Anatomic considerations regarding the posterior interosseous nerve at the elbow

The relationship of the posterior interosseous nerve (PIN) to the radius was studied to determine the change in position associated with forearm motion because of the risk of injury during surgical exposure of the lateral elbow. The distance from the PIN to the radiocapitellar joint (RCJ) was measured in 24 cadaveric specimens in pronation, neutral rotation, and supination. The mean distance from the PIN to the RCJ was 4.6 +/- 0.5 cm, 5.3 +/- 0.6 cm, and 5.7 +/- 0.7 cm in supination, neutral rotation, and pronation, respectively. In pronation, there was substantial variation of this distance, with a minimum distance of 4.3 cm. In supination, the minimum distance was 4.0 cm. On the basis of limited PIN distal translation, noted with pronation, as well as the variation between individuals, we recommend limiting dissection to 4.0 cm from the RCJ during a lateral approach without formal identification of the PIN. This safe zone is recommended regardless of forearm rotation, in contrast to the recommendation of prior authors, as pronation does not reliably increase the distance of the PIN to the RCJ.