Platysma and the cervical superficial musculoaponeurotic system — Comparative analysis of facial crease and platysmal band development

The superficial musculoaponeurotic system connects the mimic muscles to the skin, allowing mimic expressions with regional morphological architectural differences. The aim of this study was to perform an architectural analysis of the cervical platysma-skin interaction, determine the morphological implications in platysmal band development and compare the findings to the facial SMAS architectural types.Full-thickness blocks of skin, SMAS and platysma from seven hemifaces (three male and two female) and full-thickness blocks of skin, SMAS and mimic muscles of the periorbital, perioral, forehead and midfacial regions from six hemifaces (three male and three female) of donor bodies were collected postmortem. Serial histological sections were cut and stained with Azan. After the morphological analysis, three-dimensional reconstruction of the tissue block was performed with AutoCAD. The morphological and mechanical properties of the different facial SMAS types were compared with those of the cervical SMAS.The architecture of the cervical SMAS (type V) consists of parallel, aligned septum fibrosus profundus and septum fibrosus superficialis tissue connected by vertical, aligned septa fibrotica commisurales tissue delimiting fatty tissue compartments transferring platysmal contractions to the skin. The facial morphological dynamic mimic pattern (SMAS types I, II and III) describes the point-by-point transfer of mimic muscle bundle contractions to the skin, explaining facial crease formation. The cervical morphological dynamic mimic pattern (SMAS type V) can be explained by dual traction force collimation over the septum fibrosus superficialis and profundus in platysmal band development.The cervical SMAS (type V) description supports the hypothesis that the SMAS and platysma have different morphological origins. The two different facial and cervical morphological dynamic mimic patterns support the phenotypical difference between facial fold and platysmal band development.