Sternal Fractures

Etiology

Traumatic sternal fractures are observed in approximately 8% of patients with blunt chest trauma and in about 18% of polytrauma cases involving thoracic injuries. In contrast, injuries from penetrating trauma are comparatively rare. These fractures predominantly arise from blunt, anterior chest-wall trauma and deceleration injuries, with a documented occurrence rate of 3% to 6.8% in motor vehicle collisions. Sports-related incidents, falls, and assaults contribute to the majority of remaining cases. Sternal fractures typically occur due to a direct impact on the anterior chest wall or sudden deceleration forces. The primary mechanism leading to sternal fractures is motor vehicle collisions, observed in 68% of cases, followed by falls (7.9%), motorcycle accidents (7.9%), pedestrian versus motor vehicle accidents (3.4%), and cycling accidents (1.4%). The implementation of seat belt legislation mandating shoulder restraints has contributed to an increase in the incidence of sternal fractures.[3]

Sternal insufficiency fractures frequently correlate with pronounced thoracic kyphosis resulting from multiple thoracic compression fractures, especially in advanced osteoporosis cases. The sternum and ribs are crucial components as the fourth column of structural support for the thoracic spine, and a displaced sternal fracture may indicate a significant flexion-distraction injury to the spine, thereby increasing the risk of deformity. Thoracic compression fractures caused by osteoporosis commonly lead to thoracic kyphosis, elevating the susceptibility to sternal insufficiency fractures.[4] Patients on long-term steroid therapy, postmenopausal women, and older patients are at increased risk. Stress fractures of the sternum have also been reported secondary to repetitive upper body use in such sports as weightlifting and golf.[5]

Epidemiology

The incidence of sternal fractures in motor vehicle collisions ranges from 3% to 6.8%. Paradoxically, the implementation of seat belt laws mandating shoulder restraints in modern societies has contributed to an increase in sternal fractures. Additionally, the widespread adoption of CT scanning for trauma assessment has led to increased detection of minor sternal fractures. The morbidity associated with traumatic sternal fractures typically depends more on their presentation and accompanying injuries than on the fracture itself. Isolated sternal fractures generally exhibit a lower occurrence rate of cardiorespiratory compromise and more favorable trauma assessment scores.[4]

Sternal fractures typically result from the chest striking the steering wheel, with most injuries occurring in older vehicles lacking airbag deployment. These fractures are slightly more prevalent in women than men. Sternal fractures are more common in older patients, which appears to be due to the elastic chest wall of younger patients. Younger patients are more likely to incur intrathoracic injury, as their sternum is less effective at absorbing the energy of impact.[6][7]

Pathophysiology

The majority of sternal fractures result from blunt trauma, typically occurring at the sternal manubrium or body. These fractures can be associated with significant injuries to thoracic organs, sometimes leading to fatal outcomes. Pulmonary injuries such as pneumothorax, hemothorax, pulmonary contusion, and tracheobronchial damage are common complications that often necessitate urgent care. Patients with pulmonary injuries may present with symptoms ranging from dyspnea to severe respiratory distress. Immediate resuscitation and treatment of associated injuries are critical in urgent situations.[8]

Dogrul et al identified 6 critical conditions requiring prompt investigation and intervention, including airway obstruction, tension pneumothorax, open pneumothorax, massive hemothorax, flail chest, and pericardial tamponade.[9] In cases of myocardial infarction resulting from blunt chest trauma, the causes include coronary artery dissection, acute plaque rupture, coronary artery thrombosis, cardiac contusion, and coronary artery fistula. Treatment options for myocardial infarction in these cases include coronary bypass surgery, percutaneous stenting, aspirational thrombectomy without stenting, or medical management.[10]

History and Physical

The most common causes of sternal fractures are blunt anterior chest wall trauma and deceleration injuries. Motor vehicle collisions, athletic injuries, falls, and assaults are the most frequent causes. Sternal fractures typically present with anterior chest wall pain. Up to one-fifth of cases may also experience shortness of breath. Deep breathing and coughing can exacerbate the pain. In cases of sternal stress fractures or acute insufficiency fractures, the pain may mimic other severe medical conditions due to the absence of a clear mechanism of injury, and it tends to be more diffuse.

