Efficacy and Safety of Three Needling Patterns for Microneedle Radiofrequency in Axillary Osmidrosis: A Prospective Randomized Trial

Summary

Axillary osmidrosis (AO) impacts daily life and mental health. Microneedle radiofrequency (MNRF) offers good results with fewer side effects than traditional surgery. A new zone-directed needling pattern was tested against two common methods. After six months, the zone-directed approach worked better, improving quality of life with fewer side effects.

Abstract

Axillary osmidrosis (AO) is a common dermatological disorder characterized by malodorous axillary secretions, which severely impairs patients’ quality of life and psychological status. Microneedle radiofrequency (MNRF) has emerged as a minimally invasive alternative to traditional surgical treatment owing to its favorable efficacy and safety profile; however, clinical needling patterns currently lack standardized, evidence-based criteria and largely rely on individual experience, potentially leading to inconsistent therapeutic outcomes and variable risks of adverse events. This prospective randomized controlled trial enrolled 90 patients with moderate-to-severe axillary osmidrosis to comprehensively evaluate the efficacy and safety of a novel zone-directed needling pattern (ZD), with full transverse needling (FT) and full longitudinal needling (FL) set as conventional control techniques. All participants completed a 6-month clinical follow-up, and therapeutic outcomes, quality-of-life improvements reflected by the dermatology life quality index (DLQI), and early postoperative adverse events, including erythema, swelling, and pain, were systematically compared among the three groups. The ZD needling pattern achieved high clinical effectiveness (90.0%) comparable to FL (93.3%), with a safety profile closer to FT, while FT showed lower 6-month efficacy (53.3%) and a higher recurrence rate (40.7%). The FL group, despite high efficacy, exhibited a significantly higher incidence of short‑term adverse reactions. The present findings demonstrate that the optimized ZD needling strategy effectively balances therapeutic efficacy and procedural safety by integrating the advantages of conventional longitudinal and transverse needling modes, providing a standardized, evidence-based MNRF manipulation protocol for axillary osmidrosis treatment.

Introduction

Axillary osmidrosis (AO) is a distressing dermatological condition characterized by malodorous axillary secretions that significantly impair psychosocial well-being and quality of life. The odor arises from bacterial metabolism of apocrine gland secretions, with severity correlating with glandular density and activity^1,2. Histologically, AO is marked by apocrine gland hyperplasia and an irregular three-dimensional distribution within the dermal-subcutaneous junction³, creating a therapeutic challenge for complete glandular destruction and contributing to treatment recurrence⁴.

Multiple treatment options ranging from topical agents, botulinum toxin injection, microwave thermolysis, to surgical excision have been applied for AO management, yet each modality carries inherent limitations, including unsatisfactory long-term efficacy, prolonged downtime, prominent scarring or high recurrence rates, highlighting the clinical demand for refined minimally invasive therapeutic schemes⁵. Microneedle radiofrequency (MNRF) represents an advanced minimally invasive modality that delivers controlled thermal energy via insulated needles to precisely target apocrine glands, with low recurrence and mild transient complications in clinical trials⁶. Operating by resonating with water molecules in glandular tissue to generate localized heat, MNRF achieves selective destruction⁷. Compared to surgical excision and other energy-based therapies, MNRF demonstrates satisfactory efficacy with reduced scarring, quicker recovery, and better cost-effectiveness. Despite consistent energy parameter settings during MNRF therapy, clinical observations indicate that the spatial arrangement of insertion trajectories, namely the needling pattern, exerts a substantial influence on the range of thermal injury and subsequent clinical outcomes. At present, there is no consensus regarding optimal needling strategies, and evidence-based, standardized protocols for pattern selection are lacking, resulting in clinical practice relying largely on individual operator preference⁸.

Given the anatomically heterogeneous distribution of axillary apocrine glands, this study hypothesizes that a regionally differentiated targeted puncture strategy could maximize gland destruction while limiting unnecessary thermal damage to normal periglandular tissue⁹. To address this, a prospective, randomized controlled trial comparing a novel zone-directed needling strategy (ZD) with full longitudinal (FL) and transverse (FT) patterning in patients with moderate-to-severe AO was conducted. The objective was to identify the needling approach that achieves optimal long-term therapeutic efficacy alongside the most favorable safety profile. The findings of this trial aim to provide standardized, evidence-based operational guidance for MNRF treatment of AO. The primary novelty of the present work lies in the proposal and head-to-head quantitative validation of an anatomically oriented, zone-directed needling protocol that balances efficacy and adverse event risk and addresses the lack of standardized puncture regimens in current clinical practice.

