Is It Possible to Measure the Amount of the SMAS Face Lift According to Facial Vectors?

Since the initial description of the importance of the superficial musculoaponeurotic system (SMAS) in the face-lift procedure, surgical treatment of the facial aging through SMAS face lift evolved to be less invasive, mainly because of potential temporary or permanent facial nerve damage1 with disturbance of the normal function of facial muscles, which could require reconstruction such as the transplantation of subunits of the latissimus dorsi muscle.2 When treatment of the SMAS involves plication, there is a consensus that the SMAS face lift must be performed superiorly and posteriorly; regardless of the technical choice, the concept of the facial vectors is well established.1 The main superior vectors are performed parallel to the body of the mandible, at the level of the projection of the zygomatic arch, and the posterior ones are performed along the projection of the ramus of the mandible. The convergence of these two vectors generally occurs at the preauricular area in the level of projection of the root of the helix, resulting in an inverted-L shape or a 7 shape with an oblique final vector.3 Considering all of the different types of faces and deformities, the distance between the two horizontal and vertical vectors and, consequently, the amount of SMAS lift, will vary according to each patient.1,3 Real et al. described a technique of frontotemporal minilifting using the concept of facial vectors and, based on anatomical points, quantified the amount of eyebrow tail suspension.4 For the past 10 years, the preferred technique for face lift in our group has been the plication of the SMAS, with its imbrication to return volume to the malar area. After skin dissection, the SMAS is marked as described above with two parallel 7-shaped figures, according to the maximum traction possible by both main vectors (Fig. 1).Fig. 1.: Vectors of the two parallel 7-shaped figures at the third middle of the face (arrow indicates the oblique final vector according to the maximum traction of the SMAS).Considering the theory of vector sum, it can be noted that the arrangement of the vectors as two 7-shaped figures enables calculation of the difference between the areas of each one, through the parallelogram law. The so-called parallelogram law gives the rule for vector addition of two or more vectors. For two vectors a and b, the vector sum a + b is obtained by placing them head to tail and drawing the vector from the free tail to the free head. In Cartesian coordinates, vector addition can be performed simply by adding the corresponding components of the vectors; therefore, A = (a1, a2, …, an) and B = (b1, b2, …, bn).5 Therefore, this rule could be applied when there is an overlapping of two geometric figures (Fig. 2). In theory, this numeric value could direct surgeons to estimate the amount of SMAS traction in each patient and then evaluate the effectiveness of the procedure. This idea has been developed and incorporated in the routine of our face-lifting procedures and the results will be presented soon.Fig. 2.: Overlapping of the two geometric figures according to the parallelogram law. The difference between their areas will predict the total amount of lifting.DISCLOSURE The authors declare that they have no commercial interest in the subject of study or in the source of any financial or material support. Marcus Vinicius J. Barbosa, M.D., Ph.D.School of MedicineMorphofunctional LaboratoryMorphofunctional Laboratory Tiago Bianchi, Ph.D.IBM Fabio X. Nahas, Ph.D., M.B.A.Lydia M. Ferreira, M.D., Ph.D.Department of SurgeryDivision of Plastic SurgeryFederal University of São PauloSão Paulo, Brazil