title: An anatomical study of the risorius in Asians and its insertion at the modiolus.
abstract: OBJECTIVE
  Detailed explanations of the insertion, interaction patterns, and arrangement of the risorius muscle fibers at the modiolus have still not been clearly shown. The aim of this study is to clarify the arrangement of the risorius muscle by means of topographic examination, and to evaluate the anatomical variations in its attachments and pattern of shape to other perioral muscles, and eventually to understand the various features of the facial animation of Asians.
  
  
  METHODS
  Eighty embalmed Korean and Thai adult hemifaces from cadavers of both genders were dissected in this study. Detailed dissection at the modiolus revealed the insertion of the risorius muscle in relation to its attachments and fiber interaction forms.
  
  
  RESULTS
  When categorized into three common anatomical types--zygomaticus risorius (ZR), platysma risorius (PR), and triangularis risorius (TR). PR was most common with 45 % (36 cases) frequency. Risorius muscle also inserted into the modiolus in three distinct layers in relation to the depressor anguli oris: superficial, flush, and deep. Superficial attachment was most commonly found with 56.3 % (45 cases) frequency.
  
  
  CONCLUSIONS
  These results will provide critical information for future planning and performing of reconstructive, reanimation, and cosmetic surgical procedures for cases such as developmental defect, facial trauma, facial muscle paralysis, and restoring the natural personal appearances.
authors: Division in Anatomy and Developmental Biology, Department of Oral Biology, Human Identification Research Center, BK21 PLUS Project, Yonsei University College of Dentistry, Seoul, South Korea.
authors: Hong-San
authors: HS
authors: Kim
authors: Calvin
authors: C
authors: Pae
authors: Jung-Hee
authors: JH
authors: Bae
authors: Kyung-Seok
authors: KS
authors: Hu
authors: Brian M
authors: BM
authors: Chang
authors: Tanvaa
authors: T
authors: Tansatit
authors: Hee-Jin
authors: HJ
authors: Kim
mesh_terms: D000368:Aged; D044466:Asian People; D002102:Cadaver; D004210:Dissection; D005145:Face / Q000033:anatomy & histology; D005152:Facial Muscles / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D008297:Male