Anatomical study of the third head of biceps brachii muscle and its innervation by median nerve in human dissection

Abstract

Several studies have described the biceps brachii muscle as one of the muscles in the upper limb with most frequent anatomical variations. They also reported the presence of this anomaly in varying frequency in different populations. The aim of this study was to assess the anatomical description of the third head of biceps brachii muscle and its abnormal innervation in human autopsies which would be of value for the surgical approach in the arm. Forty arms (20 cadavers) were dissected. The upper arm and axilla region of all cadavers were dissected carefully, then the biceps brachii muscle and surrounding structures were clearly demonstrated to show any muscle variations and abnormalities of its nerve supply, then different photographs were collected. The present study demonstrated the third head of the biceps brachii muscle in 6 out of 40 specimens (15%). The third head of biceps brachii was dominant in the right arm (4 specimens) in contrast to two specimens in the left arms and the muscle was innervated by the median nerve instead of normal innervations by the musculocutaneous nerve. In conclusion, the present study of anatomical variations of the biceps brachii muscle in the arm may contribute to a better developmental understanding and surgical approach.   Key words: Biceps brachii, anatomical variation, median and musculocutaneous nerves, human autopsy.