An anatomical study of muscular branches of radial nerve in the forearm / 中华骨科杂志

ABSTRACT

Objective To observe the anatomical features of muscular branches of radial nerve in the forearm. Methods Forty seven adult embalmed cadaver arms were dissected under 4? loupe magnification. The radial nerve was identified in the interval between the brachioradialis and brachialis at the upper arm 10 cm proximal to the lateral humeral epicondyle (LHE). The nerve and branches were dissected and observed. The number of branches entering the muscles was counted and the following measurements were performed along the radial nerve and branches with a vernier caliper (accurate to 0.1 mm) distances from the origin point and muscle entry point of each branch to the LHE, the distance between the LHE and the styloid process of ulna (SPU). Data were pooled among all specimens (n=47) to calculate mean and standard deviation. Results In 35 of 47 (74.5%) specimens, the deep branch of the radial nerve coursed along the line between the LHE and the SPU. In all specimens, extensor indicis was the last muscle to be innervated. The average distance from the LHE to the origin point of extensor indicis branch was (160.6?12.1) mm, and that from the LHE to the SPU was (231.7?14.6) mm. The average proportionality between these two distances was 0.7?0.1. There was a large variation in branch number. The muscle with the highest branch number (4.6 averaged) was the extensor digitorum communis and that with the lowest number (1.1 averaged) were extensor policis longus and extensor indicis proprius. In 29 of 47 (61.7%), extensor carpi radialis brevis (ECRB) branch originated from the superficial branch of the radial nerve. In 15 of 47 (31.9%), the branch came from the deep branch of the radial nerve. In 3 of 47 (6.4%), the branch emanated from the radial nerve as 1 branch of a trifurcation (with the other branches being the deep branch and the superficial branch of the radial nerve). Conclusion With the forearm being pronated, the proximal 7/10 of the line between the LHE and the SPU can be considered as the projection on body surface of the deep branch of the radial nerve. The deep branch of the radial nerve may be damaged by operators improper dragging and detaching in surgery with the following reasons branch lengths of extensor digitorum, extensor carpi ulnaris and extensor digiti minimi are short relatively, and origin points of these branches are more close than others to the point through which the deep branch of the radial nerve come out supinator. Differences in muscle architecture and function may be the reason that there is such variation in branch number. Discrepancies between studies about the ECRB branch origin may be related with the fault committed by researchers in dissecting.