Dallas, Texas From the Department of Plastic Surgery, University of Texas Southwestern Medical Center.
Plast Reconstr Surg. 2011 Sep;128(3):757-764. doi: 10.1097/PRS.0b013e3182221354.
The superficial musculoaponeurotic system (SMAS) has inherent viscoelastic properties, although the optimal tension levels to minimize tissue relaxation have not been defined. This study evaluated the viscoelastic properties of the SMAS within the biomechanical parameters of the high-SMAS rhytidectomy.
Patients (n = 30) underwent a high-SMAS face lift performed by the senior author (F.E.B.) with intraoperative tension at the superior (preauricular) and inferior (mastoid) points of SMAS fixation sequentially measured with a tensiometer. Fresh samples of lateral, preparotid SMAS were then harvested and evaluated ex vivo for bursting strength, stress relaxation, and creep.
The force applied to the superior, preauricular SMAS intraoperatively (7.21 ± 0.87 N) was significantly lower than that of the inferior mastoid point of fixation (9.59 ± 1.8 N) (p < 0.001). The bursting force of the SMAS was 55.7 N, with the average bursting pressure of 224.97 PSI. The in vivo force applied to the SMAS was found to be only 15 percent of its total bursting strength. The deformational load of the high-SMAS face lift caused only a 14 percent creep in the tissue ex vivo.
The in vivo tension in a high-SMAS face lift is predictable, with the force applied to the mastoid point being significantly greater than that of the superior preauricular point. This intraoperative force is only a fraction of the tissue's inherent bursting strength, contributing to the minimal stress relaxation and creep observed in this study. These biomechanical properties likely contribute to the effective and long-lasting correction of facial aging with the high-SMAS technique.
CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.
尽管尚未确定最小化组织松弛的最佳张力水平，但表浅肌肉腱膜系统 (SMAS) 具有固有的粘弹性。本研究评估了在高 SMAS 除皱术中生物力学参数范围内 SMAS 的粘弹性。
患者（n=30）接受了由资深作者（F.E.B.）进行的高 SMAS 面部提升术，术中通过张力计依次测量 SMAS 固定的上（耳前）和下（乳突）点的张力。然后采集外侧、腮腺前 SMAS 的新鲜样本，并在体外评估其爆裂强度、应力松弛和蠕变。
术中上耳前 SMAS 所施加的力（7.21±0.87N）明显低于下乳突点固定的力（9.59±1.8N）（p<0.001）。SMAS 的爆裂力为 55.7N，平均爆裂压力为 224.97PSI。SMAS 所受的体内力仅为其总爆裂强度的 15%。高 SMAS 面部提升术的变形负荷仅导致组织体外 14%的蠕变。
高 SMAS 面部提升术中的体内张力是可预测的，乳突点的力明显大于耳前上点的力。这种术中力仅为组织固有爆裂强度的一小部分，这有助于解释本研究中观察到的最小应力松弛和蠕变。这些生物力学特性可能有助于高 SMAS 技术对面部衰老的有效和持久矫正。
临床问题/证据水平：治疗，IV。
