The mediastinal structures said to lie on a horizontal plane at the le
vel of the manubriosternal joint (manubriosternal plane) in the cadave
r include the bifurcation of the trachea, the concavity of the arch of
the aorta, and the azygos Vein as it arches over the right principal
bronchus to enter the superior vena cava. We have reviewed CT scans of
the thorax in 51 subjects to determine 1) whether these structures li
e consistently at this level in the living thorax and 2) the vertebral
revel of this plane. We found that the bifurcation of the trachea lay
at the plane in 41% of subjects, that the plane passed through the co
ncavity of the arch of the aorta in 49% of subjects, and that, althoug
h there was notable individual variation, the manubriosternal plane pa
ssed through the upper part of the fifth thoracic vertebra in 53% of c
ases. (C) 1997 Wiley-Liss, Inc.