Comparative study of the efficacy of three versus four botulinum toxin type A injection sites to treat crow’s feet lines in Vietnamese patients: A retrospective cohort study

Botulinum toxin type A is frequently used to treat crow’s feet lines. However, the optimal dose and injection sites are still controversial. The objective of this study was to compare the efficacy of different botulinum toxin type A injection patterns for the treatment of crow’s feet. This single-center, retrospective, cohort study was conducted at the National Hospital of Dermatology. Sixty patients with crow’s feet were recruited and randomly assigned in a 1:1 ratio to receive botulinum toxin type A using either a three-point or a four-point intramuscular injection technique. The treatment efficacy was assessed based on the changes in the Crow’s Feet Grading Scale score at 1, 4 and 16 weeks after treatment. After treatment, the average Crow’s Feet Grading Scale score was significantly decreased compared with the pretreatment score at all timepoints (1, 4, and 16 weeks) in both states (dynamic and static). The average subjective patient-rated satisfaction scores after treatment were significantly higher in the four-point injection group than the three-point injection group (P=0.028). The adverse events were post-injection bruising in three patients and a feeling of eyelid tightness in three patients. Botulinum toxin type A injection is an effective treatment for crow’s feet. Adding a fourth injection maintains the same therapeutic effect and does not increase adverse effects. Patients with lower-fan crow’s feet patterns may benefit more from four-point injection therapy. However, the present findings require confirmation in studies with larger sample sizes, longer follow-up times, and different botulinum toxin type A doses.