Protocol

Study design and participants

This randomized, patient- and assessor-blinded, parallel-group trial adhered to the CONSORT guidelines¹⁰. The checklist is provided in Supplementary File 1. The protocol was approved by the Ethics Committee of the First Affiliated Hospital of Chongqing Medical University (2023-435) and registered at ClinicalTrials.gov (NCT07094009). The study was conducted between October 2023 and April 2024 in the dermatology outpatient department. All procedures were performed in a dedicated treatment room maintained at a constant temperature of 22–24 °C. All participants provided written informed consent. Patients were randomly allocated in a 1:1:1 ratio to the FT, FL, or ZD group using a computer-generated randomization sequence. Allocation concealment was maintained using sequentially numbered opaque sealed envelopes prepared by an independent statistician. Participants and investigators, including outcome assessors and statisticians, remained blinded throughout the trial.

The primary outcome was the clinical success rate of different MNRF needling patterns in AO. Based on prior clinical observation, efficacy rates of 50% (FT), 90% (FL), and 90% (ZD) were assumed. Sample size calculation using PASS (two-tailed α = 0.05, power = 90%) determined 27 patients per group. To account for attrition, 30 patients were enrolled per group (total n = 90). Inclusion criteria: (1) age 18–50 years with AO; (2) AO severity Grade 2–3 per Park’s Grading System¹¹; (3) willingness to provide informed consent. Exclusion criteria: (1) concurrent axillary dermatoses; (2) history of keloid or hypertrophic scarring; (3) pregnancy, lactation, or planned pregnancy; (4) coagulation disorders or immunodeficiency; (5) a previous history of invasive axillary odor treatment. Of 100 screened patients, 6 did not meet the inclusion criteria, and 4 declined, resulting in 90 randomized participants: 30 each in the FT, FL, and ZD groups (Figure 1).

Procedure of MNRF

On the day of treatment, the axillary region was thoroughly cleaned, and hair was shaved prior to the procedure. Each patient was positioned supine with the arm abducted at approximately 90° to expose the axillary vault. Following standard disinfection and sterile draping, tumescent anesthesia was administered at the dermal-subcutaneous junction. The anesthetic solution comprised 20 mL of 2% lidocaine, 0.5 mL of 0.1% epinephrine, and normal saline to a total volume of 200 mL. A waiting period of approximately 5 min was observed to ensure adequate anesthesia. The treatment area was defined as a square extending 1.0 cm beyond the hair-bearing region of the axilla and then subdivided into 3 cm² grids. Each patient received a single treatment session. Treatment was delivered using an MNRF device equipped with a sterile, single-use tip. The device settings were fixed as follows: energy output at 15 W, pulse width at 300 ms, and needle depth at 4.0 mm. The needle penetration depth was adjusted to 4.0 mm to target the apocrine gland layer based on prior anatomical studies. The direction of needle insertion was accordingly defined as transverse (parallel to the basal skin folds) or longitudinal (perpendicular to them).

Patients were randomly assigned to one of three needling protocols: the full transverse (FT) group, in which transverse needling was applied across the entire treatment area (Figure 2A, D); the full longitudinal (FL) group, in which longitudinal needling was applied across the entire treatment area (Figure 2B, E); and the zone-directed (ZD) Group, in which a stratified approach was used (Figure 2C, F), with longitudinal needling restricted to the central region and transverse needling applied within a 1.5 cm peripheral band inside the marked border. All procedures were performed by a single experienced dermatologist to ensure consistency. Following treatment, the site was cleansed with normal saline, then a 30-minute ice compress was applied. The area was covered with sterile gauze and bandaged. Patients were instructed to keep the treatment area dry for 48 h and to avoid strenuous physical activity for 7 days. A detailed list of all materials, reagents, equipment, and software used in this study is provided in the Table of Materials. Generic institutional supplies (e.g., sterile gauze, disinfectant, and ice packs) were obtained from the hospital’s standard supply inventory.

Efficacy

Efficacy was assessed at 7 days and 6 months post-treatment. All evaluations were performed by two trained dermatologists who were blinded to group allocation. AO severity was graded on a 0–3 scale using the Park Grading System (PGS, Table 1). Treatment efficacy was determined by the change in the PGS score, which was classified as excellent, good, or fair based on a predefined AO elimination grading system (Table 2). Clinical success, defined as an efficacy grade of excellent, good, or fair, was based on published studies^12,13. Recurrence was defined as a decrease in PGS score at 7 days followed by a return to baseline or higher at 6 months. The Dermatology Life Quality Index (DLQI, range 0–30) was recorded at baseline, 7 days, and 6 months.

