Revisited Anatomy of Additional Heads of Biceps Brachii Muscle and Coexisting Musculocutaneous Nerve Variants
Revisited Anatomy of Additional Heads of Biceps Brachii
Introduction:To determine the incidence and gross morphology of additional head of biceps brachii in the Indian population, and to note concurrent musculocutaneous nerve variations. Subjects and Methods: One hundred and twenty upper limbs (males- 100, females- 20) from 60 formalin-embalmed cadavers were utilized for the study.Results:The additional heads were found in 11 cadavers. Third head was present in 16.6% and fourth head in 1.7%. The variation was unilateral in 72.7% and bilateral in 27.3% cadavers. Out of 120 limbs, 14 had additional head, and 71.4% of these were left-sided. In 73.3%, additional head joined with tendon and with the belly of BB in 26.7%. Three types of origin: anterolateral, posteromedial and high humeral were observed in 60%, 26.7% and 13.3%, respectively. The additional muscle was 11.7 ± 3.9 cm in length. The mean length on the right and left sides was 9.8 ± 3.3 cm and 12.4 ± 3.9 cm, respectively. Incidence of concurrent additional head and musculocutaneous variations was 42.8%. The nerve variations were unilateral with 80% on the left, and ipsilateral to additional muscle. Conclusion: The incidence of additional head in biceps brachii is 18.3% in the Indian population. Most common presentation is of a left-sided third head, and musculocutaneous variants occur on the same side as additional muscle. Presence of extra head should be considered during the analysis of the diagnostic scans, and awareness of the associated musculocutaneous nerve variations would be helpful in avoiding complications during surgical interventions.