Atypical Origin of the Pectoral Nerves: Morphological Insights for Orthopedic, Reconstructive, and Trauma Surgeons

Anatomical variations in the brachial plexus can significantly affect upper-extremity surgical procedures. This report highlights a rare case where both pectoralis muscles receive accessory innervation. The pectoralis major exhibited three additional branches stemming directly from the anterior divisions of the superior and middle trunks, effectively bypassing the lateral cord. The pectoralis minor likewise demonstrated variant innervation, receiving two additional branches. One was an unexpected confluence in which a branch destined for the pectoralis major coursed through and innervated the pectoralis minor, despite the pectoralis minor typically receiving its own independent branch. The other branch originated from the anterior division of the middle trunk. Furthermore, a variant ansa pectoralis was identified, originating from the anterior division of the middle trunk and medial cord, and giving rise to the medial and lateral pectoral nerves. This unique configuration may present clinical implications for surgeons, particularly during procedures involving the proximal upper limb and supraclavicular pectoral region. Identifying these variations can help minimize the risk of iatrogenic nerve injury and enhance surgical planning.