Anatomical considerations regarding the posterior interosseous nerve during posterolateral approaches to the proximal part of the radius

Background: The purpose of our study was to quantify the dimensions of a su rgically safe zone along the proximal part of the radius, from the posterol ateral aspect. Methods: The posterolateral approach between the anconeus and the extensor carpi ulnaris was performed in thirty-two cadaveric specimens, and the post erior interosseous nerve was exposed. Forearms were measured from the radia l styloid process to the radio-capitellar joint. The distance from the capi tellum to the point where the posterior interosseous nerve crossed the radi al shaft and the angle between the nerve and the shaft were measured with f orearms in pronation and supination. Results: Pronation of the forearm allowed safe exposure of at least the pro ximal thirty-eight millimeters of the lateral aspect of the radius, with an average proximal safe zone of 52.0 +/- 7.8 millimeters, Supination decreas ed this proximal safe zone to as little as twenty-two millimeters and an av erage of 33.4 +/- 5.7 millimeters. The angle formed by the posterior intero sseous nerve and the radial shaft in supination averaged 47.4 +/- 6.8 degre es; this decreased to 27.8 +/- 6.7 degrees with pronation. Conclusions: Approaching the lateral aspect of the proximal part of the rad ius is safest in pronation.