VISCOELASTIC PROPERTIES OF THE SUPERFICIAL MUSCULOAPONEUROTIC SYSTEM (SMAS) - A MICROSCOPIC AND MECHANICAL STUDY

A study was undertaken to determine the physical properties and micros copic structure of the superficial musculoaponeurotic system (SMAS) ti ssue. Forty virginal specimens and eight reoperated specimens were exa mined. The following findings were discovered. 1) Microscopic appearan ce shows the SMAS to consist of collagen fibers, a relatively high con centration of elastic fibers interspersed with fat cells. 2) On scanni ng electron microscopy, the virginal SMAS shows the collagen fibers to have a similar convoluted appearance as in the dermis. There is some evidence of parallelization of the collagen fibers in the reexcised SM AS specimens. 3) Mechanical testing (Instron) demonstrates that both t he SMAS and preauricular skin were subjected to a series of loading/un loading tests at various rates, amplitudes, and stress relaxation test s. Both sets of specimens indicated definite viscoelastic properties. Although the mechanical behavior of both tissues was somewhat similar, the viscoelastic effect of the SMAS was less pronounced. A slackening effect of the SMAS indicated a gradual expansion of the SMAS postoper atively. These results could provide some indication of the long-term effects of SMAS surgery.