Bilateral quadricipital biceps brachii: a rare anatomical variation with clinical implications.

We report our observation of bilateral quadricipital biceps brachii muscle with usual coracoid and glenoid heads and two supernumerary heads arising from the anterior surface of the humerus above the origin of the brachialis muscle. On each side, the lateral supernumerary head merged with the fleshy part of the long head, and the medial heads inserted into the biceps tendon and partially contributed to the bicipital aponeurosis. The median nerve and brachial artery coursed medial to these supernumerary heads, which posed no perceivable risk of neurovascular compression. This variation highlights the complexity and clinical relevance of upper limb muscular anatomy. The occurrence of a four- or five-headed biceps brachii remains exceedingly rare. This paper includes a review of similar cases previously reported in the literature.