A magnetic resonance imaging analysis of the infraclavicular region: can brachial plexus depth be estimated before needle insertion?

In this study we examined the anatomy of the infraclavicular region to assess the possibility of estimating brachial plexus depth before performing an infraclavicular block, by using readily identifiable landmarks such as the coracoid process (CP) and the clavicle (CL). Four parasagittal planes across the infraclavicular region were analyzed in 21 individual series of magnetic resonance imaging studies. Measurements included distance to the plexus from the skin of the anterior chest wall, position of the plexus relative to the CL, and clavicular width. The brachial plexus is located directly below the CL in the parasagittal plane 1 cm medial to the CP. If one inserts a needle in this same plane at a point in line with the inferomedial edge of the CP, then plexus depth can be estimated as follows. If the needle is raised, as a whole, straight up from the planned point of insertion to be level with the top of the CL, then the distance from the tip of the needle to a point midway across the width of the CL is equivalent to the distance from the insertion point to the plexus. Furthermore, not only is it uncommon to find the lung in this same parasagittal plane, but when it does appear, it is well behind the plexus. Estimating plexus depth, or "depth gauging," in the infraclavicular region is achievable and is a potentially useful strategy. Further study is required to confirm this finding in the clinical environment.