Posterior junction line

The posterior junction (or junctional) line is formed by the apposition of the pleural surfaces of the posteromedial surfaces of the upper lobes of the lungs, posteriorly to the esophagus but anterior to the thoracic spine (usually T3-T5) .

There are many causes for an abnormal appearance of this line :

• posterior mediastinum masses
  • esophageal malignancy
  • lymphadenopathy (from a variety of causes)
  • neurogenic disease
  • aortic disease
• retrosternal goiter
• hyperinflation or collapse of one lung can cause lateral displacement

Radiographic features

Plain radiograph

• seen in ~30% of PA chest x-rays
• normally appears as a thin, vertical line projecting through the trachea that extends to the pleural dome above the clavicles to the level of the aortic arch
• extends more superiorly than the anterior junction line