Abstract
Regional differences in the integument of the body are explained, at least in part, by differences in fascial arrangements. In the face, where the skin is more mobile due to the action of the underlying facial muscles, fascial organisation is important for support and separation of muscle groups. This study used bequeathed cadaver material to investigate a current model of the SMAS proposed by Macchi et al., the original boundaries of which were explored and extended using both histology and gross dissection. As a clearly identifiable structure spanning the lateral and midface, the SMAS in the specimen supported the model proposed by Macchi et al. The three main findings that support the model were the layered morphological appearance of the SMAS, its progression from fibrous to aponeurotic in a lateral to medial direction, and the enveloping of the zygomaticus musculature. Extension beyond the proposed model into the temporal region was observed, but nasal and forehead regions showed no evidence of SMAS, while its presence in the cervical platysma region remained inconclusive. Fascial and soft tissue variability was considerable within facial regions of the examined specimen, helping to explain the debate around the SMAS in the literature.
Highlights
In 1976, a superficial musculoaponeurotic system (SMAS) was described in the parotid and cheek regions of the face, dividing superficial and deep adipose tissue [1]
Gross dissection of the buccal region revealed the SMAS, the nasolabial fold region showed no evidence of SMAS when explored by either method
The SMAS was superficial to two distinct fibrous layers, the deep platysma fascia and the parotid fascia
Summary
In 1976, a superficial musculoaponeurotic system (SMAS) was described in the parotid and cheek regions of the face, dividing superficial and deep adipose tissue [1]. The definitions and descriptions of the SMAS have been the subject of much debate in the literature. Terminology, definitions, and descriptions of SMAS morphology are inconsistent [4,5,6,7], with some studies even questioning its existence [8, 9]. The existence of the SMAS separate from the parotid fascia was more readily agreed upon [7, 10, 11], earlier studies remained inconclusive [9, 12]
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