Sternal fractures frequently involve point tenderness over the sternum. Approximately half of the reported cases may also present with soft tissue swelling, ecchymoses, or palpable deformity. Fracture-related crepitus may be noticeable upon palpation. Assessment for other associated injuries is crucial, including rib fractures, flail chest, sternoclavicular dislocation, pneumothorax, hemothorax, cardiac tamponade, myocardial contusion, pulmonary contusion, intra-abdominal injuries, spinal compression fractures, and other traumatic injuries.[11]

Evaluation

Chest radiographs are usually the initial imaging modality used for patients suspected of having a sternal injury. The anteroposterior radiograph has a sensitivity of only 50% for detecting sternal fractures. A lateral radiographic view increases sensitivity and is usually diagnostic, as most sternal fractures are transverse, with any displacement occurring in the sagittal plane.[2][12] 

A chest CT scan is another standard diagnostic test for patients with a high index of suspicion of sternal fracture. Axial CT scans may be less sensitive than plain radiographs, as they can sometimes miss transverse sternal fractures. Spiral CT scans are likely the most sensitive, although no gold standard exists. Chest CT scans are also advantageous in ruling out associated injuries due to sternal fractures. Ultrasonography can detect sternal fractures with equal or greater sensitivity than plain radiography. Bedside ultrasonography may significantly reduce the time to diagnosis; however, limiting factors, including inter-operator variability, must be considered.

Cardiac monitoring and pulse oximetry should be initiated for all patients in the emergency department with sternal fractures. Electrocardiograms should be conducted to assess signs of myocardial contusions, such as arrhythmias, conduction disturbances, sinus tachycardia, or ST-segment changes. Enzyme markers of cardiac injury may be helpful if cardiac contusion is suspected, with troponin elevation particularly indicative of myocardial injury. Echocardiography assists in detecting myocardial contusions by providing a direct view of wall motion abnormalities.

Treatment / Management

Clinicians should adhere to the Advanced Trauma Life Support (ATLS) guidelines when managing acute sternal fractures. Following the evaluation of airway, breathing, and circulation, a primary survey should be conducted to identify and treat any life-threatening conditions. In addition, any associated injuries, such as tension pneumothorax, hemothorax, cardiac tamponade, and flail chest, should be identified and treated. Upon stabilization, a secondary survey should be conducted. This stage involves managing associated chest injuries such as rib fractures, pulmonary contusions, and blunt myocardial injury, which are commonly associated with sternal fractures and can be addressed effectively at this stage.[13][14] (B3)

Surgical treatment may be appropriate in certain cases. Less frequently encountered injury patterns include blunt trauma to the tracheobronchial tree, esophagus, diaphragm, heart, or aorta, which often require operative intervention. These types of injuries usually necessitate operative intervention.[15] Electrocardiography and cardiac monitoring are essential for patients with sternal fractures. Those showing signs of myocardial contusion should be admitted for further evaluation and management. Patients with associated intrathoracic injuries, hemodynamic instability, or uncontrolled pain should also be admitted for observation. Older patients warrant close monitoring due to a heightened risk of respiratory complications.

Adequate analgesia is the mainstay of treatment for isolated sternal fractures. Hospital admission is unnecessary if no concerns are identified during clinical evaluation. Patients should follow up with their primary care physician within the first 24 hours. Deep breathing exercises are beneficial in preventing pulmonary complications. Surgical fixation may be required for significantly displaced or unstable fractures. However, most isolated sternal fractures heal spontaneously over an average period of 10 weeks.

Differential Diagnosis

The differential diagnoses of an acute sternal injury are broad and include rib fractures, flail chest, sternoclavicular dislocation, pneumothorax, hemothorax, cardiac tamponade, myocardial contusion, pulmonary contusion, intra-abdominal injuries, spinal compression fractures, and other traumatic injuries that must be considered and ruled out.

Prognosis

The mortality rate for patients with sternal fractures admitted to the hospital is low, at 8% within 30 days post-injury. This aligns with other evidence indicating that despite the severity of the injury, mortality remains low.[11] Isolated sternal fractures have an excellent prognosis, with an overall mortality rate of 0.7%. Most patients with these solitary injuries recover fully within the average reported period of 10 weeks. Surgical fixation may be required in rare cases of chronic sternal pain or nonunion. Up to two-thirds of sternal fractures involve associated injuries, with mortality rates ranging from 25% to 45% in these cases.

Complications

Complications from sternal fractures often stem from associated injuries. Displaced or unstable sternal fractures increase the risk of pulmonary injuries, pericardial effusions, rib fractures, and spinal compression fractures. Chest pain can persist for 8 to 12 weeks post-injury. Painful inspiration may lead to atelectasis, pneumonia, and other pulmonary complications. The nonunion, false joint formation and overlap deformities of sternal fractures are rare but may necessitate delayed surgical intervention. Advanced age, osteoporosis, prolonged steroid use, and diabetes elevate the risk of delayed healing. Rare complications such as osteomyelitis, sternal abscess, and mediastinitis may occur. Large hematoma formation, intravenous drug abuse, and concurrent staphylococcal infections increase the risk of infectious complications.