Clinical and histological evaluation of microneedle fractional radiofrequency treatment on facial fine lines and skin laxity in Koreans

Facial wrinkles and sagging are the most visible signs of aging and can cause profound distress. Microneedle fractional radiofrequency (MFR) is a minimally invasive procedure, which utilizes both microneedling and radiofrequency energy to rejuvenate the skin.


| INTRODUC TI ON
Aging is inevitable but hits one hard when it is openly visible.
Regardless of one's ethnicity and skin color, many express concerns over their facial wrinkles and laxity and unsurprisingly, the demand for facial rejuvenation is high. Minimally invasive aesthetic procedures encompassing both energy-based devices and non-energybased practices such as microneedling have become increasingly popular and are currently much sought-after. [1][2][3][4][5][6] Radiofrequency enables non-operative skin tightening by delivering thermal energy to the reticular dermis. 7 It is chromophoreindependent (less likely to cause pigmentary changes), which makes it particularly favorable in Asians over lasers. 8 Microneedle fractional radiofrequency (MFR) is a novel technology with additional benefit in that it selectively delivers RF through insulated microneedles. 3 The bipolar MFR adopted in this study was equipped with a temperature sensor, which enables optimal thermal doses to be delivered to the target site. 2,9 The main objective of this study was to analyze the efficacy and safety of a temperature-controlled bipolar MFR device applied to improve facial fines lines and skin laxity in Koreans.

| Study design
A retrospective chart review was performed over a period of 2 years from January 2020 to December 2021. We compiled and analyzed data from consecutive patients who underwent temperature controlled, bipolar MRF treatment for facial rejuvenation at Arumdaun Nara Dermatologic Clinic. Exclusion criteria were those who received botulinum toxin or filler injection, or any skin rejuvenation treatment within the past 6 months, and during the follow-up period. We reviewed the patients' gender, age, and pre-and post-operative clinical photographs. The results were assessed objectively using serial photography and subjectively according to patient assessments. The principles of the 1975 Declaration of Helsinki were followed. The study was approved by the Institutional Review Board (OC22RISI0112). is built into the device, which allows real-time temperature measurement and delivery of optimal thermal energy to target sites.

| Treatment device and protocol
The procedure was performed with the patient under local anesthesia. A layer of Lidocan cream (96 mg/g of lidocaine, Dae Han New Pharm) was applied over the treatment area, which extended from the nasolabial and melolabial folds (medial) to the preauricular region (lateral) and from the inferior orbital rim (superior) to the submental and submandibular regions (inferior) (Figure 2). After an hour, the area was cleansed with betadine followed by local injection of tumescent fluid (mixture of normal saline 100 cc; 1 mg/ml epinephrine 0.2 cc; 2% lidocaine 10 cc; and 8.5% sodium bicarbonate 1 cc). All subjects received one single-pass treatment with the dermal cartilage at a fixed parameter of 67°C and 3 seconds. After each pulse, the MFR applicator was withdrawn, repositioned, and activated on the next treatment site until the target zone was fully covered. The distance between the insertions was 2-4 mm and treatments were delivered medial to lateral in rows following anatomical margins. The typical number of MFR insertions delivered per subject was 150 on each side. Postoperatively, the treated area was cleansed with isotonic sodium chloride solution and a thin coat of white petrolatum was applied.

| Clinical assessment
Treatment efficacy was assessed by comparing photographs at 4month follow-up with those taken at baseline using a 5-point Global Aesthetic Improvement Scale (GAIS) (5-"very much improved", 4-"much improved", 3-"improved", 2-"no change", 1-"worse"). The grading was performed by 2 independent, blinded, board-certified dermatologists. Side effects up to 6 months after the procedure were recorded. Patients were followed up after the procedure, and their outcomes were evaluated by asking them to rate their overall satisfaction using the following scale: "greatly satisfied", "satisfied", "slightly satisfied", or "not satisfied".
F I G U R E 1 Temperature-controlled bipolar MRF device (ProfoundTM system, Candela Medical) adopted for the study.

| Histologic assessment
Skin specimens obtained from volunteers before, immediately and 4 months after bipolar MFR treatment were sent off to a boardcertified dermatopathologist for staining and assessment, using conventional optical microscopy. Tissues were stained with hematoxylin and eosin (H&E), Masson's trichrome, and Victoria blue. Three individuals underwent 3 biopsies (before, immediately after and 4 months after the procedure) and 8 had 2 biopsies (before and at 4 months follow-up) a few centimeters ahead of the preauricular area.

| Statistical analysis
All statistical analyses were conducted using PASW version 18.0 (IBM). Descriptive statistics are presented as both numbers and percentages of the patients or as means and standard deviations.

| RE SULTS
Participants' characteristics and outcomes are summarized in Table 1. A total of 15 individuals who underwent bipolar MFR treatment once and made regular follow-up visits were included in the study.
The mean age of the study population was 44.4 years with a range of 23-67 years. The Fitzpatrick skin types were III or IV.
In the biopsy samples taken from the preauricular region, H&E staining showed atrophic and flat epidermis before treatment and thicker epidermis with papillae at 4 months follow-up after MFR ( Figure 4A,B). Partial denaturation of the initially disorganized colla- All reported pin-point bleeding and mild to moderate erythema and edema after the procedure (Figure 7), which resolved within days. Serious adverse events such as skin burn, bullae, scarring, and hypo-or hyper-pigmentation were not observed in this study.

F I G U R E 2
Schematic representation of the insertion sites. The paired electrode tips were inserted at an interval of 2 to 4 mm apart in the area shown. A total of 150 insertions were administered per side to this patient. The insertion sites typically involved the nasolabial and melolabial folds (medial) to the preauricular region (lateral) and from the inferior orbital rim (superior) to the submental and submandibular regions (inferior).

Age (years)
44.4 ± 13.6 Among the various signs of aging, skin laxity, mostly seen on the lower two thirds of the face, is the most difficult and troublesome to man-

Number of subjects (%)
age. An FDA-approved temperature-controlled bipolar MFR device known to electively deliver thermal energy to the reticular dermis and While the device offers two types of cartilage (i.e., Dermal and SubQ cartilage), we relied solely on the Dermal cartilage to ensure uniform treatment with minimal variability between subjects.
Our settings delivered energy necessary for the reticular dermis to reach a temperature of 67°C for 3 seconds, which is known to be optimal for partial collagen degeneration and subsequent neocollagenesis. 10,11 The increase in dermal collagen and elastin was the As for the treatment site, we recommend treatment on facial areas where the skin is relatively thick (i.e., cheek, submentum). In our case, the inferior orbital rim was set as the superior boundary to avoid microneedling the thin-skinned temple and the lower eyelid. At these sites, the microneedles often touch the bone, which can be problematic as the needles are easily bent from the impact. Clinical improvement extending beyond the treatment area has been reported after the use of F I G U R E 4 In the biopsy samples taken from the preauricular region, H&E staining shows atrophic and flat epidermis before treatment (A) and thicker epidermis with papillae at 4 months follow-up after MFR (B) (x40).

CO N FLI C T O F I NTE R E S T
None to declare.

DATA AVA I L A B I L I T Y S TAT E M E N T
The data that support the findings of this study are available from the corresponding author upon reasonable request.