Clinical implications of additional heads of biceps brachii muscle

ABSTRACT

Biceps brachii is a superficial muscle of the flexor compartment of arm. It is a strong flexor and a supinator of forearm. It is one of the most variable muscles in terms of number of its heads of origin, so the present study proposes to dissect North Indian cadavers to see the frequency of occurrence of more than two heads of biceps brachii and discusses its clinical implications. To determine the prevalence of accessory heads of biceps brachii, their inervation and any anomalous course of neurovascular bundle in the front of arm. Number of heads of biceps brachii muscle were studied in 77 adult human cacdavers [n-154]. Presence of additional heads of biceps brachii and any variation in the course of neurovascular bundle in the front of arm were noted. It was observed that the left upper limb of only one middle aged male cadaver had four heads of origin of biceps brachii i.e. the long head from supraglenoid tubercle of scapula, short head from tip of coracoid process of scapula and the two accessory heads from the anteromedial surface of the humerus between the insertion of coracobrachialis and the origin of brachialis. The musculocutaneous nerve took origin from the lateral cord normally and pierced through coracobrachialis to enter the flexor compartment of forearm. Then it passed between the two accessory heads before supplying brachialis and continued as lateral cutaneous nerve of forearm. Each head of biceps brachii was individually innervated by fibers from musculocutaneous nerve. No other anomalies in the neurovascular bundle were observed. Awareness of the different course of musculocutaneous nerve and origin of supernumerary heads of biceps brachii is of importance to academicians, surgeons, traumatologists, orthopaedicians and plastic