The muscular-deep fascial system: new findings on the anatomy of the structure attached to the superior orbital margin

Studies on the muscular-deep fascial system which connects the upper eyelid, brow, and glabella, are lacking. This study aimed to explore the fine anatomy of the muscular-deep fascial system in the region between the eyebrow and the superior orbital margin. We included eight formalin-phenol-embalmed cadavers (16 sides of specimens), and categorized them into anatomical dissections and histological sections. Five cadavers (10 sides) were dissected for gross anatomical observation, whereas all soft tissues of the other three cadavers (6 sides) were dissected for tissue sectioning and histological analysis. Three tissue blocks and 16 strips in each block were trimmed, numbered, and sliced into these specimens. Hematoxylin-Eosin and Masson's Trichrome staining were performed. In the region between the eyebrow and the superior orbital margin, the frontalis was covered by the orbicularis oculi. Fibers of the frontalis muscle penetrated into the orbicularis oculi muscle bundles, and crosslinked around the eyebrow level. Both the frontalis and the orbicularis oculi were attached to the thickened multilayered deep fascia in this region, which could be regarded as the muscular-deep fascial system. The muscular-deep fascial system connects the frontalis deep fascia and deep forehead compartments down to the orbicularis-supporting ligament. The precise anatomy of the muscular-deep fascial system in the region between the eyebrow and the superior orbital margin may provide a valuable reference for soft-tissue fixation and suspension in facial surgery.