Prospective Analysis of the Effectiveness of Targeted Botulinum Toxin Type A Injection Using an Ultrasound-Guided Single-Point Injection Technique for Lower Face Contouring

<b>Background</b>: Botulinum toxin type A (BoNT-A) injection is widely used for masseter hypertrophy. Traditional BoNT-A injection methods often incorporate landmark-guided blind injections, which approximate the shape of the masseter muscle inject across various points. Conversely, ultrasound (US)-guided injection techniques offer real-time visualization and dynamic monitoring, enhancing accuracy. <b>Patients and Methods</b>: 50 patients who underwent BoNT-A injections were included in this trial. One on the face side received a landmark-guided injection, and the other side was treated with a US-guided injection. Initial and post-procedure measurements of muscle thickness at the upper, middle, and lower regions were collected using ultrasound. <b>Results</b>: Both methods led to a significant reduction in muscle thickness one month after injection. In the upper area, the absolute difference in muscle thickness between the two methods was observed as a mean ± standard deviation (SD) value of 0.37 ± 0.0314 (<i>p</i> < 0.0001), indicating a superior effect with US-guided injection. Similarly, in the middle area, the mean ± SD difference was 0.41 ± 0.0608 (<i>p</i> < 0.0001) and in the lower area, the mean ± SD difference was 0.24 ± 0.0134 (<i>p</i> = 0.0004). <b>Conclusions</b>: This study demonstrated that the US-guided single-point injection technique is a more effective and accurate method for BoNT-A injection compared to the conventional method.