Associate Professor Oregon Health and Science University Portland, Oregon, United States
Abstract Body : Biceps brachii is a functionally important muscle of the anterior compartment of the arm, which is typically innervated by the musculocutaneous nerve. The biceps muscle is typically composed of two heads. These include: the long head, which originates from the supraglenoid tubercle, and the short head, which originates from the tip of the coracoid process. The fused long and short heads of the biceps insert into the radial tuberosity and fascia of forearm via the bicipital aponeurosis. Variations may be present in the form of additional heads of origin or they may be present at its insertion. These variations may affect action of muscle and may cause compression of nearby neurovascular structures. Familiarity with the prevalence of anatomical variations of the biceps brachii in specific populations and awareness of the presence of unexpected origins or insertions prior to surgery can help improve surgical approaches and outcomes. Further study into the functional implications of common variations can also provide insights into injury risks and rehabilitation considerations.
During a routine cadaveric dissection of a 93-year-old male at Oregon Health and Science University., we observed an accessory head of the biceps brachii muscle originating from the ventral mid-shaft of the humerus near the insertion of the coracobrachialis and origin of the brachialis muscle. The accessory head inserted into the deep surface of the biceps brachii at the point of fusion of the long and short heads. We also noted muscle slips from both the distal coracobrachialis and proximal brachialis contributing to the functional origin of the accessory biceps head, as well as muscle fibers of the accessory head inserting into the medial intermuscular septum of the arm near the distal attachment to the fused biceps brachii belly. The accessory head of the biceps brachii muscle, as well as the inferior brachialis muscle were noted to be innervated by fibers from the median nerve as it passed though the medial part of the anterior compartment of the arm.
