A Case of Third Head of Biceps Brachii along with an Additional Slip of Insertion
Muscular variations in the upper extremity are uncommon. Biceps brachii (BB) is a muscle of anterior compartment of the arm, with two heads of origin and it inserts into the radial tuberosity and antebrachial fascia through a tendon and aponeurosis respectively. During routine dissection for undergraduate medical students, we encountered an unusual case of third head and additional slip of insertion of BB in the upper limb of an approximately 60-year-old male cadaver. The third head of the BB was arising from the lower 1/3rd of the anterolateral surface of the humerus along with the fibers of brachialis. The median nerve was passing through this third head as it entered into the cubital fossa.The fibres of the third head formeda separate tendon which distally expanded to form bicipital aponeurosis and blended with antebrachial fascia. Some of the lateral fibers of the long head of BB got split from the main belly in the middle 1/3rd of the arm and was inserted to the shaft of the humerus. The median nerve may get compressed as it passes through the third head of BB and can cause weakness of flexor muscles of forearm and hand. Thus, it is crucial that clinicians must know aboutsuch variations to treat the compression neuropathies in the arm and forearm. Similarly, slip of muscle fibers of BB which are ending in the arm instead of forearm may restrict the movements of the shoulder joint for a limited extent.
Keywords - Biceps Brachii, Brachialis, Median Nerve, Neuropathies