An anatomical insight into the third head of biceps brachii muscle.

BACKGROUND: The biceps brachii muscle is known to show variations in the number of heads. This study was performed to evaluate the variations in the origin of the biceps brachii muscle heads. MATERIALS AND METHODS: Both extremities of 48 formalin fixed cadavers (n = 96) were studied for abnormal heads of biceps brachii muscle. The flexor compartment of the arm was dissected and the attachments of the biceps brachii muscle were studied in detail. Appropriate photographs were taken. RESULTS: Among ninety six upper limbs studied, we observed three heads of biceps on both sides of a male cadaver aged 56 yrs (3.33%). The two heads of the biceps arose from its usual position but the anomalous third head arose from the anterior limb of the 'V' shaped insertion of the deltoid muscle on the humerus. The third head was found to fuse with the common belly of the muscle well before the bicipital tendon and its aponeurosis. Bilaterally this third head was supplied by a twig of the musculocutaneous nerve. No other abnormalities relating to the biceps were observed in any of the sides of the other 47 cadavers (n = 94). CONCLUSION: Our study revealed that the incidence of third head of biceps brachii may be approximately 3.33 % but larger studies are needed to confirm this fact. The third head of biceps brachii may be an incidental finding at autopsy or during routine anatomical dissections. Unless symptomatic, the third head of biceps brachii may not be detected in clinical studies (Fig. 3, Ref. 15).