Skin Biomechanical Changes after Injection of Onabotulinum Toxin A: Prospective Assessment of Elasticity and Pliability.

OBJECTIVE This study aimed to test the hypothesis that the administration of onabotulinum toxin A will result in an increase in skin pliability and elasticity. STUDY DESIGN A prospective case series with planned data collection in which patients were treated with onabotulinum toxin and assessed at baseline, 2 weeks post-injection, and 2 months post-injection. SETTING A private cosmetic surgery clinic associated with a tertiary academic hospital. SUBJECTS AND METHODS Forty women were prospectively enrolled to receive onabotulinum toxin A into their glabella, forehead, and lateral orbit. Outcomes were assessed at baseline, 2 weeks posttreatment, and 2 months posttreatment using the Cutometer MPA 580. Skin pliability (Uf) and the elastic recoil (Ua/Uf) were recorded as the 2 primary outcome measures. RESULTS There was a significant effect of onabotulinum toxin on skin elasticity (f = 47.8, P = .001) with a mean (+/- SE) increase in elastic recoil of 20% (4.4%) for the glabellar region (P < .001) and 18% (4.0%) for the lateral orbit (P < .0001). There was a significant effect of the treatment on skin pliability (f = 46.9, P < .001) with a mean (+/- SE) increase of 26% (5.4%) for the lateral orbit (P = .001) and 52% (8.3%) for the glabellar region (P < .001). CONCLUSION Injection of onabotulinum toxin into the lateral orbital, forehead, and glabellar regions results in skin that has increased pliability as well as increased elastic recoil. Although this study demonstrates the positive effect of onabotulinum toxin on biomechanical parameters, it is unclear what specific histological changes are occurring within the skin.