In Vivo Histological Evaluation of Non-Insulated Microneedle Radiofrequency Applicator With Novel Fractionated Pulse Mode

December 2013 | Volume 12 | Issue 12 | Original Article | 1430 | Copyright © 2013

Yoram Harth MD FAADa,b and Ido Frank BSc MBAb

aMedical OR Center, Herzlya Pituach, Israel
bEndyMed Medical, Cesarea, Israel

Abstract

INTRODUCTION: Microneedle radiofrequency is a novel method that allows non-thermal penetration of the epidermis followed by RF coagulation in selected depth of the dermis surrounded by zone of non-coagulative volumetric heating. The first generation of Microneedle RF applicators used insulated needles. These treatments were limited by a few factors, including low volume of dermal heating, lack of effect in the papillary dermis and pinpoint bleeding during the treatment. The system tested in this study (EndyMed PRO, Intensif applicator, EndyMed Medical, Cesarea, Israel) utilizes special extra sharp tapered non-insulated microneedles and a special pulse mode, allowing full coagulation during treatment and higher effective volume of dermal heat.
METHODS: After Ethics Committee approval, one female pig (Type Large white X Landrace, 34 Kg) was chosen for the study. The animal was anesthetized using Ketamine, Xylazin and Isofluran. The EndyMed PRO, Intensif applicator (was used for treatment with different needle depth penetration (1mm-3.5 mm) and in multiple energy settings. Six mm punch biopsies were harvested for histological analysis at the following time points: immediately after the treatment, 4 days after the treatment and 14 days after the treatment. H&E and Masson-Trichrome stains were processed.
RESULTS: Visual inspection of the treated skin, immediately after the treatment, revealed arrays of pinpoint erythematous papules surrounded by undamaged epidermal tissue. Treatment field showed no sign of bleeding. Mild to moderate Erythema and Edema developed a few minutes after the treatment, varying according to the total energy delivered. The histologies taken 4-day after therapy showed in all energy settings, dry micro crusts over the treatment zones, with full healing of epidermis. In the 14-day specimens there was a replacement of the crusts/debris by a normal looking stratum corneum with complete healing of epidermis and dermis.
DISCUSSION: The current in vivo study confirms that the EndyMed PRO Intensif applicator effective and predictable tool to create cylindrical micro zones of coagulation in the papillary and reticular dermis with minimal damage to the epidermis. The histologies taken 4 days and 14 days after treatment show rapid epidermal renewal with predictable volume of coagulation in dermis related to the length of the needle and the power used. Coagulation of capillaries during treatment allows a dry treatment field. The predictability of the effect and minimal downtime may offer a significant advantage over treatments with ablative fractional lasers of insulated RF microneedles.

J Drugs Dermatol. 2013;12(12):1430-1433.

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INTRODUCTION

Traditional skin resurfacing CO2 laser devices, though highly effective in tissue coagulation, are associated with prolonged recovery time, bleeding, oozing, and risk of post treatment hyper or hypopigmentation.1-5 In addition, these lasers are very problematic in treating darker skin types or sensitive Asian skin. In “fractional” laser or radiofrequency skin resurfacing treatments, thermally ablated or coagulated microscopic zones of epidermis and dermis are spaced in a grid over the skin surface; the non ablated zones in the uninjured surrounding tissue serve as a reservoir of cells that accelerate and promote rapid healing6. The use of radiofrequency (RF) overcomes some of light based disadvantages offering enhanced tissue penetration independent of skin color. Fractional skin resurfacing using multisource RF generators and 112 flat micro electrodes, has been shown to ablate the epidermis to a depth of 100-150 micron with simultaneous volumetric heating of the dermis to a depth of 2.8 mm achieving good clinical results and safety profile.7,8,9,10 Microneedle radiofrequency allows non-thermal penetration of the epidermis followed by RF coagulation in selected depth of the dermis. Hantash et al,11,12 delivered RF energy for 4 seconds, through ten, partially insulated, 6 mm long, micro-needles inserted in an 20 degrees angle into the skin. To prevent pain and epidermal damage, the treatment required local infiltration with lidocain and active epidermal cooling. Histological examination showed, RF thermal zone (RFTZ) through day 28 post-treatment but were replaced by new dermal tissue by 10 weeks.

Another type of RF microneedles delivery system uses 3.5 mm long microneedles inserted vertically into the skin, allowing a significant reduction in pain. The first generation of vertically inserted RF microneedles were insulated allowing only a small volume of

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