the anteroposterior diameter of the thorax (AP) was greater than its transverse diameter (T) in a patient with pectus carinatum (Haller index of 1.48).

Figure 8

SAPHO syndrome. A: Coronal T1-weighted MRI of the sternum, showing costochondritis of the right sixth sternocostal joint (red arrow) and chronic manubriosternal arthropathy with bony irregularities and fatty replacement of its margins (white arrows). B: Gadolinium contrast-enhanced sagittal T1-weighted MRI of the sternum, showing enhancement related to right sternoclavicular inflammatory arthropathy (dashed circle).

Figure 9

Tietze syndrome. A: Coronal T2-weighted MRI with fat suppression, showing bone edema in the third and fourth sternocostal joints (dashed ellipse) and manubriosternal arthritis (arrows). B: Sagittal T2-weighted MRI with fat suppression, showing manubriosternal arthritis (arrows).

Figure 10

Acute sternal fracture. A: Sagittal CT scan of the chest, with bone window settings, showing a fracture with anterior misalignment (arrows) in the sternal body. B: Sagittal T2-weighted MRI of the sternum (of the same patient), with fat saturation, showing the fracture of the sternal body (white arrow) with impaction and bone edema (red arrows).

Figure 11

Septic arthritis. Gadolinium contrast-enhanced axial T1-weighted MRI with fat saturation, showing septic arthritis of the left sternoclavicular joint, with joint effusion, synovitis, and periarthritis. Note the enhancement of bone and adjacent soft tissue planes (dashed circle).

Figure 12

Osteomyelitis of the sternum. A: Coronal CT scan of the chest, with bone window settings, showing a lytic bone lesion (arrow). B: Axial PET/CT showing increased fluorodeoxyglucose uptake (dashed ellipse) in the same patient. The biopsy and culture results were consistent with a diagnosis of sporotrichosis.

Figure 13

Secondary sternal osteomyelitis with a collection in the anterior chest wall. A: Contrast-enhanced sagittal CT of the chest, with mediastinal window settings, acquired three months after surgical repair of an ascending aortic aneurysm, revealing a collection in the anterior chest wall (arrow). B: Contrast-enhanced axial CT of the chest, with bone window settings, showing the same collection in contact with the sternal sutures (dashed ellipse), where there is a separation between the bony edges (red arrow) at the manubrium, together with cortical irregularities, bone resorption, and increased density of retrosternal adipose tissue (white arrow). C: Contrast-enhanced sagittal CT of the chest, with maximum intensity projection reconstruction, obtained after a new debridement surgery, with a vacuum-assisted closure device (white arrow) and mediastinal drains (red arrows). Cultures confirmed infection with S. epidermidis.

Figure 14

Chondrosarcoma. A: Reconstruction of a contrast-enhanced sagittal CT scan of the chest, with mediastinal window settings, showing a bone lesion with aggressive characteristics in the sternum (arrow) and areas of calcification with a “ring-and-arc” pattern. B: Gadolinium contrast-enhanced coronal T1-weighted MRI of the same patient, with fat saturation, showing an area of necrosis within the lesion (arrow). Biopsy confirmed that this was a chondrosarcoma.

Figure 15

Hemangioendothelioma. Reconstruction of a coronal CT scan of the chest CT, showing aggressive lytic lesions throughout the body of the sternum and manubrium, with areas of rupture of the cortical bone (arrows). Histopathological examination confirmed the diagnosis of hemangioendothelioma.

Figure 16

Enchondroma. A,B: Chest CT, with bone window settings, in coronal and sagittal reconstructions, respectively, showing a sternal lytic bone lesion (red arrows), with calcifications characteristic of a chondral lineage lesion (white arrow), without signs of aggressiveness.

Figure 17

Sternal metastasis of breast carcinoma. A: Sagittal CT of the chest, with bone window settings, showing a heterogeneous, sclerotic lesion in the sternal body (arrow), with suspected secondary neoplastic involvement, in a patient with metastatic breast adenocarcinoma. B: Coronal CT of the chest (of the same patient), after surgical resection of the lesion (metastasectomy) with placement of a sternal body prosthesis (arrow).

Figure 18

Sternal closure with steel sutures after median sternotomy. A: Three-dimensional reconstruction of a coronal CT scan of the chest, showing the steel sutures (dashed ellipse) eight days after cardiac surgery, with well-approximated bone edges. B: Three-dimensional reconstruction of a coronal CT scan of the chest of the same patient six weeks after surgery, revealing dehiscence of the sternal suture at the central manubrium, with separation of the bone edges (arrow) resulting from a fluid collection in the anterior chest wall.