Botulinum Toxin Injection-Site Selection for a Smooth Shoulder Line: An Anatomical Study.

Introduction. This study aimed to improve the accuracy of manual needle placement into the trapezius (TM) for smooth shoulder line. Methods. For macroscopic study 12 TMs and for microscopic study 4 cadavers were detached and then sampled, 1⁎1 cm at the four points from the origin to insertion site (0% at the most lateral point of external occipital protuberance and 100% at the most lateral point of acromion). Results. Most of the nerve endings observed during macroscopic investigations were concentrated in the 60-80% region, and the second most distributed region was the 40-60% region. The microscopic results revealed that the 60-80% region on the reference line had the most dense neuromuscular junction area, while the 40-60% and 80-100% areas were similar in their neuromuscular junction densities. Discussion. These anatomical results will be useful in clinical settings especially for cosmetic surgeons.