A Study on the Radial Nerve Supply to the Human Brachialis Muscle and Its Clinical Correlation

Fractures of the humeral shaft are commonly encountered by orthopaedic surgeons, accounting for approximately three percent of all the fractures. The appropriate treatment for such fractures requires an understanding of the anatomy of the neurovascular structures and the muscles in the arm. Aim: To study the radial nerve innervation pattern of the human brachialis muscle and its clinical correlation. Materials and Methods: In fifty upper limbs of both the sides, the brachialis muscle, the musculocutaneous nerve and the radial nerve were exposed in the arm by routine dissection. The branches to the brachialis from the radial nerve were exposed and studied in detail. The presence or absence of the muscular branches of the radial nerve to the brachialis and their number, length, site of entry into the brachialis and the distance from the lateral epicondyle to the site of emergence of these branches were studied. Results: In the present study, the radial nerve was found to supply the brachialis in 88% of the limbs and in 12% limbs, the radial nerve branches to the brachialis were absent. In 52% limbs, these branches were two in number, in 26% limbs, these were three in number and in 10% limbs, there was only one branch from the radial nerve to the brachialis. In 84% limbs, the branches entered the lower one third of the muscle, in 24% limbs, they entered the middle third of the muscle and in 4% limbs, they entered the upper third of the muscle. The average length of the muscular branches was about 4.4 cm and the average distance from the site of emergence to the lateral epicondyle was 5.63 cm. Conclusion: The clinical importance of the study of the radial nerve innervation of the brachialis muscle lies in the surgical treatment of the fractures of the shaft of the humerus by an