Effectiveness of Botulinum Toxin Type A Injection on Scars: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Background: Scars can cause pain, long-term physical dysfunction, and psychological harm. Botulinum toxin type A (BoNT-A) is one treatment choice for scars, but further evidence is needed to confirm its efficacy. Methods: This systematic review included randomized controlled trials that investigated the effectiveness of BoNT-A on scars. The mean and standard deviation for the Vancouver Scar Scale, Stony Brook Scar Evaluation Scale, visual analog scale for appearance evaluation, visual analog scale for scar pain evaluation, and scar width were extracted for subgroup analysis. Results: Twenty-one randomized controlled trials were included. The BoNT-A group had a lower Vancouver Scar Scale score than the saline group (standardized mean difference, -0.73; 95 percent CI, -1.12 to -0.35; p = 0.0002) but a higher score than the steroid group (standardized mean difference, 0.85; 95 percent CI, 0.27 to 1.43; p = 0.004). The BoNT-A group exhibited a higher Stony Brook Scar Evaluation Scale grade than the saline group (standardized mean difference, 1.42; 95 percent CI, 0.83 to 2.00; p < 0.00001). The visual analog scale for appearance evaluation revealed higher scores in the BoNT-A group than in the saline group (standardized mean difference, 1.14; 95 percent CI, 0.69 to 1.60; p < 0.00001). As for pain evaluation, the BoNT-A group had a lower visual analog scale score than the steroid group (standardized mean difference, -2.57; 95 percent CI, -4.40 to -0.74; p = 0.006). Furthermore, scar width was significantly shorter in the BoNT-A group than in the control group (standardized mean difference, -1.11; 95 percent CI, -1.38 to -0.83; p < 0.00001). Conclusions: BoNT-A is more effective in treating scars than saline, although steroids may exhibit higher potency. Therefore, it can be considered an alternative in patients not amenable to steroid treatment.