Needle‐free pneumatic injection device; histologic assessment using a rat model and parameter comparison in predicting collagen synthesis degree

Background Needle‐free pneumatic injections have been recently introduced to the field of dermatology to inject such substances as hyaluronic acid. However, data on the influence of various pneumatic injection parameters on collagen synthesis are lacking. Objective Compare the effect of diameter, pressure, and volume of a pneumatic injection jet on collagen synthesis and fluid dispersion pattern using a rat model. Investigate if the total work force of the injection jet is useful in predicting the degree of collagen synthesis. Materials and Methods We injected fluid with 1 mg/ml of hyaluronic concentration to adult rats. Different injection pressures and volumes were tested using devices with nozzles of different diameters. Collagen synthesis areas were then measured, and statistical analyses were performed. Results The area of collagen fibers increased for up to two months. The injection pressure and volume did not correlate with the degree of collagen synthesis. The nozzle diameter showed a significant after two and four weeks of injection. The total work force correlated with collagen synthesis 2, 4, and 8 weeks post‐injection. (P = 0.043, 0.027, and 0.000, respectively). Conclusion Collagen formation is more prominent 2 months post‐hyaluronic acid injection than after 1 month when using a needle‐free pneumatic injection device. The total work force, which is affected by both the nozzle diameter and injection pressure, can be helpful in predicting the degree of collagen synthesis. Lasers Surg. Med. 51:278–285, 2019. © 2019 Wiley Periodicals, Inc.