Analysis of Dermal Thickness Across 10 Areas and Injection Depth After Polynucleotide Injection Using Rejumate Automatic 0.8-mm 9-pin Injector on the Face Using 33-MHz Sonography

Background: Automated injection devices are becoming essential tools in aesthetic medicine, offering precision and consistency in treatments such as polynucleotide (PN) injections for skin rejuvenation. This study aimed to analyze the dermal thickness across facial regions and evaluate the consistency of injection depth achieved with the Rejumate automatic injector. Methods: A total of 31 patients (average age 48.2 y; 4 men and 27 women) underwent dermal thickness measurements using high-resolution 33-MHz ultrasound in 11 facial regions, including the forehead, temple, orbital rim, lower eyelid, malar, anterior cheek, lateral cheek, posterior cheek, jawline, and chin. Each patient then received a standardized 2-mL PN injection using the Rejumate injector with a 0.8-mm needle across 317 individual points. Injection depth, distribution, and consistency were measured and analyzed. Results: The average dermal thickness across regions ranged from 0.53 (lower eyelid) to 1.18 mm (temple and posterior cheek). The Rejumate injector demonstrated a high degree of consistency, achieving an average injection depth of 0.55 mm (SD = 0.13 mm), with a median depth of 0.54 mm. The depth range (0.29–0.99 mm) and interquartile range (0.17 mm) indicated controlled depth with minimal variability. Conclusions: The Rejumate automatic injector reliably delivers PN at a controlled depth, showing minimal variability across injections. This precision supports improved safety and efficacy in PN delivery, providing a valuable reference for clinical application in aesthetic treatments. Given the anatomical differences in dermal thickness across facial regions, this standardized approach may optimize outcomes and increase patient satisfaction.