New Insight Regarding the Zygomaticus Minor as Related to Cosmetic Facial Injections

The present study aimed to determine the arrangement and terminal attachments of the zygomaticus minor (Zmi) muscle fibers connecting the orbital and mouth regions. The Zmi was examined in 32 specimens of embalmed Korean adult cadavers. The Zmi was present in all 32 specimens (100%). In 31 of the specimens (96.9%), the Zmi that inserted into the upper lip was formed by muscle fibers that arose from the zygomatic bone and muscle fibers that extended from the orbicularis oculi (OOc) muscle. In 14 of the specimens (43.8%), some fibers of the Zmi that arose from the zygomatic bone blended with the inferior margin of the OOc, while the other fibers inserted into the upper lip. After the Zmi fibers blended with the inferior margin of the OOc, these fibers constituted the inferior and medial margins of the OOc. These fibers were then attached to the medial palpebral ligament, the maxilla, the levator labii superioris alaeque nasi muscle, and the depressor supercilii muscle. In 30 of 32 specimens (93.8%), muscle fibers that extended from the OOc constituted the lateral margin of the Zmi, usually descending to the level between the nasal ala and the vermilion border of the upper lip and inserting into the upper lip. The obtained data will be helpful for understanding their connected movements and in kinematics and electromyographic analyses, therapies involving injections of botulinum toxin Type A, and various types of facial surgery. Clin. Anat. 31:974–980, 2018.