Supernumerary head of biceps brachii and branching pattern of the musculocutaneus nerve in Japanese

Abstract

Out of 546 upper limbs (273 cadavers), supernumerary heads of the biceps brachii were found in 75 limbs (13.7%) of 58 cadavers (21.3%). The form, origin, and insertion of the supernumerary heads, and branching pattern of the musculocutaneus nerve were studied. In addition, the dimensions of the heads were measured. In many cases, the supernumerary head arose from the humerus, between the insertion of the coracobrachialis and the upper part of the origin of the brachialis, and/or from the medial intermuscular septum. In a few cases, a supernumerary head arose from the tendon of the pectoralis major or the deltoid, or from the articular capsule, or from the crest of the greater tubercle. The supernumerary heads typically joined the common belly, or the aponeurosis of the biceps brachii. Some heads joined the belly of the long head or that of the short head. In the examination of the branching pattern of the musculocutaneus nerve, communication between the musculocutaneus nerve and the median nerve was found in 43 out of the 75 limbs (57.3%). The communicating branch ran from the musculocutaneus nerve to the median nerve in 24, from the median nerve to the musculocutaneus nerve in 12, in both directions in 5, or in another type of pattern in 2 out of 43 limbs. Sometimes a branch of the musculocutaneus nerve ran around a supernumerary head and then fused with the present trunk. The presence of a supernumerary head seemed to affect the course and branching of the musculocutaneus nerve.

Morphology and clinical implication of the extra-head of biceps brachii muscle

“…The later authors added that the commonest site of origin of that extra head of the biceps was the medial aspect of the humerus in common with the insertion of the coracobrachialis muscle, while the least one was a fascial origin from the medial side of deltoid muscle and the lateral side of the short head of biceps muscle. In disagreement with the present study, the third head of the biceps muscle was formed of a group of fascicles that arose from the coracoid process of scapula, the pectoralis major tendon or from the anterior aspect of humerus just below the lesser tubercle crest [21], head of humerus, the articular capsule of shoulder joint [18] or from the shaft of humerus itself [7,8].…”

“…The incidence of occurrence of these variations is 37.5% in Colombians [18], 21.5% in South Africans blacks, 8.3% among South African whites [3], 18% in Japanese [7], 15% in Turkish [16], 7.1% in Indians [17].…”

Communication between musculocutaneous and median nerves: a case report

“…17 In diagnostic clinical neurophysiology, variations in connections between musculocutaneous nerve and median nerve may have significance. These variations have clinical importance in post-traumatic evaluations and exploratory interventions of the arm for peripheral repair.…”

A Cadaveric Study of Accessory Heads of Biceps Brachii in South Indian Population

“…The accessory head presents as a group of accessory muscle fascicles which may originate from bones like coracoid process, proximal head of the humerus or may arise from the tendon of Pectoralis major or articular capsule of the humerus [7]. Kosugi et al observed that the supernumerary head of biceps arose from the humerus between the insertion of coracobrachialis and upper part of origin of brachialis, from medial intermuscular septum, from the tendon of the pectoralis major, the deltoid tuberosity, the articular capsule, or the crest of the greater tubercle [8].…”