Identification of most consistent and reliable anatomical landmark to locate and protect radial nerve during posterior approach to humerus: a cadaveric study

The location of the radial nerve (RN) is described with various bony landmarks, but such may be disturbed in the setting of fracture and dislocation of bone. Alternative soft tissue landmarks would be helpful to locate the nerve in such setting. To recognize certain anatomic landmarks to identify, locate and protect RN from any iatrogenic injury during surgical intervention such as open reduction and internal fixation. Forty arms belonging to 20 adult cadavers were used for this study. We measured the distance of RN from the point of confluence of triceps aponeurosis (TA), tip of the acromion and tip of the lateral epicondyle along the long axis of the humerus. These distances were correlated with the upper arm length (UAL). The average UAL was 32.64 +/- 0.64 cm. The distance of the RN from the point of confluence of TA (tricepso-radial distance, TRD), tip of acromion (acromion-radial distance) and tip of lateral epicondyle of humerus (condylo-radial distance, CRD) was 3.59 +/- 0.16 cm, 14.27 +/- 0.59 cm, and 17.14 +/- 1.29 cm respectively. No correlation was found with UAL. Statistically, TRD showed the least variability and CRD showed maximum variability. The minimum TRD was found to be 3.00 cm. So this should be considered as the maximum permissible length of the triceps split. The point of confluence of the TA appears to be the most stable and reliable anatomic landmark for localization of the RN during the posterior approach to the humerus.