title: Alteration of Skin Mechanical Properties in Patients Undergoing Botulinum Toxin Type A Injections of Forehead Rhytides.
abstract: BACKGROUND
  Although application of botulinum toxin type A (BTX-A) for the treatment of forehead rhytides has become very popular, the effects of its intramuscular injections on the skin mechanical properties remain unclear.
  
  
  OBJECTIVE
  We prospectively investigated the alterations in the mechanical properties of the skin of patients who received intramuscular injections of botulinum toxin A (BTX-A) for forehead rhytides and compared two injection doses.
  
  
  METHODS
  Of the 42 enrolled patients, one randomly assigned half received intramuscular injections of two units (group I), and the other half received four units (group II) of BTX-A in each injection point. The baseline and post-treatment skin mechanical parameters, including gross elasticity (R2), net elasticity (R5), viscoelastic ratio (R6) and biological elasticity (R7), were measured using the Cutometer(®) and compared.
  
  
  RESULTS
  Treatment with BTX-A resulted in significant overall alterations in the mechanical properties of skin at the injection sites of both treatment groups during the 16-week period, and no significant differences were observed between groups. Significant decreases in biological elasticity, net elasticity and viscoelasticity properties were observed at 2 weeks follow-up and began to recover at that time. All of the skin mechanical properties recovered to baseline levels by 16 weeks of follow-up in both dosage groups, which indicates that the higher dosage (4 units) did not delay relapse compared to the two-unit dosage.
  
  
  CONCLUSIONS
  We concluded that intramuscular injections of BTX-A significantly regulated the gross elasticity, net elasticity, functional elasticity and viscoelastic elasticity at the injection point over a radius of 1.5 cm at 2, 4 and 8 weeks follow-up. The alteration in the skin measurements had completely diminished by the 16-week follow-up.
  
  
  METHODS
  This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .
authors.affiliation: Department of Plastic and Reconstructive Surgery, Shanghai Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China.
authors.forename: Peiru
authors.initials: P
authors.lastname: Min
authors.affiliation: Department of Plastic and Reconstructive Surgery, Shanghai Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Plastic and Reconstructive Surgery, Marche Polytechnic University Medical School, University Hospital of Ancona, Ancona, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Grassetti
authors.affiliation: Department of Plastic and Reconstructive Surgery, Shanghai Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China.
authors.forename: Aurelia Trisliana
authors.initials: AT
authors.lastname: Perdanasari
authors.affiliation: Department of Plastic and Reconstructive Surgery, Marche Polytechnic University Medical School, University Hospital of Ancona, Ancona, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Torresetti
authors.affiliation: Department of Plastic and Reconstructive Surgery, Shanghai Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China.
authors.forename: Zheming
authors.initials: Z
authors.lastname: Pu
authors.affiliation: Department of Plastic and Reconstructive Surgery, Shanghai Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Shanghai Tida Medical Aesthetic Hospital, Shanghai, China.
authors.forename: Sheng
authors.initials: S
authors.lastname: Han
authors.affiliation: Plastic and Reconstructive Surgery Unit, Hospital of Pisa, Pisa, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Marsili
authors.affiliation: Department of Plastic and Reconstructive Surgery, Shanghai Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China. zhangyixin6688@hotmail.com.
authors.forename: Yi Xin
authors.initials: YX
authors.lastname: Zhang
authors.affiliation: Department of Plastic and Reconstructive Surgery, Marche Polytechnic University Medical School, University Hospital of Ancona, Ancona, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: di Benedetto
authors.affiliation: Plastic Reconstructive and Aesthetic Surgery Unit, Villa Salaria Clinic, Rome, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Lazzeri
mesh_terms: D019274:Botulinum Toxins, Type A / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D004954:Esthetics; D005260:Female; D005500:Follow-Up Studies; D005546:Forehead; D006801:Humans; D007273:Injections, Intramuscular; D008875:Middle Aged; D009465:Neuromuscular Agents / Q000008:administration & dosage*; D011446:Prospective Studies; D018570:Risk Assessment; D012867:Skin / Q000187:drug effects*; D015595:Skin Aging / Q000187:drug effects*; D016896:Treatment Outcome
chemical_list: D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A
keywords: Botulinum toxin; Cutometer; Forehead rhytides; Intramuscular injections; Skin mechanical properties