What is the primary reason for using a lateral projection of the sternum?

October 1, 2025 •

4 min read

According to imaging studies, a sternal fracture is most clearly visible on a lateral x-ray view rather than a standard frontal chest view. This is because the primary reason for using a lateral projection of the sternum is to obtain a clear profile image of the bone, allowing for the diagnosis of fractures and the assessment of any associated displacement.

Quick Summary

The main purpose of a lateral sternum x-ray is to visualize the breastbone in profile to identify fractures, dislocations, and bone infections like osteomyelitis. It is particularly valuable for showing the extent of fracture displacement following chest trauma, which is often obscured in frontal views.

Key Points

Detecting Fractures: A lateral sternum projection's primary purpose is to clearly identify sternal fractures, particularly those that are not visible on a standard frontal chest x-ray.
Assessing Displacement: The lateral view is the best plain film option for determining the degree of fracture displacement, which is crucial for evaluating injury severity.
Profile Visualization: By projecting the sternum in profile, this view avoids superimposition from the thoracic spine and ribs that can obscure the breastbone in other images.
Screening for Other Issues: It can also be used to evaluate for other sternal abnormalities, such as bone infections (osteomyelitis), metastases, or complications from sternotomy wires.
Guiding Further Imaging: Information from a lateral view helps clinicians determine if more advanced, higher-dose imaging, like a CT scan, is necessary to assess for critical internal injuries.
Standardized Technique: Precise patient positioning, including pulling shoulders back and using specific breathing instructions, is required for an optimal lateral sternum x-ray.
First-Line Tool: Despite the availability of CT, the lateral sternum x-ray remains a cost-effective and low-radiation initial diagnostic tool for suspected sternal injury.

Visualizing Sternal Fractures and Displacement

The primary reason for using a lateral projection of the sternum is to evaluate the breastbone for fractures, particularly after blunt chest trauma, such as from a motor vehicle accident or direct blow. Unlike a standard frontal (AP) chest X-ray, which is useful for assessing lungs and other thoracic structures but often has the sternum superimposed over the spine, the lateral view projects the sternum in profile. This orthogonal view provides a clear, unobstructed image of the entire length of the bone, enabling clinicians to identify breaks or cortical breaches that may otherwise be missed. For sternal fractures, especially those involving displacement or dislocation, which often occur along the sagittal plane, the lateral view is considered the gold standard for initial plain film investigation.

Assessing Displacement and Other Abnormalities

Beyond simply detecting a fracture, the lateral view is invaluable for determining the degree of anterior or posterior displacement. In severe trauma, a posteriorly displaced sternal fracture can pose a significant risk of damage to underlying mediastinal structures, such as the heart and major vessels. The lateral projection provides crucial information on the severity of the displacement, which helps guide clinical decisions regarding the need for further, more advanced imaging like a CT scan and the necessity of potential surgical intervention.

Other conditions that can be evaluated with a lateral sternal projection include:

Osteomyelitis: An infection of the bone, which may show up as changes in the bone's density or structure on a lateral view.
Metastasis: The spread of cancer to the sternum, which can also appear as a lesion on the radiograph.
Post-sternotomy concerns: For patients who have had open-heart surgery, the lateral view can help assess the status of sternal closure wires and look for complications like wire dehiscence or non-union.

The Technical Aspects of Lateral Sternal Radiography

For a high-quality lateral sternal image, precise positioning is critical to avoid superimposition of the ribs and other thoracic structures. The patient is typically positioned standing or sitting upright, with the affected side of the thorax adjacent to the image receptor. To achieve a true lateral view, the patient's arms are brought together behind their back, rolling the shoulders posteriorly and pulling the chest forward. Breathing instructions are also crucial; the technologist may ask the patient to take a deep breath and hold it during exposure to maximize clarity by minimizing motion blur. The specific technique used, including the voltage (kVp) and current (mAs), is adjusted to optimize visualization of the sternal bony cortex.

Comparison of Imaging Modalities for Sternal Evaluation

While the lateral sternum X-ray is an excellent initial tool, other modalities offer different advantages, particularly in complex trauma cases. CT scans, especially multidetector CT (MDCT) with multiplanar reconstructions, are widely considered the gold standard for diagnosing sternal fractures and associated injuries. Ultrasound can also be used as a quick, bedside tool to assess for fractures and other issues.


