Quantified relationships of the radial nerve with the radial groove and selected humeral landmarks

Anatomical relationships between the radial nerve, the deltoid muscle insertions and several bony landmarks have been investigated to assess the feasibility of surgical transfer of the deltoid transfer during humeral osteotomy. Eleven embalmed human specimens were dissected. Each specimen included the whole thorax, both shoulders and upper limbs. Spatial position of the radial nerve along the radial groove, the deltoid muscle, and several anatomical landmarks was digitised using a three-dimensional (3D) digitiser. Sixteen distances and one angle characterizing the relationships between the path of the radial nerve and the landmarks were processed. Results showed that the average distance between the emergence of the radial nerve from the lateral intermuscular septum and the most distal insertion point of the deltoid muscle on the humeral bone shaft was 47.6 ± 18.5 mm. The angle between a line extending from the entry of the radial nerve into the radial sulcus and its point of emergence (REN–REM line), and on the other hand a line running from the radial emergence and the deltoid muscle tip (REM–DELTIP line) was in average 23.5 ± 6.7°. The length of four lines running perpendicular to REM–DELTIP and crossing each quarter of the REN–REM line were interpolated. The length of these four lines was, from proximal to distal, 31.3 ± 11.5 mm; 23.0 ± 7.8 mm; 16.5 ± 6.2 mm; and 7.6 ± 2.6 mm, respectively. These results described in a quantitative way the path of the radial nerve in respect to the humeral bone and the deltoid muscle. These data will be used for further development of a humeral osteotomy protocol taking into account the spatial position of the radial nerve to orientate safely the surgical tools used to cut the humeral shaft.