Dynamic Evaluation of Glabellar Area Muscles Movement and Skin Displacement Using 3D Skin Displacement Vector Analysis.

[BACKGROUND] Three-dimensional (3D) skin displacement vector analysis method provides a deeper understanding of dynamic muscle anatomy. Understanding the dynamic muscle anatomy in the glabellar area during frowning can facilitate safer and effective botulinum toxin injections for treating glabellar wrinkles.

[OBJECTIVE] We aimed to investigate the skin displacement patterns of the glabellar area and adjacent skin during contraction of the glabellar muscles using 3D skin vector displacement analysis.

[METHODS] Twenty-nine healthy individuals (26 female, 3 male; median age 40.5 years) participated in the study. Photographs of the face were taken at rest and during maximal contraction of the glabellar muscles. Each expression image was aligned to its respective static image to compute the differences in the skin position.

[RESULTS] Two skin displacement patterns were identified during frowning: lateral pattern (89.66%), in which main skin vector displacement located on the eyebrow area and central pattern (10.34%), in which skin vector displacement mostly located between eyebrows. 62.07% showed asymmetric skin displacement. Analysis of the glabellar patterns showed that the 'U', '11', 'X', and 'π' patterns were observed in 38%, 38%, 14%, and 10% of cases, respectively, with corresponding skin vector displacement angles of 48°, 32°, 74°, and 24°. Additionally, 20.69% of subjects exhibited upward skin movement in the medial frontalis area during frowning. In 48% of subjects, the lateral and inferior portions of the orbicularis oculi muscle contracted, along with the upper medial portion.

[CONCLUSION] This data will serve as an important guide for Botulinum Toxin treatment of glabella wrinkles in Korean patients.