Anomalous three-headed biceps brachii with attachment to the medial epicondyle.

The biceps brachii (BB) demonstrates considerable anatomical variability, with supernumerary heads among the most frequently reported variations. Although accessory heads typically insert onto the common BB tendon, alternative insertion patterns may have important clinical implications, particularly when they alter the relationship of the muscle to adjacent neurovascular structures. During routine dissection of an 82-year-old male cadaver, a three-headed BB was identified in the right upper limb. A prominent third head originated from muscle fibers of the primary BB in the distal third of the humerus and inserted onto both the radial tuberosity and the bicipital aponeurosis. In contrast, the primary BB, formed by the convergence of the long and short heads, exhibited an anomalous insertion onto the medial epicondyle of the humerus. This previously undocumented insertional pattern was positioned directly superficial to the brachial artery and median nerve. The aberrant tendon measured 7.2 cm in length, and the third head measured 9.7 × 2.4 cm. The variation was unilateral, and no abnormalities were observed in the origins of the long or short heads. Supernumerary heads of the BB are well described. However, insertion of the primary BB onto the medial epicondyle has not been previously reported. Given its proximity to the median nerve and brachial artery, this variant may have resulted in neurovascular compression during life. Recognition of these rare variants is critical for accurate clinical assessment, interpretation of imaging, and planning of surgical interventions.