Does injection pattern matter in upper face BoNT-A application? A prospective split-face andomized trial comparing linear and spot technique

Background: Although the efficacy of botulinum toxin type A (BoNTA) has been shown to vary depending on injection layer, reconstitution volume, and BoNTA formulation, the effect of injection pattern has rarely been mentioned. The authors compared the therapeutic effects in patients treated with BoNTA with retrograde linear and traditional spot injection techniques. Methods: Twenty-eight participants were enrolled in a split-face, patient-blinded randomized clinical trial. Each patient received BoNTA injected with linear injection technique on one side and with spot injection technique on the other side. Outcomes included wrinkle improvement rates (WIRs) of the 2 injection techniques determined by wrinkle scores derived from an Antera 3-dimensional camera, muscle activity assessed by ultrasound, and patient-reported pain rating on a numeric rating scale. Results: All participants completed the study. For forehead wrinkles, WIR on the linear side was significantly larger than that on the spot side at 1 week and 1 month ( P < 0.02). For glabellar wrinkles, WIR on the linear injection side was significantly larger than that on the spot side at 1 week ( P = 0.04). However, for periorbital wrinkles, WIR on the spot side was significantly larger than that on the linear side at 1 week ( P < 0.03). No significant difference was observed between the injection patterns in terms of muscle contraction and numeric rating scale pain scores. Conclusions: Compared with the traditional spot injection, retrograde linear injection was superior in reducing forehead lines and glabellar lines, but less effective in reducing periorbital lines when identical dosages were injected. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, II.