In vivo cross-sectional topographic anatomy at sternal angle on magnetic resonance imaging

Abstract

Introduction: The manubriosternal angle, first described by Louis in 1825, is an important landmark in the anatomy of the thorax and has been conventionally described as corresponding to the T4–5 IV disc level based on cadaveric dissections. The objective of this study was to document the level of the angle of Louis and various anatomic structures that also correspond to the same level in living individuals based on multiplanar magnetic resonance (MR) images. Material and Methods: We reviewed MR scans of the cervicodorsal spine of 262 individuals comprising 174 males and 88 females in the age range 14–76 years. For each individual, the vertebral level of the following structures was noted on T1-weighted (T1W)/T2-weighted (T2W) turbo spin echo (TSE) coronal and sagittal images, namely tracheal bifurcation (TB), aortic arch (AA), and sternal angle (SA). Results: The SA was most commonly seen corresponding to the T5 vertebral body level (45.20%) and at T4–5 IV disc level in only 20.45% of the individuals. The convexity of the arch of the aorta was seen in the majority of the individuals corresponding to the T3 vertebral body level (47.96%). TB was seen at T4 level in 34.35% and only in 22.69% at the T4–5 IV disc level. Discussion and Conclusion: The anatomical level of the SA, AA, and TB in living individuals as assessed on MR images is significantly different from the traditionally held belief based on cadaveric dissections.