Bilateral Variations in the Long Head of the Biceps Brachii and Coracobrachialis: Anatomical Characterization with Biomechanical and Surgical Implications

Background/Objectives: Anatomical variations in the long head of the biceps brachii tendon (LHBT) and coracobrachialis (CB) have been independently reported, but concurrent bilateral variants involving both structures are rare. Because the LHBT and CB share functional relationships around the shoulder and proximal arm and lie near the musculocutaneous nerve (MCN), combined variants may have implications for shoulder biomechanics and surgical procedures, including biceps tenodesis and the Latarjet procedure. This study describes a rare bilateral LHBT and CB variant and discusses clinical relevance. Methods: During routine cadaveric dissection of an adult female whole-body donor, bilateral variations in the LHBT and CB were identified. Morphometric measurements were obtained, including tendon length, width, circumference, origin-to-landmark distances, muscle architecture, and MCN course. The LHBT was measured from its proximal origin to the distal bicipital groove, proximal border of the pectoralis major, and musculotendinous junction bilaterally. CB morphology, number of heads, and MCN penetration pattern were documented. Results: The LHBT demonstrated bilateral elongation with atypical proximal origins and distal displacement of the musculotendinous junction. The left CB exhibited a rare three-headed configuration with superficial and bifurcated deep heads, whereas the right CB was single-headed. The MCN pierced the CB more distally on the left than typically described and demonstrated altered penetration angles. These findings increased the distance between common surgical fixation sites and adjacent neurovascular structures. Conclusions: This case represents an unusual combination of bilateral LHBT elongation and asymmetric CB morphology. Recognition of compound variants may improve surgical planning, intraoperative decision-making, and individualized rehabilitation strategies.