A new method of predicting radial nerve location: a cadaveric study

This study aimed to present a new method to predict an area with no Radial Nerve (RN) distribution (safe zone of the RN) in the middle and lower of the upper limb. The RN(60 in total) were dissected from 30 adult cadavers (20 males and 10 females). Acromial Angle, Olecranon, and Lateral Epicondyle of Humerus were selected as reference points. The linear projection of the RN on Acromial Angle-Olecranon and Acromial Angle-Lateral Epicondyle of Humerus were marked as 'Intersection Point A' and 'Intersection Point B'. The lengths of Acromial Angle-Lateral Epicondyle of Humerus, Acromial Angle-Olecranon, Intersection Point A-Olecranon, Intersection Point B-Lateral Epicondyle of Humerus were measured. In this connection, the safe zone of the RN on the middle and lower Humerus was illustrated using Python3.11 and PyCharm2023.3.4. The mean position of Intersection Point A was located at (59.9 +/- 6.2)% of the total length of Acromial Angle-Olecranon distally and the mean position of Intersection Point B was at (42.9 +/- 6.6)% of the Acromial Angle-Lateral Epicondyle of Humerus. We identified absolute safe zone (with no RN distribution) on the middle and lower part of the Humerus enclosed by Olecranon, Lateral Epicondyle of Humerus, the 42.50% point of Acromial Angle-Olecranon distally, and the 28.10% point of Acromial Angle-Lateral Epicondyle of Humerus distally. In addition, relative safe zone (with less than 5% probability of the RN distribution) enclosed by Olecranon, Lateral Epicondyle of Humerus, the 50.33% point of Acromial Angle-Olecranon distally, the 32.98% point of Acromial Angle-Lateral Epicondyle of Humerus distally. Data in this study can help us locate the RN with body surface markers during Humerus fracture fixation.