The study aimed to assess the effectiveness and safety of a novel monopolar RF device, YOUMAGIC, for skin tightening treatment. The 212 subjects from four hospitals, consisted of 12 males and 200 females aged 30 to 60 years with Fitzpatrick skin types II-V and mild to moderate skin laxity, were included in this study. Subjects were randomly assigned in a 1:1 ratio to the novel RF device (YOUMAGIC, 107 patients) or control (Thermage CPT System, 105 patients), receiving a single treatment. Before their participation, all individuals received detailed information about the study protocol and provided signed informed consent. Digital photographs and VISIA images were captured at baseline, 30, 90, and 180-day post-treatment to evaluate the efficacy of the device for skin tightening. Pain levels were assessed immediately after treatment using a pain measurement scale. Any adverse events (AEs) reported by participants during the study period or noted by the research team were meticulously documented and reviewed by a dermatologist.

This clinical trial took place from May 2023 to February 2024. The study was conducted over a period of 6 months, involving four visits. The first visit, considered the baseline visit, encompassed the screening procedure, obtaining informed consent, and administering the monopolar RF treatment. Subsequent visits, occurring at 30, 90, and 180 days after the baseline visit, were designated as follow-up visits during which the research team evaluated the subjects to assess the outcomes post-treatment. All images were captured using digital photography and the VISIA system (Canfield Scientific Inc., Parsippany, NJ). Global Aesthetic Improvement Scale (GAIS) and Fitzpatrick Wrinkle Classification System (FWCS) were used to evaluate the efficacy. The pain was assessed by numerical rating scale (NRS) immediately after treatment. Any procedure-related side effects were documented and examined.

Inclusion criteria were healthy males and females aged 30–60, diagnosed with mild to moderate sagging skin on the face area (FWCS 3–6 point), defined as Fitzpatrick skin types II-V, and opted for a skin tightening procedure. Subjects were excluded if they had a history of severe skin allergies and currently experiencing skin allergy flare-ups; Sun exposure within the past week; botulinum toxin, fat injections, or other anti-wrinkle treatments in the treatment area within the past 6 months; monopolar radiofrequency or ultrasonic scalpel treatment or having received injections of hyaluronic acid, polylactic acid, or PCL facial fillers in the treatment area within the past 1 year; facial lifting surgery or any facial plastic surgery within the past 1 year; bipolar or multipolar radiofrequency treatments, ablative laser treatments, or other photonic treatments such as facial photo rejuvenation within the past 6 months; deep chemical peel within the past 1 month; inflammatory reactions, significant scars, hemangiomas, severe acne, or other skin lesions that may affect the interpretation of study results in the treatment area; systemic or localized infections; implantable pacemakers, implantable cardioverter-defibrillators, or any other type of implantable electronic devices; metallic implants in the treatment area, such as dental implants; severe obesity (BMI > 30 kg/m2); History of facial nerve paralysis. Women who are pregnant, lactating, or planning to become pregnant during the study period were also excluded.

The treated area was gently cleansed with a mild facial cleanser and a topical anesthetic cream (5% lidocaine) was applied for 30 min. Before the initiation of treatment, the subject was asked to adopt a supine position, the return electrode was positioned beneath each patient’s back to set a monopolar circuit, and RF gel was applied to the treated area to serve as a coupling medium. A 6.78-MHz RF device (YOUMAGIC or Thermage CPT, 900 shots, energy level 2.5-5.0) was used for treatment. During treatment, the treatment head fits on the surface of the body and uses a cooling agent on the body surface. When RF waves are applied, a reverse temperature gradient is created in the skin, maintaining the epidermal temperature below 45 °C and heating the dermal tissue. The procedure lasted 40–60 min, and the RF gel was wiped off and cleaned after treatment.

The primary efficacy endpoint of this study was to evaluate the effective rate of facial wrinkle improvement at 90 days after treatment. The effective rate was characterized by the proportions of subjects who achieved ≤ 3-grade on the GAIS by three independent blinded evaluators using the 5-point GAIS (1 = Very much improved; 2 = Much improved; 3 = Improved; 4 = No change; 5 = Worse), mainly focused on the nasolabial fold.

Secondary efficacy endpoints were comprised of assessments of facial wrinkle improvement rate on GAIS at 30 and 180 days after treatment, FWCS at 30, 90, and 180 days after treatment by independent blinded evaluators, as well as GAIS by both subjects and evaluators at 30, 90, and 180 days after treatment, and NRS at the treatment day. NRS was classified as no pain (0), mild pain (1–3), moderate pain (4–6), and severe pain (7–10).

Safety was assessed by inquiries, subject diary entries of adverse events, laboratory tests, and vital sign checks at each follow-up. Laboratory tests, including complete blood counts, general chemical tests, blood coagulation tests, and blood/urine pregnancy test, were undertaken at the screening visit and then at 180 days (the first two tests). Adverse events (AEs) were evaluated through self-reports and physical examinations at every follow-up, as well as subject diary entries recording adverse reactions within 7 days after treatment [5].

The primary endpoint, the proportion of subjects who achieve ≤ 3-grade on the GAIS, is expected to be 94% in the control group based on previous studies [6,7,8,9]. It is assumed that the therapeutic effect of the treatment group is equivalent to that of the control group, and the non-inferiority margin value is -10%. Thus, calculations showed that at least 89 subjects per group were required to achieve a power of 80% at a 2.5% significance level for assessment of this endpoint. Based on the assumed dropout rate of 15%, a total of 212 subjects were included.

For the primary endpoint assessment, a two-sided 95% confidence interval was calculated for the difference in the improvement rates. Non-inferiority was concluded if the lower limit of the confidence interval was above the non-inferiority margin value (-10%). The t-tests or Wilcoxon signed-rank tests were used to analyze continuous variables. Categorical variables were compared using χ2 tests or Fisher’s exact tests. Data were analyzed using SAS version 9.4.