Immediate and Late Effects of Pulse Widths and Cycles on Bipolar, Gated Radiofrequency-Induced Tissue Reactions in in vivo Rat Skin

Efficacy and safety of fractional microneedle radiofrequency for atrophic acne scars: A real-world clinical study of 126 patients

OBJECTIVE

To analyze the clinical efficacy and safety of fractional microneedle radiofrequency (FMR) for facial atrophic acne scars in a real-world setting.

METHODS

The clinical data of patients with atrophic acne scars who had received FMR therapy from February 2018 to August 2022 were retrospectively analyzed. The improvement of atrophic acne scars was assessed using the ECCA Grading Scale (échelle d'évaluation clinique des cicatrices d'acné), Global Aesthetic Improvement Scale (GAIS), and modified Manchester Scar Scale (mMSS). Adverse reactions during FMR treatment were also recorded. Univariate and multivariate logistic regression analyses were performed to evaluate the efficacy and safety of FMR for atrophic acne scars.

RESULTS

A total of 126 patients with facial atrophic acne scars were included. A total of 590 FMR treatment sessions were accomplished, with each of 82 patients receiving 4 or more treatment sessions, and 1 receiving a maximum of 14 sessions. All patients showed improvement in symptoms after FMR treatment, with moderate to significant improvement (ECCA score reduction of 26%-100%) in 92 (73.0%) patients. As the number of treatment sessions increased, the ECCA score gradually decreased from an average of 85.6 before to 35.0 after FMR. The average scores for distortion, color, and visual analogue scale (VAS) of mMSS all showed certain reductions. The change in GAIS score indicated improvement after treatment, with minimal improvement in 16 patients (12.7%), good improvement in 57 patients (45.2%), significant improvement in 45 patients (35.7%), and optimal improvement in 8 patients (6.4%). The univariate and multivariate logistic regression analyses revealed that the long pulse width and the number of FMR treatment sessions were positively associated with clinical efficacy. Compared to the short pulse-width group (200 ms), the longer pulse-width group (300 ms) (odds ratio [OR] = 8.3, p = 0.003) and the even longer pulse-width group (400-500 ms) (OR = 52.6, p < 0.001) demonstrated stronger efficacies. Patients who received more than three treatment sessions had better outcomes compared to those who received three or fewer treatment sessions (OR = 4.0, p = 0.036). All patients experienced posttreatment transient erythema, but no crusting, infection, or blister. Six cases developed grid-like erythema around 1 month posttreatment and one case experienced hyperpigmentation, both of which resolved within 1-3 months after appropriate management.

CONCLUSION

FMR is a safe and effective treatment modality for improving facial atrophic acne scars, and the number of FMR treatment sessions and pulse width are associated with clinical efficacy.

Effects of Parallel Contact Cooling on Pulsed-Type, Bipolar Radiofrequency-Induced Tissue Reactions in an in vivo Porcine Model

Background

Skin cooling during laser or radiofrequency (RF) treatments is a method to minimize thermal damage to the epidermis, reduce pain, and decrease post-treatment downtime. We evaluated the effect of parallel contact cooling (PCC) on RF-induced thermal reactions in minipig skin in vivo after bipolar microneedling RF treatment.

Methods

RF treatments were administered at frequencies of 0.5, 1, and 2 MHz with single (500 ms), six (1000 ms), and ten (5000 ms) sub-pulse packs to minipig skin with or without PCC. Subsequently, thermometric imaging and histology were used to analyze skin reactions to RF.

Results

Thermometric images showed that PCC promptly lowered skin temperature in the RF-treated area, with this effect persisting for over 60s. Regardless of the PCC, RF treatments lasting for 500 ms with a single pulse pack resulted in peri-electrode coagulative necrosis (PECN) zones and inter-electrode non-necrotic thermal reaction (IENT) zones in the dermis. In contrast, treatment lasting 5000 ms with 10 sub-pulse packs produced distinct IENT without notable PECN over a wide dermal area. Skin specimens obtained at 1 h and 3, 7, and 14 days after PCC-assisted RF treatments showed a higher degree of thermal tissue reactions in the deeper dermal regions compared to those after RF treatments without PCC.

Conclusion

PCC-assisted RF treatment, utilizing an invasive bipolar microneedling device, enhanced RF-induced skin reactions in the mid to deep dermis while preserving the epidermis and upper papillary dermis from excessive thermal tissue injury.