Imaging Modality	Key Advantage	Key Disadvantage	Primary Use Case
Lateral Sternal X-ray	Excellent for visualizing the sternum in profile to show fracture and displacement.	Can miss subtle, non-displaced fractures; lower sensitivity than CT.	Initial assessment for suspected fracture, especially after trauma.
Computed Tomography (CT)	Superior sensitivity and specificity; reveals associated injuries (hematomas, cardiac).	Higher radiation dose; can occasionally miss transverse fractures if axial cuts are used.	Trauma evaluation, complex fractures, and assessing internal injuries.
Ultrasound	Fast, radiation-free, portable bedside tool.	Operator-dependent; less reliable for assessing fracture displacement.	Quick confirmation of fracture at the bedside in the emergency department.
Oblique Sternal X-ray	Projects the sternum over the heart shadow for more uniform density.	Often less valuable than the lateral view for displacement.	Used in conjunction with the lateral view for additional detail.

The Role of Lateral Projection in Clinical Practice

The lateral sternal projection is a fundamental part of the radiographic workup for patients with suspected sternal injuries. According to a Medscape article, it is the preferred plain radiograph for making a diagnosis because the nature of these fractures often involves displacement in the sagittal plane. However, it is essential to remember that while the lateral view is highly effective for visualizing the sternum, associated injuries to the heart and lungs can be far more critical. For this reason, a lateral sternum X-ray is often just the first step in a broader assessment, especially in trauma settings, to determine if more sensitive imaging like a CT scan is necessary. The decision to use a lateral projection is guided by the patient's symptoms, the mechanism of injury, and the need for a clear, unobstructed view of the sternum to evaluate for fracture and displacement.

Conclusion

In summary, the primary reason for using a lateral projection of the sternum is to obtain an accurate profile view of the breastbone, which is essential for clearly identifying and assessing fractures and associated displacement following chest trauma. The lateral view overcomes the limitations of standard frontal chest X-rays, where the sternum is obscured by the thoracic spine and other structures. By providing a detailed sagittal-plane image, it allows clinicians to evaluate the extent of the injury and decide whether more advanced imaging or intervention is required. This targeted view is a critical component of initial radiographic examinations for blunt chest trauma, ensuring comprehensive diagnostic information for better patient management.

A Note on Advanced Imaging

In modern clinical practice, especially for severe trauma, a CT scan often supplements or replaces dedicated sternal X-rays due to its superior sensitivity and ability to detect associated thoracic injuries. However, the lateral sternum X-ray remains a valuable, lower-radiation, and readily available tool for initial assessment.

Frequently Asked Questions

A frontal chest X-ray is often insufficient because the sternum is superimposed over the thoracic vertebrae and other structures in the chest cavity, obscuring a clear view of the bone. A lateral projection is required to show the sternum in profile and avoid this obstruction.

The lateral view is most effective for visualizing sternal fractures, particularly those that involve displacement or dislocation, as these often occur along the sagittal plane.

A dedicated lateral sternum X-ray uses specific positioning and exposure settings focused solely on the breastbone to ensure the clearest possible image, minimizing superimposition from other structures. A standard lateral chest X-ray is broader and primarily assesses the lungs, heart, and mediastinum.

Besides fractures, a lateral projection can aid in the diagnosis of bone infections (osteomyelitis), metastatic disease, and issues related to sternal closure wires in post-operative patients.

If a fracture is highly suspected based on clinical findings, but a plain radiograph is negative, further investigation with a more sensitive modality, such as a CT scan, is often warranted.

While a CT scan offers higher sensitivity and is better for assessing associated internal injuries, a lateral sternum X-ray is a valuable, lower-radiation, and often sufficient initial tool for evaluating sternal fractures. The choice depends on the clinical context.

The X-ray procedure itself is painless. However, if a patient has significant chest trauma, the positioning required for a proper lateral view can be uncomfortable or painful. Technologists take precautions to ensure patient safety and minimize discomfort.