Straight back syndrome

Last revised by Daniel J Bell on 16 Dec 2018

Straight back syndrome refers to decreased thoracic kyphosis ("flattening") and decreased anteroposterior thoracic diameter, such that there is compression of cardiovascular or bronchial structures. 

It should not be confused with flat back syndrome, which refers to decreased lumbar lordosis, often in the setting of spinal fusion and without intrathoracic compression 3.

Clinical presentation

Most patients are asymptomatic. On precordial auscultation, individuals with this condition can have an ejection systolic murmur over the pulmonary area due to compression of the right ventricular outflow tract (RVOT) 2. Uncommonly, patients may complain of chest pain, palpitations and lightheadedness.

More rarely, patients may present with dyspnea, resulting from compression of the trachea or bronchi 6.

Radiographic features

Plain radiograph
  • loss of the normal kyphosis of the upper thoracic spine 2,4,5
  • the distance from the middle of the anterior border of the T8 vertebra to a vertical line connecting the anterior borders of T4 and T12 is <1.2 cm 2,4
  • the anteroposterior diameter on the lateral chest x-ray from anterior border of the T8 vertebra to the posterior border of the sternum is <10-11 cm 3
  • the cardiothoracic ratio is usually less than 0.5
  • the heart may be shifted leftwards with a prominence the main pulmonary artery 5

There is an association with mitral valve prolapse

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Cases and figures

  • Case 1
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