Background: Iatrogenic radial nerve injury following posterior approach of the humerus has been reported from 3 to 11%.
The surgeon's awareness of nerve location may lower this complication.

Objective: The objective of this study was to evaluate a system to preoperatively determine the location of the radial nerve using superficial osseous landmarks to help avoid radial nerve injury,
a potential complication in fixation of a fracture of the humerus.

Materials and Methods: Twenty-six fresh frozen upper extremities from adult cadavers were dissected and the distances from the radial nerve at the midhumeral axis to the medial epicondyle, to the lateral epicondyle and to the ulnar border of the olecranon were measured and the correlation with the transepicondylar width [TW] was calculated.

Results: The radial nerve was located an average of 2.33 times the TW from the medial epicondyle, 2.27 times the TW from the lateral epicondyle and 2.74 times the TW from ulnar border of olecranon.
The correlation between those distances and the radial nerve was found to be statistically significant.

Conclusion: The transepicondylar width is an easily accessed bony reference which can be used to calculate the location of the radial nerve in the posterior MIPO approach, allowing the surgeon to protect the nerve by limiting exposure at the point predicted by the transepicondylar width.

Keywords: Radial nerve, Posterior approach to humerus, Distal humeral shaft fracture