Safety

Safety outcomes were documented at 7 days (for acute, transient events such as pain, erythema, swelling, and ecchymosis) and 6 months (for long-term sequelae such as scarring and pigmentation, as well as the status of any early complications that had resolved) according to predetermined checklists. Pain was assessed using a Visual Analog Scale (VAS, range 0–10, where 0 = no pain and 10 = worst imaginable pain).

Statistical analysis

Statistical analysis was conducted using SPSS. Normality of continuous variables was assessed with the Shapiro–Wilk test. Normally distributed data are expressed as mean ± standard deviation (SD) and were compared using one‑way ANOVA with Bonferroni post‑hoc tests. Non‑normally distributed data are presented as median (interquartile range, IQR) and analyzed using the Kruskal–Wallis H test followed by Dunn’s post‑hoc tests. Within‑group comparisons were performed using the paired t‑test (parametric) or the Wilcoxon signed‑rank test (non‑parametric). Categorical data are shown as frequencies (percentages) and compared with the Chi‑square or Fisher’s exact test, as appropriate. For multiple comparisons among the three groups, the Bonferroni correction was applied consistently to all primary and secondary endpoints, with a significance threshold of p < 0.017. All analyses were conducted on an intention‑to‑treat (ITT) basis. Treatment effects for categorical outcomes were expressed as Risk Difference (RD) and Relative Risk (RR), while the Hodges‑Lehmann median difference was used for non‑parametric continuous data. All effect sizes are reported with 95% confidence intervals (95% CIs). A two‑tailed p‑value < 0.05 was considered statistically significant for all other analyses. Exact p‑values are reported wherever feasible; p‑values below 0.001 are presented as p < 0.001. Post-hoc sensitivity analyses using a stricter efficacy definition (excellent + good only) were performed to test the robustness of the primary results.

Results

A total of 90 patients were enrolled and randomized: FT group (n = 30; 17 female/13 male), FL group (n = 30; 16 female/14 male), and ZD group (n = 30; 15 female/15 male). Baseline characteristics were comparable across groups, with no significant differences in gender distribution (p = 0.875), mean age (FT: 25.3 ± 3.8 years; FL: 26.1 ± 3.6 years; ZD: 26.9 ± 3.7 years; p = 0.251), Body Mass Index (BMI, FT: 23.0 ± 3.4 kg/m²; FL: 22.4 ± 3.8 kg/m²; ZD: 21.9 ± 3.5 kg/m²; ...

Discussion

MNRF can penetrate deeply enough to reach apocrine sweat glands, shrinking and destroying them in a targeted manner by relying on the high-frequency thermal effect, while minimizing damage to surrounding tissues. This technique generates ablation and coagulation^14,15. Histological studies confirm a reduction in the number and size of both apocrine and eccrine glands post-treatment^16,17. T...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
0.9% Sodium Chloride Injection (Normal Saline)	Sichuan Kelun Pharmaceutical Co., Ltd.	China National Drug Approval No. H51021156	Specification: 100 mL: 0.9 g; used as diluent to mix lidocaine and epinephrine for preparing local anesthetic solution in microneedle radiofrequency therapy for axillary osmidrosis
Adobe Photoshop	Adobe Inc.	Version 2024	Software used for image editing
Epinephrine Hydrochloride Injection	Yuanda Pharmaceutical (China) Co., Ltd.	China National Drug Approval No. H42021700	Specification: 1 mL:1 mg, 10 pieces per box; mixed with lidocaine for subcutaneous injection to induce vasoconstriction, reduce intraoperative bleeding and prolong local anesthetic effect during microneedle radiofrequency therapy for axillary osmidrosis
GraphPad Prism	GraphPad Software, Inc.	Version 10.1.2	Software for plotting statistical graphs and visualizing research outcome data
High-frequency surgical electrode (treatment tip)	Peninsula Medical Co., Ltd.	Pure S4	EO sterile medical treatment tip,  applied for apocrine gland thermal ablation in microneedle radiofrequency therapy for axillary osmidrosis. This tip featured a 3 × 5 rectangular arrays of microneedles.
Lidocaine Hydrochloride Injection	Southwest Pharmaceutical Co., Ltd. (Taiji Group)	China National Drug Approval No. H50020038	Specification: 5 mL: 0.1 g, 5 pieces per box; local infiltrative anesthetic mixed with epinephrine hydrochloride injection for subcutaneous anesthesia prior to microneedle radiofrequency treatment of axillary osmidrosis
SPSS (Statistical Package for the Social Sciences)	IBM Corporation	Version 27	Statistical software for baseline characteristic comparison, efficacy and safety data analysis
United III Radiofrequency Therapeutic System	Peninsula Medical Co., Ltd.	United III-RF	Radiofrequency host system, matched with Pure S4 sterile microneedle electrodes for axillary osmidrosis ablation.