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

Although the efficacy of botulinum toxin type A (BoNT-A) has been shown to vary depending on injection layer, reconstitution volumes, and BoNT-A formulations, the impact of injection patterns has been rarely mentioned. This article compared the therapeutic effects in patients treated with BoNT-A with retrograde linear and traditional spot injection techniques.Twenty-eight participants were enrolled in a split-face, patient-blinded randomized clinical trial. Each patient received BoNT-A injected with linear injection technique on one side and with spot injection technique on the other side. Outcomes included the wrinkle improvement rates (WIR) of the two injection techniques determined by the wrinkle scores derived from Antera 3D camera, the muscle activity assessed via ultrasound, and patient-reported pain rating on a numeric pain rating scale (NRS).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 NRS scores.Compared with the traditional spot injection, the retrograde linear injection shows to be superior in reducing forehead lines and glabellar lines, but less effective in reducing periorbital lines when identical dosages were injected.chictr.org.cn: ChiCTR2100046880.