“Zone of Vulnerability” for Radial Nerve Injury: Anatomic Study

The authors of this study sought improved understanding of the radial nerve course through the brachium and hypothesized that the most proximal aspect of the triceps tendon (PATT) serves as a useful superficial landmark for localizing the nerve. It was also hypothesized that a poorly appreciated area of vulnerability for nerve injury exists where the radial nerve runs along the lateral cortex of the humerus proximal to its transit through the lateral intermuscular septum (LIMS). The authors assessed 33 fresh-frozen cadaveric specimens. A 6.7-cm span of the nerve lies directly on the periosteum of the humerus before piercing the LIMS. The proximal 4.6 cm abuts the posterior cortex. The final 2.1 cm just proximal to the LIMS runs along the lateral cortex. The nerve at the posterior midline of the humerus is 2.3 cm proximal to the level of the PATT. The radial nerve lies directly on the lateral humeral cortex for 2 cm proximal to its transit through the LIMS. The PATT appears to be a consistent and practical superficial landmark to determine the location of the radial nerve from a posterior approach. Key words: anatomy, iatrogenic injury, radial nerve, triceps tendon, zone of vulnerability