Histometric Analysis of Skin-Radiofrequency Interaction Using a Fractionated Microneedle Delivery System

BACKGROUND: Fractionated microneedle radiofrequency (RF) devices have been reported to be effective in treatment of various dermatologic disorders. OBJECTIVES: To analyze histometric changes in skin-RF interactions using a fractionated microneedle delivery system. MATERIALS AND METHODS: RF energies were delivered using a fractionated microneedle device to an in vivo minipig model with penetration depths of 0.5, 1.0, 1.5, 2.0, 2.5, and 3.5 mm; RF conduction times of 20, 50, 100, and 1,000 ms; and energy levels of 5.0, 10.0, 20.0, 25.0, 37.5, and 50.0 V. RESULTS: Immediately after treatment, skin samples showed that the RF-induced coagulated columns in the dermis formed a cocoon-shaped zone of sublative thermal injury. Four days after the treatment, skin specimens demonstrated reepithelialization, and the dermal RF-induced coagulated columns showed mixed cellular infiltration, neovascularization, and granulation tissue formation. Microneedle depth and RF conduction times, but not energy level, significantly affected histometric values of RF-induced dermal coagulation. Microneedle RF treatment affected adnexal structures by coagulating follicular epithelium and perifollicular structures. CONCLUSIONS: Our data may be of use as an essential reference for choosing RF parameters in treatment of various skin conditions.