Morphological analysis and three-dimensional reconstruction of the SMAS surrounding the nasolabial fold

The superficial musculoaponeurotic system (SMAS), a structure that has been discussed with some controversy, has a complex morphological architecture.

Histological analysis was performed on tissue blocks of the nasolabial fold (NLF) collected postmortem from formalin-fixed bodies of one male and one female donor. Serial histological sections were made, stained and digitized. Three-dimensional reconstructions of the histological structures were performed. Specimen- and location-specific differences were determined. SEM analysis of the NLF tissue block was performed.

The NLF SMAS is a fibro-muscular, three-dimensional meshwork bolstered with fat cells. Two SMAS structure types were identified adjacent to the NLF. The cheek SMAS structure showed a regular, vertical and parallel alignment of the fibrous septa, building a three-dimensional meshwork of intercommunicating compartments. It changed its morphology, condensing while transiting the NLF and passing over to form an irregular structure in the upper lip region. SEM analysis demonstrated the connection between the fibrous meshwork and the fat cells. SMAS blood circulation expanded subcutaneously without perforating the fibro-muscular septa.

The NLF has a recognizable condensed cheek SMAS structure and represents the transition zone between the two SMAS types. Specimen-specific morphological differences necessitate individual planning and area-specific surgical procedures.