Anatomical and physiological background
The sternum is a flat spongy bone shaped somewhat like a dagger. Its structure comprises three main parts:
- Manubrium (upper section);
- Body (middle, most extended section);
- Xiphoid process (lower pointed part).
An important anatomical feature is the notches on the lateral surfaces. The clavicular notches for articulation with the sternal ends of the clavicles are located in the manubrium area, while the costal notches, to which the cartilaginous parts of the ribs attach, are located along the sides of the body.
The physiological role of the sternum is that it "closes" the rib cage anteriorly. This bone serves as a kind of shield protecting the mediastinal organs. For this exact reason, disruption of its integrity carries an extremely high risk of trauma to intrathoracic structures.
Injury mechanism and displacement biomechanics
In the vast majority of cases, bone integrity is disrupted as a result of the application of significant force — a direct blow to the chest area or powerful anterior-posterior chest compression. The most common scenario in clinical practice is a car crash where the driver strikes their chest forcefully against the steering wheel.
The typical fracture zone is the border between the manubrium and the body of the sternum, as well as the upper third of the body itself. This injury is characterized by a strictly defined pattern of bone fragment displacement:
- Proximal fragment (upper) is displaced anteriorly and moves downward.
- Distal fragment (lower) shifts posteriorly and moves upward.
This displacement configuration leads to the formation of a pronounced hematoma localized directly in the anterior mediastinal adipose tissue.
Complications and comorbid pathology
The classification of sternal fractures takes into account localization, presence of displacement, and associated complications. Injuries with significant posterior displacement of bone fragments pose the greatest danger.
They can provoke:
- Cardiac contusion — the most frequent and formidable complication, accompanied by hemorrhages into the pericardial and myocardial tissues, leading to severe cardiac dysfunction;
- Pleural injuries capable of causing a breach in the airtightness of the pleural cavities.
Isolated sternal injuries are relatively rare. As a rule, the shock wave leads to polytrauma, most commonly rib fractures in their cartilaginous (parasternal) zone.
Management of complicated chest trauma
Since chest bone fractures are frequently accompanied by internal organ damage, the surgeon must monitor the development of pneumothorax and hemothorax.
In pneumothorax: the drainage tube is removed only if air leakage does not resume for 3–4 days after complete lung re-expansion. If air continues to enter the pleural cavity under continuous suction for more than 7–10 days, this serves as a direct indication for surgery — exploration and suturing of the lung laceration.
In hemothorax: puncture and drainage placement are performed strictly in the 7th intercostal space along the posterior axillary line. Important rule: forced evacuation of large volumes of accumulated blood is strictly prohibited. A sharp drop in cavity pressure can provoke a resumption of bleeding from ruptured vessels. Emergency surgery is indicated if blood output exceeds 250 ml per hour continues after lung re-expansion.
In a number of cases, blood reinfusion of blood shed into the pleural cavity is used. It is permissible only if the plasma is transparent (not pink) after centrifugation, which indicates the absence of hemolysis. A positive Petrov test is an absolute contraindication to reinfusion.
Selection of surgical access
When surgical intervention is necessary, the surgeon faces a choice between open access (thoracotomy) and endoscopic access (thoracoscopy).
Modern surgery is extremely cautious regarding thoracotomy. In patients with severe chest trauma, this procedure is excessively invasive and associated with a high rate of postoperative complications. Priority is unconditionally given to minimally invasive thoracoscopy.
This method provides broad capabilities:
- Performing a thorough exploration and precisely determining the injury zone;
- Endoscopic closure of lung parenchyma defects;
- Reliable hemostasis;
- Effective removal of clotted hemothorax;
- Placement of drainage tubes under strict visual control.
To memorize the fragment displacement vector: Proximal — Anterior (P–P), Distal — Posterior.
Class and exam questions
What is the main danger of rapid blood evacuation in hemothorax?
Forced evacuation of large volumes of blood is strictly prohibited, as a sharp change in pressure increases the risk of resuming massive hemorrhage from previously damaged vessels.
Under what conditions can the chest drain for pneumothorax be removed?
The drain is removed if the lung has fully re-expanded, and air leakage through the tube has ceased and does not resume for 3–4 days.
Why is thoracoscopy preferred over thoracotomy in severe chest trauma?
Thoracotomy is associated with high invasiveness and risk of complications, which is critical for severely ill patients. Thoracoscopy allows for gentle clot removal, hemostasis, and suturing of lung defects with minimal damage.
What else to study on this topic
- Clinical diagnostics of sternal fractures
- Petrov test: methodology and interpretation
- Pathophysiology of cardiac contusion and cardiac dysfunction
- Indications for thoracotomy when thoracoscopy is not feasible
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