Figure 3 : Landmarks for an upper partial median sternotomy. The
incision is carried through the midline of the sternum generally to the
2nd intercostal space. Critical for exposure is an
adequate extension of the neck with a good size shoulder roll,
especially in infants.
A total thymectomy is then performed taking care not to injure the
phrenic nerves bilaterally. This is critical as the thymus is often
large and acts as a space occupying lesion. It is preferable not to
enter the pleural spaces. The innominate vein is then mobilized and
retracted superiorly. The innominate artery is then dissected only on
its anterior aspect and the pericardial reflection at its base on the
aortic arch is opened in a limited fashion. Again, it is critical not to
circumferentially dissect the innominate artery as this will lead to a
loss of the natural adhesion between it and the anterior surface of the
trachea. A pretracheal plane is thus not developed. This is
important. As the innominate artery is pulled anteriorly towards the
sternum (given the space after the thymectomy), besides relieving the
tracheal compression, it helps support the associated tracheomalacia by
suspending the anterior wall of the trachea indirectly to the sternum
(Figure 4 ).